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  1. I need some help I’m not a mechanic totally but I have been going to school for it and my 03 Silverado 5.3 is misfiring and I don’t know what the problem could be I replaced the spark plugs coils and all the cylinders are getting spark and I had a compression test and the the cylinders have near perfect compression so I don’t think it’d be that. I even replaced the ecu/pcm in it and nothing changed it’s a hard idle and had no power can’t even make it a block really it also dies when I hit the brakes after going anywhere over 5 mph.
  2. Fixed! See page 2 update. Rebuilt Trans! 2014 Sierra 1500 5.3 120k miles Hey all, I searched and read some of the transmission threads but it wasn't helpful so hoping someone can guide me or had the same issue.. Truck has been running great no issues, one morning i go to work as usual and half way into the commute i get this skipping/shudder when under load. I let off it goes away. RPM is steady at idle and its not doing it or is not noticeable in cruise. No codes. Does it in Manual, all gears and all speeds. Only when i get on the gas. Power is less, it feels like a slipping trans but also feels like a misfire. Plugs are assumed to be originals so tonight im replacing all to see if it fixes it, if not: they needed to be done anyways so no harm done. Trans has been flushed at 95k at GM dealer. My next option is another flush. Any ideas?
  3. I have a 1993 GMC Sierra C1500 v6 4.3L with an automatic transmission and i have tried replacing the distributor cap, router button, spark-plugs and the module that sits under the distributor cap but nothing works it just rolls tries to kick and if it does start it dies instantly. also when trying to start it smoke rolls out of the throttle body I have no clue how to fix this
  4. Hey guys, first post on here and I've got something that stumped me 100%. I have a 2005 silverado 1500 flex vin code Z. It Idles rough it has terrible acceleration, wide open throttle it takes off like nothing is wrong. It misses on 7 every time, misses on 2 every other time, every other cylinder misses here and there. No misses when in park and rpms are kept about 2500. CEL flashes most the time when accelerating (except WOT) otherwise the light is on solid. It has 220k on it and I have replaced alot of parts. New parts All 4 02 sensors OEM Plugs OEM wires OEM Fuel pump OEM Throttle body cleaned 3 stage fuel system cleaner BG Brand Air filter believe it or not OEM again New transfer case (unrelated issue) I have covers the base of the intake with brake cleaner multiple time, no signs of leaks. I've had the smoke machine hooked up 3 to 5 times and again no signs of leaks. At this point what is the best route to take? Remove intake manifold so it's easier to get to and replace the main grounds behind the heads and replace gasket at the same time? Replace the pcm? Replace throttle body maybe? Any other suggestions or recommendations would be greatly appreciated.
  5. Good Evening, Gents. I hope all is well. Let’s get started with a little introduction of myself. My name is Cody and I’m new to this forum. I’m a long-time active member of other forums with previous vehicles. A year and a half ago I traded in my 2001 Z06 for an 07 Silverado. Extended cab, Flex Fuel 5.3 with 78,000 miles. 1 owner and a VERY well maintained vehicle. The truck has done me very well and is extremely dependable (duh; Chevy and the 5.3). About 4 months ago I started having a random misfire issue when traveling between work and home (~300 miles each way on the weekend). I had a minor misfire/hesitation and a check engine light. It wasn’t flashing, so I drove into the next town and had it checked. It was a p0352 and p0300 code. I got to my trailer where I work and changed the plugs and coil pack that it was indicating was the issue. It cleared up for a bit and then the p0352 returned. I swapped the coil pack with a different cylinder, along with the spark plug wire as well, and the CEL return. Same code. I’m sort of at a stump for what it could be as some people have said ground issues, wiring issues, etc. I’ve always been mechanically savvy and have maintenanced my own vehicles and have repaired/modified them. I’m really just seeing if anyone has had a similar issue and what their outcome was. The truck has a very intermittent miss. Sometimes it drives and runs great, then out of the blue with stumble and fall on its face. It’s very inconsistent. Any insight would be awesome. Thank you so much.
  6. So I had a few after market parts installed on my 2015 Silverado: Flowmaster 40 series, Volant cai and finally some Gibson performance headers (heat wrapped and all). I didn't have any issues until the headers were installed. Shortly after leaving the shop my truck isn't shifting correctly and my engine light is on. I figured over heating was the culprit and that I should let it cool down before taking it back out for some fun. Hours later the problem is persistent and my truck is down shifting at too high of rpms causing it to jerk and stall for a second. I also feel like there's some power loss. I plugged in my Diablo inTune i2 and it showed the error code being a 3rd cylinder misfire and rough idle. I checked all of the spark plugs, the wires and all the bolts but I can't see an issue with any of them; all the plugs tested good and all the bolts are secured. Does anyone have any insight as to what the problem could be?
  7. I know I've seen post similar to this got a 2014 chevy Silverado 5.3 with a lot of issues been thru two different dealerships in last week. Truck was stuck in limp mode they replaced coils fuel injectors amf lifters and the modular that kicks it into 4cyl mode....now it still shifts hard (like it's in limp mode still) does not go into 4cyl mode at all and vibrates between 1300 and 1700 rpm range along with my dash looking like a Christmas tree with all the lights on ....just hit 70000 miles...everytime they put it back together there is another issue with another cylinder....any suggestions would be appreciated
  8. Hi guys and gals. Just recently got a 2003 Sierra 1500 4.8 4x4 z71 extended cab with 300,000km on the clock. Ive been noticing it hard on gas and idle isn’t really smooth, especially when it’s colder sometimes I can see the tac jump a little. When it’s cold sometimes the engine light will flash for a few minutes. But when it’s cold sometimes the fuel gauge goes to empty and sets the gas light on and then comes back to normal after a minute or two. Use to have issues with four way randomly coming on, but that stopped for now so far. So so far I have swapped two different fuel pumps (both came from tested and running parts trucks) , new ngk wires, new ac Delco plugs sometimes you can hear what I think is a sparking noise from the passenger side. I dont have a lot of money and trying to fix this without a garage. Any help be greatly appreciated. I hooked up my phone and torque app and have attached the error codes and some data the app gave me. I just dont don’t want to be throwing parts at it trying to guess what’s wrong. Thanks for your time!
  9. Hello, I looked 2008 GMC Sierra 1500 that I was interested in purchasing with the 5.3L V8 has 174,000 miles. Truck runs rough at idle, rpms are fluctuating. Check engine light is on with codes P0300 and P0301. Can’t troubleshoot the problem. Coils, spark plugs, spark plug wires, new O2 sensors, new catalytic converters. Guy says that rockers all move so it isn’t Active Fuel Management lifters and he says 150 psi of compression across all 8 cylinders. Truck was at dealership, dealership says problem with cylinder numbers 1 and 8 the P0301 explains problem with cylinder 1 but why isn’t code P0308 being thrown? What else could be the problem?
  10. Hi guys, I need some help. On Thanksgiving I had remote started my truck to go make the last minute run to the supermarket. As I left my house to jump in and take off, I found the truck’s engine had stopped. When I started the truck with my key, the check engine light was on. I took it over to my local dealer and after a week and a half, I was told my aggressive treads (Nitto Trail Grapplers) could be the cause. The work order stated the tech swapped out my wheels and tires for a set of factory wheels and tires and could not get it to misfire. The work order also stated that code P050D was found. I did read in several treads this has come up and injectors was normally replaced. My truck was purchased in Oct 2014 and had 25606 miles on it when I took it in. There are a ton of lifted, leveled, stock trucks out there with the same tires so was wondering if anyone else had this issue. It’s really hard to accept that my tires (which has been on since 2014) is the cause.
  11. How's it going, I have a 2000 single cab 4.8 Silverado 1500 that has a misfire, gradually revving up the engine you can tell the engine is missing and causes truck to vibrate, and vibration is worse while driving. Has following codes: p0300, p0137, p0141, p0157. I believe these are codes for random engine misfire and various 02 sensors? If someone could point me in the right direction I would really appreciate it thanks
  12. New to site but I've got problems with my work truck I recently bought a long block 5.7 vortec from summit. And I also bought the updated fuel injection setup I also replaced the fuel pump the mass air flow sensor and fuel filter. It ran about thirty min. And developed a hesitation when I come to a stop then I would have to feather the throttle and it eventually would snap out of it and accelerate normally. So today I drove about twenty miles out to a place I ride dirt bikes and it was the same thing hesitated at every stop light until I got back into town and stopped at the only light and then it started missing and sputtering instead of hesitating and it is strange because it idles fine soon as I try to give it gas it starts dropping one or more cylinders and it doesn't stop missing I checked the wires and distributor cap rotor they looked perfect I did replace the distributor when I changed the motor also so it has maybe 3000 miles on it as well as the motor fuel pump water pump. I just changed the mass air flow with a new one last week. It's not showing any check engine light but I can barley get it to go. It misses so bad if I give it more gas pedal I intermittently back fires through the intake sounds like I'm am stumped I check the grounds I checked for vacuum leaks I need to get this thing running it's the only thing I have to drive for work. And I took last week off to fix the rear axle and put new brakes on the van along with new fuel filter and. MAF SENSOR. Please if someone can help it would be great to have this thing fixxed so I get my jobs finished thanks
  13. Hey guys have been battling this truck for a wile now and I'm kinda out of ideas and I don't want to keep throwing money at it so i figured maybe someone here could help. The truck is a 2003 GMC Sierra 2500Hd 6.0 Gas motor with 189,000 on it. It has a intermittent misfire the only codes i pull are a U1000 and a code for the bank 1 sensor 1 02 i have replaced that sensor a few times and it always comes back to misfiring. I guess it is possible that the sensors are bad out of the box but i dont seem to think so. I have replaced Fuel pump and filter, Injector 2 and 7 I have access to the GM scan tool and they weren't firing right. also have replaced the fuel pressure regulator, plugs wires have checked all the coil packs. The other thing the truck has done since i have owned it when the motor is warm and you turn it off and run in to the store or something and come back out and go to restart it its hard to start like it takes two trys or its a long time turning over. so i dont know if this is related or not. I have 4 other of these same trucks have have never had as many problems as i have with this one truck. Any input or ideas would be great thank you.
  14. Hello everyone!! I have an 03 silverado 4.3 votec 134k miles I got a year ago and its my first Chevrolet. I have an issue with misfiring around 1200-1600 rpm (usually overdrive) and i cant figure out the issue. I replaced the fuel filter, ignition coils, cap and rotor, plugs, and wires. I get a cat below threshold code, misfire cylinder 6 or multi cylinder code. The truck runs rich, it has a black buildup on the exhaust tip. I'm thinking tps because it seems to occur when the throttle would be pressed when normally cruising down the road maintaining speed. The trans shifts funny at times also leading me to believe tps even more. I wanting to get your guys take on it. Thanks in advance.
  15. I'm getting really frustrated with my pickup right now. I have to continuously take my truck into the dealership with check engine lights. The first 2 times they replaced the spark plugs. The third time they replaced a spark plug wire. The forth time they replaced another spark plug. The fifth time, they replaced two spark plugs and the valve cover on the drivers side. Now for the sixth time, they think putting in new pistons will fix the issue. Between the 5th and 6th time we are talking about 3 days. Last Thursday was the fifth time I was there and after I left the dealership, it was running great. Then on Sunday, I went to the store and when I left, I started up my truck and it started miss firing again. The dealership told me this morning that it was a random miss fire code. On the 5th time it happened, I drove the interstate for a good 45 miles and the miss fire cleared up on the way. On my way home from the dealership today, ran it pretty hard hitting 4k RPM between shifting, by the time I got home, it stopped miss firing. I am sitting here wondering if anyone else has had this issue. I am also wondering if the new pistons will fix the issue or if it is something else like a coil pack or something else.
  16. Truck is a 99 GMC Sierra 2500 extended cab 6.0L rear wheel drive about a year old with me and has about 260,000 Mods: true dual straight pipe with cats New ac delco spark plugs gapped at 0.062 MSD street fire spark plugs at 8 mm Any how one day was cruising and got a soda and started it up and noticed it was running on 3-6 cylinders pumped the gas a bit and all 8 came back coil packs are all sparking to the wire and all the connectors are delivering power 12v Need help with this ASAP next parts to replace will be performance coil packs then the injectors codes where p0300-random misfire detected P0102-maf sensor circuit low frequency P0332-knock sensor 2 circuit low input (bank2) x2 Autozone code summary says replace all valve springs and bad valve springs will cause popping and misfire but it misfires when I start it and put it in gear and only for a minute or so until I hammer down and get all 8 back running this is a very dangerous problem for me since it's my only vehicle and I have 2 children
  17. I am at my wits end. I own a 1997 C1500 Silverado extended cab and I have just rolled past 210k miles. I wish to keep the truck since I cannot find the money to buy a new one so I have been repairing and replacing as necessary, which brings me to my issue. I have owned the truck for 3 years and bought it at 160k miles and at the time it had some issues with it in the engine as it didn't idle just right and it choked up on hard acceleration so I replaced all the usual and got my power back but the truck always had a bit of a stumble that never went away. I replaced nearly every part that deals with ignition and timing and got to the point this January that I had enough money to pay someone to rebuild an engine for me and pulled the original engine and dropped in the new one (rebuilt). now the fun part, the stumble issue showed up in the new engine as well. I have paid two different shops to diagnose and bother cannot find the issue in why it is misfire. The kicker, is all the misfires occur in just the front of the engine in cylinder 3 (the worst) and 2 and 4. The other cylinders do not misfire and the miss is visible at idle and can be felt at any throttle while driving. The parts from the old engine were transferred to the new engine normally I would have assumed the issue was in the spider injector but it passed leak down test flawlessly. One more issue is it would seem that the computer is trying to cut fuel and the truck is running slightly lean. I am currently considering that even though the EGR test passes it may be possible that there is something wrong with it opening too far and messing with the front cylinders. Any assistance anyone who has an idea would be greatly appreciated. Thanks in advance
  18. Hey guys. Im new to to this forum. I will try my best to describe my situation as accurately as possible. Thanks in advance for your help! About 2 months ago i was driving home from work in my 2008 chevy silverado 1500 6L v8 when i started to hear a slight knocking sound coming from the engine about once every 20 times i tried to accelerate. I didnt think much of the sound until about 3 days later when i was driving and all of a sudden it started running really rough. Rough idle, poor acceleration amd lots of vibration commimg from the engine. So within the next day i purchased a obdii scanner and scanned the flashing engine light. The p0307 code popped up. Cylinder 7 misfire. From what i had heard this problem was usully easy to fix. So i went ahead and started changing things. I changed the coil pack, spark plug and injector for that cylinder. Nothing changed. So i did a compression test on the cylinder and it was reading between 0 and 30psi. That scared me a bit. So i took it to gm and after and inspection they told me i had a cylinder 7 misfire and to tell anything further they would have to take the engine appart. So thwre went $100 for nothing. So next i took off the cylinder head to see what was up. The cylinder itself looked ok, no damage. The piston was ok the one exhaust valve was black with carbon build up. So i decided to take the head to a machine shop to get it resurfaced and get a valve job done. He ended up replacing one of the valve guides but it wasnt the 7th cylinder one. So we put the head back on. Brand new gaskets and head bolts and everything. Got her back together started her up and same problem but it was as bad now. Weird that the problem got better but wasnt solved. We then checked the compression again and it was at a steady 120psi. Now i was confused as to what it could be. I checked the o2 sensors and they looked clean. There was no rotten egg smell comming from the exhaust so i assumed the cats were fine. Then i started playing around under the hood while it was running. I unplugged the wire from the map sensor and it started running close to normal. Weird. So i swapped the old map sensor out with a new one but no fix. I honestly dont know what it could be. Something to do with the computer im guessing. Maybe the pcm board? I heard these engines have problems with afm lifters but not sure what to think about that. My afm isnt working. It stays on 8 cyl all the time. Also command start doesnt work anymore. Sorry for the novel but im kinda desperate for help. Thanks again
  19. Hello all, I have an 04 Sierra 1500 with a 5.3. The other day I dropped the front pipe to replace the gasket between the drivers side manifold and the pipe. Before this, the truck ran well, no misfires except for the occasional P0300 that they're so famous for. After reinstalling the front pipe, the truck has started to misfire something awful. It has no power, and there seems to be an extremely excessive amount of liquid (not sure it's water) coming out of the tail pipe. I checked all the ignition wires to make sure I didn't pull any off, and they're all connected. I had scanned the truck, and came up with the same P0300 Random/Multiple cylinder misfire. My next thought was that I had damaged either the O2 sensor in front of the converter or the sensor harness, but I was told that the O2 sensor would not cause a misfire. I don't believe in coincidences, but I can't think of anything else that it might be. I've replaced both the driver and passenger side exhaust manifolds and installed a dynomax cat back within the past 5k miles, and before now have not had an issue. I was hoping to bounce this off of you guys and see if you had any thoughts.
  20. Hey guys, new here and frustrated... I own a 2004 Yukon XL 4x4 2500 6.0l 210k my issues consist of a slew of codes and terrible towing power with moderate fuel mileage. Here's my codes P0446, P0452, P1516, P0300 Those are my current codes, now the problems in having is sluggish pulling power under normal driving conditon with no load seems to run fine but just seems the 6.0l should have much more than she does. Under a 10k load she struggles, big time. Higher rpm over 3k. She clanks she sputters she pings and doesn't shift until throttle is released. rough idle at random times. 14mpg consistently I had the dreaded "engine power loss" but I pulled throttle body cleaned the crap out of it and replaced a broken ground wire from hood to firewall don't know which one fixed it but I have yet to have that issue pop back up since. But now it is this issue. I need assistance asap I use this truck to pull on a daily basis and it's so frusturating being the slow person rolling up a slight incline with a trailer Thank you all in advance for any advice, any input is appreciated I am not familiar with the 6.0 nor the entire vortec system.
  21. Im no mechanic to begin but i have done plenty of research and done enough service on my vehicle to know a little something. I have also had a certified mechanic of 40 years under the hood with me today and he left stumped as well. I need help from anyone who has any suggestions!!! I really am trying to avoid taking it to the dealership, that only creates more issues in my opinion. The people in the service department wont give any information just tell me to bring it in and pay a shit load to have them do it and i cant afford unnecessary repairs. with that said this is whats going on and the process in which i have gone with. I have an 09 silverado 1500 5.3L V8 325 flex fuel with 102,xxx miles on it. I have been getting codes for some time now for a misfire on cylinder 8 (P0308). starting with the obvious i replaced the spark plug but it didnt fix the misfire, the idle is also very rough. When the truck is idling is has a quiver and a shake obviously from the one cylinder not working properly. I occasionally get an EVAP code but thats only sometimes. Having the issue resolved down to that one cylinder i went about replacing the spark plugs twice, the spark plug wires, swapped coil packs, fuel injector, as well as the air filter. i tested all wires and hoses for issues and nothing. I unplugged the mass airflow sensor and thats not it either. When i start the truck i can hear a faint pinging sound underneath the passager front wheel well that sounds like a pain in my ass. The noise kind of sounds like the piston is hitting the valve. I just added some seafoam to the gas tank and im about to drive it around and get it circulated as well as run a compression test in the morning. If anyone has a similar issue i would love to hear about your experience and what helped you. Today i spent hours out there in the hot f-ing sun taking off the fuel rail, throttle body and intake basically the whole top of the engine to remove the tip to one of the fuel injectors that fell down in there before it caused major problems. How it got stuck in there im not sure not like those things just fall off, after removing the fuel rail i noticed that the tip was gone and couldnt be seen and i wasnt comfortable just leaving it like that so after breaking it down i found the 2 pieces sitting right on top of the closed valve. Now i bought this truck preowned with 85,000 miles on it and it wasnt long before i got this issue. The mechanic i have helpin me is stumped, he cant think of anything else that would cause a misfire on that one cylinder alone. the misfire is not random its always on cylinder 8. I have the truck covered under factory warranty for another 6,000 miles and i will take it in if compression is low in the morning and extensive repairs are needed on the engine but if its something i can fix for a decent price and my own hands i would rather. i dont trust shops all they do is try to create more issues and make you believe you need more work than necessary, I really dont want to hear all that bullshit. i havent checked everything i wanted to check yet but this is my list, i figured i would get a post going to see which are most suggested to test first leaky head gasket bad o2 sensor cam shaft sensor DME or ECU intake manifold gasket leak Idle control valve throttle position sensor fuel pump cam lobe cam lifters pressure regulator mass airflow sensor I will test until i find the issue for anything i am able and after that if i havent found it i guess i have to take it to the dealership. anybody anything????
  22. I installed the upgrade fuel injection spider in my truck. I did full tune up cap rotor plugs wires etc. And plenum vacuum sensor. I pulled and cleand the egr valve.I ordered a knock sensor will be in tomorrow. I still have the same misfire from 1500rpm til like 2200rpm.I guess I'm going to change all the o2 sensors. Also the cats and cam gear. Anthing else ? Thanks for your help..if anyone can.
  23. A little background: Im learning as i go here so bear with me. My 5.3 Silverado (has 195000 miles on it but very well maintained until the last couple years I got somewhat lazy about it). Over the course of that time I stated losing some balls on the low end and hearing a faint fluttering noise coming from behind drivers side dash when accelerating. It was annoying but reliable so I didn't think much of it.. and boy it's thirsty for oil. I never find leaks beneath my truck and I would get an oil change every other month as well as adding a quart in between changes. I have shorty headers on it and no cats and 3 inch pipes (wish I stayed with 2 1/4). Heres where I'm at: its running rough at idle and throwing PO300 codes. Misfires were occurring on all cylinders but mostly on two of them (cylinders 7 and 8 misfires over 1000 times over the course of 100 miles, the others arent misfiring nearly as much). I found this out after taking it to a shop after it randomly overheated and shut off a couple of days ago. The coolant looks like my baby's diaper and was a little low but no obvious leaks. They did pressure test, sniff head and checked for leaks, but found nothing. I feel stupid to admit but I've had this truck 3 years now aND I didn't know you needed to change out the coolant.(I plan to get it flushed out when I can). I will get it compression tested today and I will probably do a tune up on it just to be sure (replace at least plugs/wires, fuel and air filter, etc.) In the past year or two it seemed to burn a lot of oil, but this trick always did and ran fine. But now im getting what i think is oil coming out of the tailpipes and little white puffs of smoke (Sometimes at idle but almost always when accelerating.) I guess the elephant in the room that I'm trying to ignore (or at least put off) is an issue with a burnt valve or leaky head gasket. It seems like I have to play the game of tear the engine down or fix everything until it's better. Hopefully that wasn't confusing, but I can clarify if need be and the compression test I'll get done today will obviously help out. Thanks for any help.
  24. 2000 GMC Jimmy 4.3 Vortec 4WD ~215,xxx Engine starts, runs/revs in park but will stumble and miss off idle in drive. It wont stumble all the time though, sometimes it will run perfectly fine. Occasionally while driving in overdrive the engine will lose power, throttle does nothing, and drop to idle and begin stumbling and backfiring. After this happens if you let it sit for a few minutes it will start and run fine. Also this loss of power only occurs in overdrive, if I drive around in 3rd it runs fine. Fuel pump was replaced ~3 years ago Fuel filter ~3 months ago IM gaskets ~5 months ago (due to a coolant leak) Radiator ~8 months ago (cracked) Had codes pulled p0101, p0151, p0717, p0174 Anything you guys have would be great! Thanks!
  25. Well at 47,000 miles it happened. I cant find much for updated info on this subject so I started an account and thought I would ask. It started with the engine misfire. Brought to dealer and they replaced the plugs and added a new valve cover and oil diverter somthing. Im not much of a gear head so bear with me. From my reading I know this has something to do with the AFM in these engines, and my problem is just the beginning of a series of steps leading to piston and lifter replacement. Has GM made any steps to slove this problem? My dealer said my fix today was covered under powertain warranty. And there was a Bulletin for this fix. I then asked them about excessive oil usage associated with this and said this fix they did to my truck today solved it. Am I getting the runaround here? Im allready thinking I need to get rid of this truck before the powertrain warranty is done. Can anyone tell me if the AFM and excessive oil usage is still a problem? Thanks
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