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Chevy Silverado and GMC Sierra Gasoline Engine Problems



  • obyoneobyone Member Posts: 7,841
    That's more of a phrase that they use rather than actually rebooting.

    So they haven't changed the wiring harness?
  • bwanderseebwandersee Member Posts: 1
    i have the same problem and have replaced the plugs,dist cap, rotor, fuel filter, fuel pump, fuel pump regulator, and egr valve. does anyone know what to do now but send it down the road? the truck only has 70k.
  • seedsseeds Member Posts: 1
    send it down the road i have gone through this with 4.8 they say its binding in the valve guide after i spent a small fortune on it. dealer said to pull heads and clean . but they would not garranty this would fix my problem,they think money grows on trees.
  • jostiguinjostiguin Member Posts: 3
    Yeah that was the first thing they did
  • jason2500jason2500 Member Posts: 3
    Im not sure if you fixed your problem yet or not man Im new to the fourms. but i have the same truck and last year i done a complete flush on mine and was having the same problem, if you changed you water pump or anything to lose antifreeze then your probly airlocked. run your engine with the cover off the coolant bottle keeping an eye on the temp gauge this should work. let me know how it turned out
  • jon69jon69 Member Posts: 2
    I've got a 2000 with 4.8 and had this problem when I bought it with 130000miles. I had to clean the throttle body with carb cleaner every 6 months until I switched to synthetic oil. Coincidence????
  • buzzatbuzzat Member Posts: 3
    Truck starts up fine but the idle drops very low and goes back up continuosly until ithe idle drops and car stalls please help, ive already changed battery, plugs pickup coil, coil and spark wires and distributor cap
  • buzzatbuzzat Member Posts: 3
  • buzzatbuzzat Member Posts: 3
    I also used a code reader that gave me a code 54 indicating the fuel relay or egr ive since changed the fuel pump relay which cleared the code 54 but truck still stalls, i then changed the egr vacuume solenoid and egr valve, the truck runs better but the idle still drops low and back to regular continuously until it drops so low that it stalls even if i hold the revs up it still goes down and back up to where i had it, i have no idea what to try next o2 maybe??? PLEASE HELP!!!
  • obyoneobyone Member Posts: 7,841
    Have you changed the fuel filter? Can't remember off hand but does your truck have an idle air controller?
  • dmbaerodmbaero Member Posts: 5
    Greetings! Have a 1999 Sierra Z71 with 5.3L engine, last winter service engine light would come on when engine was started when very cold only. Check of codes showed P0171 and P0174 fuel system lean bank 1 & 2, after posting determined fuel pump pressure low, replace MAF, EGR valve, fuel pump, fuel filter, & fuel pressure regulator over course of several weeks attempting to fix . This improved problem but didn't completely go away. By time all of this had been done it warmed back up and no problems since. Since it has turned cold again recently, had service engine light come on when engine was cold and sometimes after this happens it will idle fine but surges in 15-40 mph range. At highway speeds it runs fine. Rechecked codes and found P0405 EGR sensor A circuit low. Truck has factory engine heater and when it is plugged in overnight problem doesn't occur, but when parked at work for entire day and then started cold it will trip. Suggestions on possible places to look to solve problem? Any help would be appreciated! Thanks!
  • Silverado_2003Silverado_2003 Member Posts: 1
    Hi Treedog,

    I just read your thread on the overheating and airlock issue with your truck. Although it's been several months since you resolved the issue I'm hoping that I can get some details on how you resolved the truck is having the exact same problem after changing a leaky water pump and old thermostat.


  • vettenjetvettenjet Member Posts: 1
    dmbaero, I have a 2000 GMC sierra with 5.3L and I am getting the same 0171 and 0174 lean b1 and b2 as well. just replaced all injectors. motor has 205,000 miles on it and still runs very well. A while back I did remove the MAF and clean it according to the spray can instructions but that did not help the SES codes either. Did you finally resolve what the problem was on your? Any help you might have would be greatly appreciated.
    Thanks, vettenjet
  • trinertriner Member Posts: 1
    I have a 1993 GMC Sierra. I parked in my driveway, shut it off, came back out in about 5 minutes and will not start. I changed the fuel pump relay. I have no voltage to the fuel pump fuse located on the firewall, and no voltage out of the relay. I don't think that I have the fuel pump/oil pressure switch on this model, but I do have the oil pressure sending unit. It doesn't have the wires that my schematic says it shold have, just the one output line. All fuses in the cab are good. Any ideas????
  • ss3ss3 Member Posts: 4
    Did you fix your problem with your Silverado overheating? If so, what did you do?
  • dmbaerodmbaero Member Posts: 5
    Greetings All! 5.3L 1999 GMC Sierra Z71 with 233,000 miles
    I have posted here a couple of times in the last year regarding ongoing problems with P0171 & P0174 bank 1 lean and bank 2 lean codes. After continually chasing the problem, recently while driving at 65 mph on interstate the vehicle lost power. The cruise control was on at the time and the light still showed it as engaged, engine was still running, but vehicle just was losing power, when accelerator was pressed down, nothing seemed to happen, if pressed to the floor, it would cough and act like it was backfiring. Pulled over and shut off, called someone to come pick me up which was going to take about 30 minutes. After the vehicle had set about 15 minutes, decided to retry, found it started up fine and ran fine at highway speeds for about 20-25 miles then problem reoccurred, no SES light and no codes. Shut down and let cool for 10-15 minutes and able to continue on for another 20-25 miles. It took about three legs like this to make it home, on last leg I had noticed while using monitor mode on scantool that when problem occurred a couple of the oxygen sensors went to 0.0, also found couple of oxygen sensor codes pending. Long story short, ended up replacing oxygen sensors after removal for troubleshooting due to threads galling on removal. Also replaced catalytic converter Y pipe for same reason. Seemed to fix problem, vehicle ran fine for 2 1/2 to 3 weeks. All of a sudden on way home from work, had same problem occur. Noticed this time on scantool monitor mode that when problem was happening that the fuel loop 1 and fuel loop 2 were showing open, so computer was not using oxygen sensors to adjust fuel. Presently going through all grounds on vehicle and cleaning, then going to check connections at PCM. My questions is if there is any procedure to test PCM other than having GM dealer go through troubleshooting chart with Tech II?
  • nmgmguy22nmgmguy22 Member Posts: 2
    I have an 04 Sierra with a really bad idle problem. Let me start out by explaining the first day of problems. I was heading out to school one morning and I had a bad misfire. I went to the local garage and they said it could be the ethonol in the gas and to treat the gas with Stabil Marine cause everyone is using it right now to cure their problems.

    That sunday I started to notice that the RPMs would drop down to around 500 where it never used to drop to. I decided to go to the dealer and see what they would fine after a a week cause the truck was still running rough and now low idle. The dealer found a bad O2 sensor on bank 1. They replaced that and it still didn't cure the low idle but stopped the hitching. They said replace the spark plugs if it dont clear up and so I did with the originals in the truck. Still no fix. I went down this past week and they said that my throttle body unit would have to be replaced. So I replaced that and still no fix. I also had the intake gasket checked thats good. They said the injectors were firing good. Both garages I have been to virtually cant find anything. I know personally it's not running normally.

    I am going broke and going nuts trying to figure out the problem. When I come to a stop the RPM goes way down to 400 then will go back up to around 500-550. I used to idle normal at 750-850. I am hoping someone out there can help me out or may have had that same problem. It also seems to take a while to shift in the hills and to make it shift I have to give the pedal more gas. I know eventually its gonna start stalling and what not.
  • stacks125stacks125 Member Posts: 6
    95 GMC_350_Z71_1/2 ton_130K miles. Truck would run but loss of power at low rpm's. If you gave it full throttle it would run great. If you held gas lightly in reverse it would go but then stall after you took you foot of the gas. Mechanic said computer was telling egr to stay open so he replaced the ecm and said it ran better. I got it back and it ran the same for me. Put new fuel pump, stem, lines and filter and that fixed about 80% of it. It now won't stall but runs rough at 500 to 1000 rpm's.(the rpm's like to jump up and down)
    I went back and the mechanic hooked it up again to his sensor and the new ecm also telling the egr to open a little. He unplugged the solienoid(wiring harness) to the egr and now it runs perfectly but that doesn't mean its fixed plus the ses light came on later. What I can't figure out or him is what is telling the computer to open the egr when it is not supposed to. I don' t think that there is a leak in the vacuum lines or egr is stuck open because then it would still not run good when we unplug the egr. But if I am wrong, please don't be afraid to tell, hit me with whatever you got.

    I appreciate the help Derek
  • stacks125stacks125 Member Posts: 6
  • obyoneobyone Member Posts: 7,841
    First clean your idle air controller and check your throttle position sensor.
  • nmgmguy22nmgmguy22 Member Posts: 2
    When I replaced the throttle body everything came as one unit. I also noticed the other day that it only begins to idle low once the truck had moved out of gear and is warmed up. When I first start it up it idles normally. I also looked at replacing the PCV valve but its built in. Anymore suggestions? Thanks
  • spalspal Member Posts: 1
    We are looking to buy a 2006 Sierra 1500...We tow about 2000 lbs. and need to know the difference between these 2 engines...Our favorite boat ramp is fairly steep and we don't want any problems with power...We also have a 4.3 V6 Safari van that lugs down a bit , pulling the boat out of this ramp...
    Is there a big difference between the 06 and 07 trucks? Should we wait and try for an 07 instead?
  • cjjonescjjones Member Posts: 2
  • cjjonescjjones Member Posts: 2
    I have a 2001 GMC 5.3 and the truck wants to start on its own.
    It will crank over with the ignition off. If you put it in gear it doesn't do it but in neutral and park it does.
    I have a command start that I totally removed and it still does it. So it is not hte command start.
    I have removed the starter completely and and the wire is live. So it is not the starter.
    I have replaced the starter and ignition relays and it continues to turn over.
    It doesn't do it all the time but it happened today when I was no where near the truck and burnt out the starter.
    Any ideas would be great.
  • jeffkalijeffkali Member Posts: 2
  • jeffkalijeffkali Member Posts: 2
    I degreased the engine on my 94 gmc sierra (350 4x4), and now my idle is high and the trans won't shift....some times at very high rpms. I'm assuming something is still wet, but it would be nice to know what.

    Please help, Jeff
  • mydogisalabmydogisalab Member Posts: 2
    I have had four ignition modules witin in the last two years. Three of these were within the last week. The shop claims it is a bad module, but three in a row? Does anyone have an idea on what else I can look for that is blowing up my module?

  • surrfurtomsurrfurtom Member Posts: 122
    This is probably a moot issue by now, but for future reference.

    I had a similar problem on my 2000 5.3 about 5 or so years ago. It would start with a rough idle and then either clear up or continue or get even worse. It seemed to me the engine was losing a cylinder. The check engine light would come after a while.

    The dealer spent a long time and multiple visits trying to fix this as it was intermittent and didn't act up at the dealer. Luckily it was under GMPP as they lots of time and threw parts at it and it was out of initial warranty. Once it finally misfired when in the shop they scoped it and determined one cylinder was misfiring. It even destroyed two cat converters because of the richness of the exhaust when it misfired. As I recollect it turned out to be the ECM that was bad and it was affecting only one cylinder. The codes set were always general misfire.
  • og_ninjaog_ninja Member Posts: 1
  • beverollbeveroll Member Posts: 2
    Did you ever figure out what the problem is - I am having the same problem with my 94 chev 1500. Have had the map sensor done, 02 sensor and EGR done and still not fixed - sounds like exactly the same as your problem - we are getting very frustrated. Any hints would be very helpful
  • jdspradjdsprad Member Posts: 6
    Does a website exist where I can enter my VIN, and bring up all of the vital info of my truck, similar to that found on a window sticker at the dealer? I recently purchased a 2004 GMC 2500 CREW (6.0L), and the seller did not have the original sticker, nor did he know what gear (rear-end), or transmission that the truck has. Did GM install more than one type of tranny in the gassers for that year? I got a heluva deal on the truck, so I am not real concerned, but still need to know exactly what I have here. Any help would be greatly appreciated. Thanks.
  • jdspradjdsprad Member Posts: 6
    Who has the better repair manual, and why? Thanks.
  • akjbmwakjbmw Member Posts: 231
    A more complete manual can be found at Helm Inc.
    It is the company that prints the user manuals for the dealer.

    Pricey, but you have to consider the accuracy and savings of doing it yourself.
  • jdspradjdsprad Member Posts: 6
    Thanks for the reply......I will check out the site.
  • txrednecktxredneck Member Posts: 8
  • txrednecktxredneck Member Posts: 8
  • jdspradjdsprad Member Posts: 6
    Typically, does the alternator get noisy right before it pukes; or just a sign of age. There is 80K miles on my original "Delphi" it about time?
  • dkizerdkizer Member Posts: 1
    I have trouble removing the wire boots off of the spark plugs on my '04 5.3L. Does anybody know a technique that would help?
  • dmbaerodmbaero Member Posts: 5

    In answer to your question, I seem to have finally fixed my problem. After several months of fighting numerous possibilities during which I have changed the MAF sensor, throttle position sensor, EGR valve, all four O2 sensors, catalytic converter, fuel pump module, fuel pressure regulator and fuel injectors; and also cleaned all grounds on the engine and frame, tried reseating the connector to the PCM. None of these seemed to fix it, at most it would go 3-4 weeks after some of these fixes before it would act up again. The last month or so it seemed to become very sensitive once the outside temperature was over about 90' F. I have an Auto Xray scantool and began tracking all the readings I could monitor and determined that it was not getting enough fuel. When it would lose power, what was happening was that the computer was sensing detonation from the anti-knock sensor and adjusting the timing to prevent this. I found that when it would act up, if I watched the timing on my scantool it would go from about 37' (normal) to 4' if I pressed down on the accelerator and back up to 37' when I released it. I was finally at the point that I thought it was the computer, so I wrote down all the codes, a list of all items I had replaced and when, and the trend monitoring I had done in the last several days and took it into the dealer with all this info. They started troubleshooting and found that the fuel pump was weak. I had checked the fuel pump at idle and it registered about 50-52 psi which is at the bottom of the limits, but the dealer did something I had not thought of doing. They attached the fuel pressure gauge to the fuel rail with a long enough hose that they could tape it to the windshield and watch it as they drove the truck. At idle it showed about 50 psi, under normal acceleration it would still show about 50 psi, but if you really accelerated hard the fuel pressure would drop to 10-15 psi. I modified my pressure gauge with a long hose and drove it so I could see this happening. The fuel pump module I installed was one of the first items I replaced and that had been about 1 1/2 year ago. After seeing on the pressure gauge what was going on I was skeptical that this would fix it, but it did need resolved before they could do anymore troubleshooting. So I purchased another fuel pump module. This time I bought a Delphi unit, the first unit was just what the local O'Reilly looked up, an Airtex unit. I had checked on warranty for the first pump which was only a year and had asked if the Airtex unit was the best and that is how I found out about the Delphi. Anyways, I installed the new fuel pump module on July 4th and drove the vehicle to work the next couple of days with the fuel pressure gauge taped to the windshield. The fuel pressure is at 52 psi at idle, runs around 56-58 psi during cruise and goes up to 60-62 psi when accelerating very hard. The truck has not acted up since and I have even pulled a fairly heavy trailer load and it worked fine. I had noticed when it was acting up that the short and long term fuel trim values on my scantool which indicate how the computer is adjusting the open intervals for the fuel injectors were running at 25% pegged for long term and would peg at 53.9% for short term which is when the vehicle would act up. I have monitored these values since the new fuel pump and they never get above 10% on either and most times run right around 0%. I would never have thought that the fuel pump would have fixed it but it seems to have worked. Hope this helps and saves on future headaches.
  • helpmetodayhelpmetoday Member Posts: 2
    I am having the same problems as.. mydogisalab.. 4.3L engine Z in a 1993 G-20 van. symptoms, stops like turning the switch off, will restart , sometimes have to wait ten-15 minutes. This stop and start, is totally random. replacing the module is a temporary solution, for about 500 miles and 30 or so starts. When it runs it performs perfectly.The Van has only 45,000 miles, this problem showed up about 2,000 miles back. any ideas? please.
  • mydogisalabmydogisalab Member Posts: 2
  • crown3crown3 Member Posts: 1
    220,000 miles, engine light is on and I've been told by few friends that it's likley the Oxygen Sensor, I've read several posts and notices that there may be more then one sensor.
    #1 Where can I find detailed instructions with diagrams hopefully, how to place one or more of these sensors, if I'm able to determine through the local parts store which on it is?
    #2 Is this a job that a basic do it yourself person can do?

    Thank you
  • kevin1970kevin1970 Member Posts: 4
    I was given a 2001 chevy silverado 2500 6.0l vortec. Its has 297,500 miles on it and runs very good, but however i have this tapping noise like everyone else have. But in my case, its at the start, during, and finish of my trip driving. My question is, "Will a 20/50 oil help or what would someone with experience suggest?" Thank-you in advance for any help.
  • davethecarnutdavethecarnut Member Posts: 248
    I would try those high mileage oil's constantly ticking when the engine is running? Maybe oil isn't getting up to the valvetrain.....
  • kevin1970kevin1970 Member Posts: 4
  • obyoneobyone Member Posts: 7,841
    There are 4 sensors. One before and after the catalytic converters. Since you're at 220K miles, I'd recommend changing all 4.

    It's easy to do but you need to buy a special socket.
  • kevin1970kevin1970 Member Posts: 4
    Thanks Dave, Ill try them additives....the oil pressure gauge is bouncing back and forth between 30 and 60 while i drive and it will literally go to zero (0) if i stay in idle/park and the message light will say check oil pressure and the truck will cut off. Think the oil pump is bad? Thanks.
  • kevin1970kevin1970 Member Posts: 4
    On the Chevy Silv., 2001 - 6.0l vortec, w/ 298k miles...the oil pressure gauge is bouncing back and forth between 30 and 60 while i drive and it will literally go to zero (0) if i stay in idle/park and the message light will say check oil pressure and the truck will cut off. Think the oil pump is bad; going bad; the lifter/s or valve/s is tapping sorta loud? Thanks in advance for any advice. Kevin
  • Duane99Duane99 Member Posts: 11
    Did you find out what caused this? Mine will start up and act like it is flooding or running rich, backfiring under the hood and have no power for about 1 or 2 minutes and then it is fine. It doesn't usually do it in the morning, but when I come out after work, it does it almost every time.
  • bassprobasspro Member Posts: 34
    I have a 6.2 Flex fuel 09 403HP. My question is does anyone know how the roller lifters are oiled in my engine?
    In the old days of hydraulic and solid lifters splash seemed to work in non Hi-Perf. motors. I have read on some forums that roller lifters and roller rockers need lube. It is said,in low rpm range, MODERN ENGINES do not splash as much oil as older motors and the needle bearings of modern motors need oiling at low RPM's (2000 to 3000RPMs) or might have wear and breakage issues.
    Does any one in this community know of or heard any or some or just a few 6.2 L 403 HP V8's having roller issues? Does anyone know specificly,does the 6.2 have mist,pressure or non needle bearing rollers?
    I run syn. oil and will be running Oil analysis so I assume I would know if the needle bearing are wearing it would show even though I am running a bypass system that has a 2 micron absolute filtering.
    Ideas and opinions would be appreciated.
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