Last post on Dec 05, 2013 at 8:40 PM
You are in the Chevrolet Silverado & GMC Sierra
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Chevrolet Silverado 1500, GMC Sierra 1500, Chevrolet Silverado 2500, GMC Sierra 2500, Chevrolet Silverado 3500, GMC Sierra 3500, Truck
#345 of 403 1997 GMC Z71, 5.7L Misfire/Backfire/Stumble
Jul 22, 2010 (6:23 pm)
I have an issue with '97 GMC with 225,000mi. It started a while ago with a P0300 that would occur intermittently. Then it started to get worse and the truck would shake, like it was cutting out. Currently it will start fine, warm up and then backfire when under light load at lower speed, high-speed cruising (mostly when being very light on the gas - kind or when you back out of it, then it will pop-pop-pop), or when I get off the gas when I reach speed. The truck performs pretty well when I get on it, relatively no hesitation and she has power.
I changed out the plugs, wires, cap, O2 sensors (upstream), transmission and converter, knock sensor, MAP, motor mounts, intake, exhaust, EGR valve, Evap Purge solenoid, and some more that I know i'm forgetting.
Bottom line - it's getting worse. I'm thinking it could be a PCM issue or another sensor that feeds the PCM values, because the truck will start and run fine until it warms up, after it goes "closed loop" the problems start kicking in. Another anomaly is that the truck will accelerate fine, that tells me the fuel pump is working well right?
I'm an active duty Marine and don't have a ton of money to throw at the issue. I decided to take it in the pants and brought it to the dealership here in DC. They kept it for nearly two weeks, never called me or returned my calls and so I went and got the truck back without any diagnosis. I can't afford to be without the vehicle for that long- or suck up the 120 an hour the dealer charges. Any help from you all is greatly appreciated. Thanks in advance for your response!
Semper Fidelis -
#346 of 403 Miss and bad exccelation
Jul 24, 2010 (5:10 am)
Just something to look at1994 silverado dies when put in gear and push the accelerator. Otherwise runs fine, it is a 5.7L vortec . Have changed almost everything (complete tuneup} plus the throttle possession sensor. The funny thing is that is the code it is reading. I have put 2 new ones on it, checked all the wiring and plugs to it. I have one person telling me it could be the MAS or the pick up coil. Any ideas?
WELL, we got it! Who knew.. It was the engine temperature sensor! It was failing so it was telling the throttle positioning sensor that the motor was cold so it kept dumping allot if fuel. So when the gas was pushed it flooded it and it would die! Problem solved!!
6 days ago
#347 of 403 Re: 1997 GMC Z71, 5.7L Misfire/Backfire/Stumble [nansenhome]
Jul 29, 2010 (8:28 am)
I would suggest you find a repair shop that has a good scanning tool, like a snapon. They will be able to tell you which cylinders are misfiring. The code should tell you but a P0300 is random misfire. I had a similar problem and had to replace the PCM. Turned out the connections for the fuel injectors were firing at the wrong time. The terminals were right next to one another. If your Check Engine light is flashing you are doing damage to your converters. Don't drive any more than you have to.
#348 of 403 Re: 1997 GMC Z71, 5.7L Misfire/Backfire/Stumble [wmaz]
Jul 30, 2010 (2:29 pm)
Thanks wmaz, The Check Engine light hasn't came on in a long time. Normally it will vibrate and then the light will come on without flashing. I'm looking into getting a new PCU from a salvage yard. Crossing my fingers it helps. Thanks again.
#349 of 403 2001 chevy silverado 1500..4.8L v8 vortec...rough idle
Aug 09, 2010 (12:19 pm)
hi all...guess ill start from3 days ago..3 days ago, while driving to work, truck spitted and sputtered then quit. revved it for about 15 min..all was fine..after driving 6 more minutes down the road does the same thing, but does not crank back up..i have it pulled to my home.put the diagnostic on it and got codes po171 & po174..replaced the bank 2 /sensor 2 o2 sensor and fuel filter. cranks right up and runs. now idling rough and wanting to stall out.check..ran diagnostic again over 10 times over last 2 days and getting 0 codes, but still really cannot drive it until the rough idiling and the wanting to stall issue is fixed....any thoughts or suggestions?
#351 of 403 2006 chevy silerado 1500 4.3 misfire
Aug 12, 2010 (5:52 pm)
diagnostic test shows misfire on 2,4,& 6 changed plugs wires, rotor ,and cap running worse than when i brought it in it idles rough boggs down revs between 2&3 and barely moves removed three of the plugs that i just replaced and they were black pistons sound off like they r goin to shoot through the block mechanic spent eight hours on it and has been stumped he smelled the exhaust and says it smells like its dumping fouled gas what ever that means did it by bad gas did somebody dump something in my tank or is there a different solution
#352 of 403 Re: 01 Silverado low idle & dim lights [fatboyntroy]
Sep 13, 2010 (5:18 pm)
i have a 2000 chevy tahoe and a had the same problem just go to any auto parts and buy a throtle body cleaner remove your intake hose and spray it real good in your throtle body, and it will take care of the problem.
#353 of 403 Re: Ticking or light knocking on cold startup [08gmcsierra]
Oct 09, 2010 (1:52 pm)
Mine started when I changed to synthetic oil. Was my first oil change. They should extend our warranties on this engine.
#354 of 403 Lack of Power, almost like missing.... help
Oct 20, 2010 (3:20 pm)
I've got a '99 silverado 1500, and it runs very irradic. under very slow acceleration it's fine but if i get on it at all it stumbles and falls on its face. Also when cruising down the road it runs fine until I start going up hill, then it starts to stumble again until i hit the gas and kick it into another gear. This truck also wants to die when i shift from R to D. This is very aggravating... It seems like the cooler the temperature gets the better this thing runs.. any help would be greatly appreciated