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  1. 2019 Silverado facelift 5.3 103000 kms getting the generic Misfire code when I scan it it shows service esc, service parking break and a flashing CEL. It has a rough idle and clunks hard when coming to a stop almost like being rear ended. This isn’t what’s weird it also occasionally billows white smoke out of the tailpipe for around 10 seconds this only happens about once every 2000 Kms. It also backfires occasionally and sometimes is a little extra Smoky the smoke isn’t blue it’s a thick white but doesn’t smell like coolant it smells like gas the coolant and oil levels also never change the normal exhaust also smells very rich spark plugs look fine I changed them and the coils dealership says they don’t know what’s wrong with it can anyone provide me some insight?
  2. Hello team, new to the forum and new to the GM truck world. Issue: truck seems to be misfiring under heavy load. The engine light will begin to flash and traction light comes on. After a minute or so, traction light will go off but engine light will remain. Codes cleared and drives fine until another misfire. No issues while truck starts. I’ve replaced the coils, wires and spark plugs. Cleaned up 4 grounds (ECM, and the 3 under the truck on the driver side). I’ve attached the codes present. P300 and rest all U codes. I’m at loss. If there is anyone experienced this please help! Next step is the stealership. link to video.
  3. Hello team, new to the forum and new to the GM truck world. Issue: truck seems to be misfiring under heavy load. The engine light will begin to flash and traction light comes on. After a minute or so, traction light will go off but engine light will remain. Codes cleared and drives fine until another misfire. No issues while truck starts. I’ve replaced the coils, wires and spark plugs. Cleaned up 4 grounds (ECM, and the 3 under the truck on the driver side). I’ve attached the codes present. P300 and rest all U codes. I’m at loss. If there is anyone experienced this please help! Next step is the stealership. link to video.
  4. Okay guys I bought this truck from a dealership in September. It was used and I got a 30 Day warranty. After the 30 day period, this is what’s happening. I got in my truck and noticed a rough idle. My truck would shake and out of no where the check engine light starts flashing and my traction control light comes on. I took it to my buddies and we got a P0308 Misfire Detected Cylinder 8. So I did some research.. I also had a code which was P219B. Air/fuel mixture ratio. I changed the spark plugs.. didn’t work. I moved coil packs.. the misfire didn’t move. So we watched Live data on the scanner and injector 7 was acting up. So we replaced all the injectors on that side and this truck is still missing.. I’ve ran seafoam through it and cleaned the throttle body and MAS. My buddy things I have a valve issue or something wrong with the cylinder… there is no AFM deleted or anything of that sort. The truck has worked flawlessly until now. 135,000 miles on it. The rocker arms all looked great. please someone give me something to try. I just want my truck fixed lol. posting a link below of what it’s doing…
  5. My Suburban has about 162K miles and has been meticulously maintained. Spark plugs and wires replaced at 113K miles. Brand new Wix air filter. BG or Amsoil fuel injector cleaner additive added to the fuel tank every ~5K miles. For the past 6 months or so I have ~5 totally out of the blue blinking check engine lights that go away after a minute or so. This always happened at cruising speed of ~72 MPH. I would pull over, run a scan, and only get P0300. That is, no specific cylinder is reporting any misfire. Checked all live data from all sensors I could read- MAP, MAF, O2, barometric pressure, and fuel pressure- and they all show normal readings at idle and under load. I understand that problems don't go away on their own and at one point have to go to the dealer. However, I am trying to do some of the low hanging fruit diagnostics myself consider the intermittent nature of this issue. Any suggestions what specific protocol to follow to narrow the cause of this random misfire? Thanks!
  6. My 2013 Silverado 2500 has been misfiring & jerking under acceleration for a little while now & the CEL finally came on last night at startup. I took it in to Autozone & it showed for P0442, small evap system leak, canister purge valve, with the recommendation of replacing the evap emissions purge solenoid.. Could this be the reason for the misfire &, more recently, random gas smell? I'll attach a pic of the print-out. Also, not sure if it means anything, but is there something wrong with the ABS too?? There's no code but I just don't get why it would be on the print-out then... Thanks in advance!
  7. Short version: 2018 silverado 2500 6.0 intermittently misfiring on bank 1. Holes 1/3/5/7. Changed 02 sensors, plugs. coils, catalytic converters, spark plugs. Once the truck is above 1300rpm or so, it doesn't misfire at all. Cannot seem to find any relation between whether ambient temperature is hot or cold or when engine temperature is hot or cold. Long version: Hey Y'all, I bought a used 2018 Silverado 2500 with a 6.0 L96 "G" about a month ago. Used from a sales lot. 160km (100,000 miles.) After driving about 200 highway miles or so, I was at a red light, and it was idling (burbling and chugging) a little weird. When I went to leave the red light, the engine was a bit hesitant, but once above 1200rpm or so, it drove fine. Over the next few days, It did the same thing intermittently and ended up throwing some codes: P0420: Catalyst system low efficiency P0137 H02S Circuit Low voltage sensor 2 P2097 Post catalyst fuel trim system high limit bank 1 P2099 Post catalyst fuel trim system high limit bank 2 P0300 random/multiple misfire. However, once rolling, it performs fine with no drama. The dealer gave me a 2 year unlimited mileage powertrain warranty through a 3rd party company. The warranty company does not pay for diagnostic work, just part changing and part cost. In order to get this warranty, I agreed to do oil change/spark plugs/air filter. For peace of mind, I ordered new 02 sensors (2 up 2 down) 8 new plugs (stock replacements) ignition coils and ignition wires. Once the parts came in, I got underneath and changed the 02 sensors. It looks like they had been changed at some point because they were aftermarket sensors. I started the truck up and cleared the codes. It ran fine for 10 minutes. I had my fiancée come out to back the truck out of the garage (I was filthy) and as soon as it went in reverse, it started idling like dog sh** and stalled out. I started it up again and we coerced it out of the garage. At this point I was tired and cranky (up for 24 hours with 12 hours of work in there.) I was in no mood to carry on with working on it. I took it to a shop and we plugged the Gucci Snap on scanner into the truck. It showed it was misfiring on 1/3/5/7. All bank 1. Bank 2 was fine. The mechanic/shop owner and I decided to have the coils/plugs/wires changed and see what happens. He called me later that evening and said the truck was running like a top. He had his datalogger on and it hadn't recorded a single misfire. I went to the shop and saw the truck had been running for about 40 minutes without recording a misfire. Drove it 10 minutes to a friend's house and had dinner. It worked fine. No idle or low RPM acceleration issues. When I left his house, I let the truck run for a minute and it started repeating it's prior behaviors. Did some studying at youtube university. Added a 2nd ground off of the coil harness to ensure it was grounding properly. No change. Cleaned MAF and throttle body, no change. Called some friends that are smarter than me. We concluded it may be the catalytic converter. While the truck wasn't short on any power.. It was a company truck (seemingly well maintained) that likely idled a lot. There are nearly 7000 hours on the truck. Not sure if that's high hours for the mileage. Took it to an exhaust shop and asked them to determine if the cat was pooched. They called me back and said it was. I did not ask how they determined this. Ordered a new set of Magnaflow cats (and a muffler for fun sounds.) Had them installed yesterday. Picked them up from the shop and the truck ran great. Today, it started doing the Harlem shake again. I'm guessing after this... It's got to be a wiring issue? Chafing somewhere? What makes me have a hard time believing it's electrical is that it is strictly RPM related. Idle to about 1300/1400 rpm. And intermittent. Once I'm cruising it's fine. If I am at a lower speed and the trans is in a gear where the RPM is low... it will (very seldom) struggle a little to build RPM. I've been using the gear selector a lot to keep the RPM's above 1400. I cannot seem to find a correlation between when the engine is hot/cold etc. If any of you have some insight, it would be greatly appreciated. This weekend a friend and I are going to hookup datalogger to check fuel trims, and also watch for misfires while wiggling harnesses and such. Have a great day! I'm about to lose my mind. This has been a slow process
  8. I recently bought a used 2016 Sierra Denali 5.3L 4x4 in March with 48k miles. Truck has been great until yesterday (now 52k miles) when I ease into the gas it shudders and shakes like crazy until i punch it. The tach is bouncing up and down and it doesn't matter if it's in v8 or v4. It almost feels like it's a misfire but it's weird that it only does it when I'm easing into the throttle or going uphill. The truck has the 8 speed transmission. Has anyone else ran into something like this and would the manufacturer warranty cover the fix for this?
  9. I have a 2014 Silverado LTZ, with a 5.3L engine. There is approximately 145,000 miles on the engine. I have a misfire on the #3 cylinder. I have replaced the induction coil on the #3 cylinder, but I still have a misfire on this cylinder. My mechanic says that the lobe on the camshaft is worn and the camshaft needs to be replaced. I would think that if the lobe on the camshaft is bad then other lobes would also be bad, a defective camshaft. Has anyone else had this problem? Does anyone have any suggestions as to what might be causing the misfire. Thank you in advance for any advise the you can provide. Julian.
  10. (I posted this on another board, if you've seen it there and replied then disregard. ) Hey folks, I’m new here. I’ve been reading post for a while, my vehicle before the 2010 Tahoe I now have was an ’03 Tahoe. I’m looking for input on a problem I can’t wrap my mind around. A quick bit of info about me, I’m one of those older guys from the days of points and condensers and manually setting your timing (1970’s era) etc. I never built ‘hot rods’ so I never got deep into the technical side of things, but I have rebuilt 3 or 4 engines over the years and usually do all my own repairs. I’m not into engine modifications, pretty much an OEM spec kind of guy. I do commercial low voltage electronic systems for a living, so I have no problem with automotive electrical, and have a decent understanding of module control of inputs and outputs. I’m not a pro at this by any means, but I’m also not a newbe. No doubt you can get over my head if you happen to be a pro and have some input, but hopefully you won’t have to candy coat it too much. So back in November, I traded my ’03 Tahoe in for a 2010 LT Z71 Tahoe with a 5.3 and 120,000 miles. I plugged in my cheap code reader and there were no codes and all the monitors were ready, and it ran fine, so, no need to fix what’s not broken. I wasn’t real pleased with the mileage, it averaged a little better than 13.5 mpg, but figured I’d work on that as time went on. I did put new plugs and plug wires in the first month. Back in April it started idling rough, but didn’t throw any codes. Knowing it’s 8 years old with over 120,000 miles, and not knowing the history, I don’t have a problem replacing parts so I’ll know what I have, especially anything that will help gas mileage. I replaced the throttle body and position sensor (along with the accelerator pedal w/position senor), and once the idle speed settled down it was still rough, and threw a P0305 code (cylinder 5 misfire). I’ve been fighting that code ever since. I have a scan tool, I can see the misfire counter add up on cylinder 5, and it seems to be only at an idle. I moved plugs, plug wires, coils and injectors to other cylinders, but the misfire at idle stays on cylinder 5. I researched the hell out of Active Fuel Management, which I have, and I know all the lifter issues and problems they can have, but AFM is on cylinders 1, 4, 6 and 7, and my misfire is on cylinder 5. It’s not consuming oil like the ones with the AFM lifter problem. I’ve replaced the Mass Air Flow sensor, MAP sensor, water temp sensor was replaced when I changed the water pump back in February (shaft bearing was starting to squalk), I changed the oil pressure sensor (and the VLOM screen underneath it) just to be sure the oil pressure reading I was seeing was accurate. I changed the vapor canister purge valve and vapor canister vent valve (problem with gas pump handle disengaging while filling the tank), I changed both the crank and cam position sensors (and did the crank position relearn), still have the misfire. I’ve checked compression with all the plugs out, over 180 pounds on every cylinder, including cylinder 5. I checked vacuum (inserting a ‘T’ at the brake booster vacuum connection) 19 inches at idle, goes to 17 inches if the AC is on. I have a noticeable loss in power, most of the time it feels like I’m towing a pontoon boat. My gas milage is down around 12 mpg or less. I noticed on my scan tool the long term fuel trim on bank 2 was running about +12 at idle, but would go down to about +1 while driving, while not the same bank as cylinder, assumed I had a vacuum leak on bank 2. I also noticed O2 sensor Bank 1 Sensor 2 constantly stayed around 810 mV regardless of what the others were doing. Thinking the O2 sensors may be the original ones I went ahead and changed them. I suspected that if they were getting old and slow and sending bad info to the ECM, that when it was open loop (with a vacuum leak) and then going closed loop and seeing bogus info from the O2 sensors and making fuel adjustments for that that it was constantly changing fuel mixture as it bounced in and out of open and closed loop mode, which I thought may be why it was so sluggish. I decided to change the intake gaskets, went with Felpro. While I had the intake off I went ahead and changed the fuel injectors. The long term fuel trim is back down low again so apparently I did have some vacuum leaks. And now I feel better about the fuel injectors actually delivering what the ECM thinks they are delivering. But, still have the misfire on cylinder 5 and recurring P0305 within two drive cycles. I can pull the injector electrical connector off cylinder 5 while idling and it really doesn’t change the idle speed. At that point I was suspecting maybe the ECM is stuttering on the pulses to the cylinder 5 injector. I put a noid light on the injector connector for cylinder 5 and at an idle (when the scan tool is steadily counting misfires on cylinder 5) I’m seeing a nice steady light pulse not missing a beat. I put a spark indicator on the spark plug, same thing, steady light pulse, not missing a beat. Now, off with the valve cover. Cranking the engine over I can see both valves on cylinder 5 open and close as they should. I put #5 at TDC and removed the rocker arms, no visible damage, no cracks, no wear. Pulled the push rods, not plugged, you can clearly see light thru them and their walls just like looking through a new straw. Both valve springs look fine, neither is broken, both seem to be keeping the valve closed tightly. That didn’t satisfy me, so (after reinstalling the rockers) I hung the coil pack with some string, reconnected the harness and plugs and started the motor to watch the rockers in action. Neither valve missed a beat, both opening and closing the same amount as the other valves by just watching them (I’m sure there’s probably a scientific way to measure that, but with the naked eye they appear to be working just fine) Both pushrods are pushing out oil on top of the rock arm, not tapping any louder than the other, so I’m thinking the lifters are. I got my stethoscope and listened to the fastening nut on all 8 rocker arms. I will say this. On seven of the eight rocker arms you can hear that whirring sound of the engine and a slight tapping sound as the valve operates, but the exhaust valve of cylinder 5 was a little louder and sounded kind of rattley in between taps. Not extremely louder than the others with the stethoscope, but enough to notice it was not as smooth and quite as the others. BUT, still opening and closing the valve and pumping oil. And with the naked ear, it’s no louder than any of the others. I found a TSB (#11-06-04-007B) about changing the throttle position sensor that said for Tahoes from ’08-’10 if you put a new throttle position sensor that you MUST reflash the ECM with he latest software, but from ’11 up the reflash was not required. Mine is a 10 and I have changed the throttle body/throttle position sensor as and assembly, so I put the old one back on for now just to be sure that’s not causing an issue. So I’m at a loss. I’ve used all ACDelco parts (except for the Felpro intake gaskets) I’ve eliminated every external thing I can think of that could cause a misfire, I have compression, vacuum, fuel pressure running 58-60 psi key on and engine off, and stays around 58 psi at idle, no vacuum leaks. The one and only thing I’ve found wrong with cylinder 5 is a little extra noise on the exhaust rocker are when listening with a stethoscope. I may be wrong, but I can’t believe THAT is enough to cause a constant misfire since the valve is opening and closing as expected. The only thing I haven’t changed is the knock sensors. Starting in ’07, they moved them from underneath the intake to down on each side of the of the lower block. Easy to get to now, and ironically the one on the left side is about where the #5 cylinder is. The scan tool shows no knock on any cylinder. I really don’t thing a bad knock sensor would cause a cylinder specific misfire, but they are less than $8 each at Rockauto, so I ordered a couple of them. On a side note, I’ve also ran some Seafoam in the oil for about 200 miles thinking if the problem was a lifter it would loosen up. I haven’t tried Marvel Mystery Oil yet. If you have any input that would help I would appreciate it. I’ve seen posts about misfires on discussion boards, but most of the time there is no follow up post if they fixed the problem. If I find a solution I will absolutely post what I did to resolve it. Thanks for reading if you got this far, sorry it’s so long.
  11. Hi. I bought a new 2021 AT4 March 5. 20 miles on it. Drove home from the dealer (4 miles) and the next time I turned it on, CEL and OnStar diagnostics emails me to take it to the service department. They say they reset MAP sensor and send me on my way. Later that day, same thing happens. I take it back in, they say MAP sensory needs replacing. They had it almost 2 weeks waiting on the part. After they replaced it, everything went fine for about 1200 miles and then I get blinking CEL for about 30 seconds then it stops. Next day, blinking CEL for a minute or so, and then it turns solid. I took it back to the dealer and they say the only code pulled was P0300 misfire. They have no idea what’s causing it, and quite frankly I’m pretty fed up at this point. They’ve had my new truck longer than I have in the month I’ve owned it. Has anyone had something similar happen?
  12. I have a 2020 gmc sierra sle 5.3, I bought it may 13th. Starting at about 800 miles check engine light would flash for a minute or two and then go off, this occured every 300 miles until I got in one day around 1500 or 1600. Check engine light stayed on. Called the dealership and took it in was throwing misfire codes, the diagnosed it as fuel pump module reset the codes and ordered the part and sent me on my way. Come back in and had it replaced when the part arrived, well now fast forward to a tank and a half later and now the check engine light is on for the evap system/gas cap, and fuel pressure at 2200 miles. Right at a week from the time it come out of the shop. I've been extremely happy with the truck but I can't believe I'm going to have to find time to get it in the shop to be looked at and fixed again. I'm at wits end already. Anyone else having these issues?
  13. Okay so I have a 2008 GMC Sierra with 130 on a 5.3. It's my daily driver and now has some issues. Basically a misfire in cylinder 2 that I would like any good help with before I keep trying new things that might not work. So the stalibitrak and traction control lights also flash and are on regularly which started at the same time. Meanwhile the engine light has flashed for a couple seconds but is usually solid. It is a p0302 misfire. So far I have cleaned the MAF, checked for leaks, changed all spark plugs, coils, and wires, ran some seafoam through it at the brake booster line and some in the gastank. I pulled the new spark plug after it didn't work for inspection and it was very carbon fouled after 3 days and very little driving. It runs good at higher speeds but idles rough and loud I would say klunky. Has not stalled. So Does anyone have any ideas before I keep changing things that are not the problem? 2008 Chevy Silverado/ 08 GMC Sierra 5.3
  14. driving a 97 k2500 camper special, 4l80e with 454 vortec couple days ago I got in my truck after work and noticed it would stumble when hot, 100C no problem but a little bit warmer and i would have issues. always under load during acceleration. got home and idled in drive and it felt like an obvious misfire, RPM would drop to about 500. pop it in neutral or park and no misfire or stumbling, its been confusing me since in the mornings when i pull it out the garage it has no problems all the way to work (5 minutes highway and 5 minutes city) but end of the day and evening- same issue bought the truck with 268km now has 276, oil change every 5000k. did fuel pump (48psi at idle now) FPR, distributor cap and rotor, plug wires and plugs, ran seafoam through the intake and in the fuel tank. ive heard of distributor gears going south but id assume then i would have the issue when cold too. runs like a top at any temp below 100C, no engine light, plugged the scanner in anyways and no codes whatsoever. any help is appreciated, looked through forums for a couple days now but nothing exactly like what I'm experiencing. kevin,
  15. I did a search here for it but came up empty. Last week, my Check Engine Light came on briefly while on the highway. Just before and after that I noticed a reduced lack of response to giving it more throttle. I had a local guy pull the CEL code and said it came up as #7 Cylinder Misfire. I'm at 55,000 miles and am off warranty. The truck is a '14 with a 5.3. Any suggestions, or thoughts how serious this may be ?
  16. Hey all, so I have a 17 Silverado 5.3. 33000km was driving around yesterday. Truck was at operating temp and trans temp was at 76 so all was good. it was driving fine, then I got home. And backed into my driveway. Parked emptied groceries yadda yadda. 5 minutes later realized I had to pull in. Got in, and did just that. Then 5 minutes later had to run to corner store. This is when the truck started rough and check engine light started blinking and it was like I had no power. ( and when I say rough, it was god awful. Like bucking and lurching) Turned around a parked it. 2 hours later drove it 40km and not an issue. Next morning drive to and from work (7km each way) no issue. some say it can be the anti theft , or dirty injectors or worse clips or plugs. Trucks only got 33k help?!
  17. Looking for help/instructions on replacing fuel injector/s for a 2017 5.3L Silverado. Truck has 80K miles on it and a #5 misfire. Dealer ran a diagnostics and said the injector needs to be replaced. I found a couple pictures on the forum of the fuel injectors but very little information on steps to replace them. The only videos I could find online were for older models with a different injector diagram. Talking to the dealer they quoted me $770 to replace a single injector, gaskets and piping associated with the job. 4 hours or labor and $240 in parts. Are there any good instructions or videos out there on replacing fuel injectors on a 2017 Silverado? I've never done a job like this but consider myself mechanically include, is this an easy enough job or should I leave this to the dealer to do? I know they say if your replacing a single injector you might as well replace all 4 on one bank but is that really necessary, $110 a piece and if the other 3 are fine why replace them? The dealer said the piping and gaskets must be replaced even for a single injector replacement job. Is this all necessary? I've never had another vehicle with injector problems so this will be a first. Parts quoted- 12687650 (1) injector 12626354 (8) gaskets 12677002 (1) pipe 12677004 (1) pipe Any help, links to instruction/diagrams or videos would be awesome! I enjoy working on these projects rather than paying someone else to do the work since you learn something every time. I also want it done right. Thanks all in advance!
  18. I'm having a bit of a dilemma here. I have a 98 Yukon and back in January it started missing. I replaced the plugs, wires, cap, and rotor, and it worked fine for a while. A few weeks ago, it started missing again, this time much worse. I replaced the O2 sensors and that didn't fix it, so I took it to the dealership to have it diagnosed. The dealership said that the distributor and the injectors were bad. I replaced the distributor with one from a salvage yard, and upgraded the old spider to a brand new AC Delco MFI injector system. I just finished replacing the injectors yesterday morning. I cleared the codes and took it for a drive. It all seemed fine, but then I noticed a slight hesitation and sure enough it showed the same misfire code. At this point I feel like I've done everything I can. When I put the intake back together I noticed a few things. One is that one of the screw holes on the new distributor is stripped, and wouldn't tighten down all the way, so I'm wondering if a slightly loose cap could be having an effect, and I'm also wondering if the plugs could have gotten messed up while the engine was missing really badly and if I should replace them again. I didn't replace the MAF senor when I did the O2 sensors, and I'm wondering if I should have, and I'm also wondering if I should take out the salvaged distributor and replace it with a new one. I found a good deal on one through Amazon. Knowing all that, is there anything else that could be causing this slight hesitation after all the work I've already done? Thanks in advance, Eric
  19. Hey guys and gals, Long time creeper, first time poster. I currently have a 2011 silverado 1500, with 163,622 miles on it. It's a 5.3 vortec engine. It smokes from the exhaust a light blue exhaust that's mixed with a grey/white exhaust. It stops smoking after roughly 10 seconds of running. Haven't noticed it while driving. It also doesn't smoke every start-up. It rough idles when in park. I replaced the plugs and wires a couple weeks ago, and I started misfiring on cylinder 8 after the change, before the change it was cylinder 5. The only codes it's thrown is for the misfiring. I also pulled plug 8 after the codes to check it and found oil on it. I did a combustion gas leak test and the liquid stayed the same color (blue). I'm starting to lose my mind. Any thoughts, suggestions to try? Also, as of now....I've noticed no loss in power at the moment.
  20. i could use some advice.... I bought a 2014 GMC Sierra crew cab z71 4x4 and my check engine light flashes so i take it to the dealer. Truck has 5k miles on it. Dealer says it is a misfire on cylinder 8. They tell me it had a loose clip on the spark plug. 500 miles later the check engine light flashes again. Go to the dealer again its a misfire on cylinder 8. They replace the plug and the wire. Said it was a bad plug. 500 miles later the light flashes again. I call the dealer and they tell me they will have to teardown the enging to cylinder 8 to see what the problem is. Does this sound right for an engine with less than 7k miles to need a teardown to cylinder 8? What does that all consist of anyways i ask? The serive guy never gave me a straight answer and wouldnt tell me what the compression was on that cylinder. I dont like the sounds of teardown a new engine and asked for that coil pack to be replaced and was told no. Anyways anyone had any problems similar to this and could offer some adive or tell me what a teardown to cylinder 8 consist of? Thanks
  21. First time posting but have searched the forums for years and have always found what I needed. Well this time I'm stumped, so I have a 1994 gmc k1500 pickup with a rebuilt 350 tbi bored .030 out with a stage 2 cam and long tube headers. (About 4000 miles on engine.) new distributor, plugs, wires, vss, So here's what's going on, the speedometer jumps around super erratically but when I turn the heater on it seems to change how much the speedo jumps around. If its on high it jumps around the least. Low or off its just bouncing off 85mph like bouncing to the point I can hear it slamming into whatever stops the needle from going any further. When I turn the turn signal on left it makes the radio light dim with each flash. The odometer turns constantly when while sitting in park. I have replaced the vss at the very end of the trans where the rear drive shift meets. I was drive the other day and the truck just didn't want to move seemed like it was just constantly back firing or misfiring. I have been trying to check all the engine grounds but not sure what all needs to be grounded. Any info/advice would be greatly appreciated.
  22. My 2008 5.3L 4WD Avalanche with ~135K miles has recently been throwing a P0306 cylinder 6 misfire, along with a Stablitrak warning. It first happened a couple weeks ago but only lasted a day. I cleared the code and it was fine for another couple of weeks before it happened again today. It does go through a lot of oil (probably a at every 1,000 miles), and there is a clicking sound. I know from researching this the last couple weeks that its likely failure of the #6 cylinder lifter and/or plug fouling due to the AFM system design and/or old PCV cover. I intend on doing some diagnostics this weekend including inspecting and replacing (if needed) plugs/wires/coils, doing compression tests, and pulling off valve covers to look for stuck lifters/valves. My questions are: 1) Other than the obvious, is there anything else I should be specifically looking out for when running these tests? 2) Are there are any other diagnostic tests I should be doing while I am in there. 3) Assuming compression test is fine, and replacing plugs/wires stops the misfires, can I hold off on replacing a bad lifter if there is one? 4) I would plan on getting a Range tuner to disable AFM (which I should have done when I bought the truck 3 years ago) and replacing the valve coverwith the new one. If the compression test is OK suggesting there is (currently) no ring, gasket, valve, etc. damage, would these measures stave off more issues? 4) If a lifter is bad and I really need to replace it now, can I just replace the one, or do I need to replace them all? Also, how difficult is it to take the passenger side head off to access the #6 lifters? 5) If it does fail compression, am I likely screwed and looking at a rebuild or replacement? 6) Any other advice, recommendations, or thoughts? Thanks in advance!
  23. So I am at a loss here. I have had an issue with my 2012 Silverado 1500 LT where cylinder 1 eats spark plugs for whatever reason. No big deal I just keep a spare and swap them when I need. That’s happened 3 times since I’ve owned it. The other day I am on the highway running probably 75 when it started running rough, tapping and the check light started flashing. The tapping was like a pen on a desk not a knock. I pulled right off and checked the oil and no. 1 plug. Oil was a lil low and I swapped the plug but the problem persisted. I drove it another 15 miles doing 55 and the light changed to solid and the misfires and tapping went away. I still have a light on solid reading the codes p0300, p0466, and p0300. I am inclined to change plugs and wires along with an oil change. I still have oil life left and is full synthetic and I did plugs and wires a few years ago. Has anyone had similar experiences?
  24. Hi there, new to the forum. Looking for information if someone already deal with this problems. 2014 Silverado 5.3 I changed spark plugs, cables, all the injectors. And after that the truck worked well for 2 days after that I started getting code for misfire cilynder 4, the stabilitrack light, engine power reduce, I know I need to remove the valve cover and check for lifters, but I just want to know if someone already deal with this and what was the fix for this. I like the truck but it just sucks to many issues with this engines. Thanks.
  25. 2007 Silverado 5.3 V8 with AFM with 180,000 miles Truck had lifter ticking sound and white smoke upon every start up which would go away after a few minutes, no check engine light Replacement list : - headgasket - valve gaskets - upgraded drivers side valve cover - valve stem seals - intake manifold gasket - exhaust manifold gasket - 8 new afm lifters - 8 new non-afm lifters - head gasket bolts - engine coolant temperature sensor - spark plugs - spark plug wires - fuel injectors - water pump - thermostat - cam sensor - crank sensor After completion of engine reassembly no longer had white smoke upon start up and no ticking sound but flashing check engine light code p0300. Code p0300 was for cylinder #1, #4, & #7 Moved coil packs between cylinder #1 and #2 to see if coil packs was bad but no change. Set engine at TDC before installing the rocker arms. All bolts have been properly torque and no parts have been left unplugged or uninstall. Any possible advice would be helpful
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