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Showing results for tags 'intermittent'.
Found 4 results
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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 -
Intermittent Door Lock Cycling, Chime Operation Wont stop, Rear Access Open and Battery Drain issues. Do you guys have any fix for this? I just change new battery and its still doing the same thing! here is a video of it -
Hi Everyone, So my truck has been at the dealership two times officially now. This 3rd time I had my friend look over it and he said the truck was within GM's specs. I don't know what GM's specs for vibration are but my vibration is in the mid 70mph range and excessively vibrates and then smooths out. This is a constant cycle throughout my commute. I am going to pull my driveshaft and take it to a shop that specializes in driveshafts. I know several people have had their driveshafts replaced under warranty and it did not correct the issue. My thoughts are if your truck originally came with an out of spec driveshaft chances are there is a whole stockroom somewhere in the Parts Department that has out of spec driveshafts mixed in with the ones without issue, hence the reason some people have no luck with driveshaft replacement. I really feel this could be one of the major issues behind all of this especially when there is documentation instructing the technicians at the dealerships to use hose clamps to balance the driveshaft. I'm sorry but I don't see hose clamps as a permanent correction to this issue. I will update this post when I get the results from the driveshaft inspection. Please feel free to share your thoughts and bounce ideas around. Collectively I believe we can find an aftermarket fix for this issue, it may not 100% resolve the issue but will at least save people from taking huge losses on trade in (if you did not go through a buyback/lemon/customer satisfaction program). (A lot of people are trading in / selling their trucks because of this issue) ***UPDATE 01-22-2016*** I contacted the Team at Precision Shaft Technologies (http://pstds.com/) in Clearwater FL and they were able to squeeze me in as a walk in. (Not there normal protocol. They were super friendly, informative, and VERY helpful!) I drove up there and pulled the driveshaft in their parking lot. They then put the driveshaft on a machine and it was a near perfect balance. They added one small shim to the U joint to get it perfect but I'm sad to say the vibration is still present and there was no change. However, when I returned home I put my truck up on jack stands and ran it up to the speed I had issues at (per GM's service docs) and there was NO vibration. I was extremely confused at this point. I dumbed it down and looked at the rear wheels while the truck was in drive (idle speed) on the jack stands (be sure to block your front wheels and disable traction control / StabiliTrak if you plan on doing this on your own). I noticed my left rear wheel has a slight flat spot it in so much so that it's extremely difficult to notice. I have not had a chance to swap a known acceptable wheel to the rear at this time. When I do I will update this post. A recap for a description of my vibration: -72-74 MPH there is a cyclic vibration. Roughly every 7-8 seconds the truck has a vibration and then the vibration disappears.
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I have a 2015 Silverado Crew Cab 4x4 with a base radio. Sometimes when I start the truck the radio does not play music correctly. All chimes work, the display works, and if I crank the volume to the max I can hear the sound very faintly in the rear speakers. Tried messing around with the fade/balance to see if it was a bad speaker, but it seems to be something wrong in the radio. It will intermittently blast sound, then cutout, then come back on again. I'm curios if anyone else has had this same issue.
