Edmunds Answers

Voted Best Answer

  • avatar zaken1 02/28/11 9:05 pm PST

    I recommend having the mass airflow sensor and throttle body thoroughly cleaned; being sure to only use the recommended cleaners and following the cautions and procedures recommended by the manufacturer.

    I would also replace the spark plugs with NGK Iridium IX # 4344 (LTR5IX11). Some plug manufacturers recommend a .060" (1.5mm) plug gap on this motor; but NGK recommends a .044" (1.1mm) electrode gap. The wider gap used by some manufacturers may cause the intermittent misfiring you reported.

    If you live in a part of the country where gasoline without added ethanol is available; I highly recommend using it. Ethanol fuel additives will cause stalling and bogging. Posted below is a link to a nationwide list of stations which sell gas without ethanol in it.

    Source: http://pure-gas.org/

Answers

  • zaken1 02/28/11 9:05 pm PST

    I recommend having the mass airflow sensor and throttle body thoroughly cleaned; being sure to only use the recommended cleaners and following the cautions and procedures recommended by the manufacturer.

    I would also replace the spark plugs with NGK Iridium IX # 4344 (LTR5IX11). Some plug manufacturers recommend a .060" (1.5mm) plug gap on this motor; but NGK recommends a .044" (1.1mm) electrode gap. The wider gap used by some manufacturers may cause the intermittent misfiring you reported.

    If you live in a part of the country where gasoline without added ethanol is available; I highly recommend using it. Ethanol fuel additives will cause stalling and bogging. Posted below is a link to a nationwide list of stations which sell gas without ethanol in it.

    Source: http://pure-gas.org/

  • Stever@Edmunds 02/28/11 9:29 pm PST

    You can reply in this thread by clicking the Answer this Question button and that will help keep all the information in one spot. Thanks!

  • jv52988 02/28/11 9:42 pm PST

    If you dont mind me asking if it was the spark plugs wouldnt it cause the problem all the time? It doesnt happen all the time. Just some mornings.

  • zaken1 02/28/11 9:47 pm PST

    Not all misfiring caused by spark plugs happens consistently. It depends on the type of misfiring. What you describe sounds like the kind of misfiring caused when a spark plug insulator loads up with fuel and fouling deposits, and does not stay clean through a cold start and warm up cycle. Some brands and designs of plugs are much more vulnerable to this problem than other plug types, expecially in certain engines or under certain conditions. Some engines do not run as clean during start up as other supposedly identical engines do. The particular plug I recommended has greater resistance to this type of fouling than other plugs do.

    Source: 

  • jv52988 02/28/11 9:50 pm PST

    Thanks ill try that.

  • thomcat2 08/08/11 9:04 am PST

    I have the exact same problem on my 2004 Colorado 5 cly. Was you issue solved by changing the spark plugs? When I took mine to the shop (not dealer) they replaced the plugs and wires (not sure what plugs they used) and the problem was not solved.

  • daves21 07/29/12 11:01 pm PST

    I am having the same problems? Have you got any help or solutions that have solved this problem? Any advise welcome....thanks

  • drew71 08/20/12 11:56 pm PST

    I am having this issue right now on my personal vehicle. I am a master mechanic, but have worked on Volvos for most of that time, so Chevys are new to me. Let's start with what I know for sure, and we can piece together the rest.

    1) The cat isn't clogged.
    2) It's not the plugs, coils, wires, etc.
    3) It sure as heck isn't the tranny.
    4) It's not the MAF or MAP.

    Okay, now that that's out of the way, let me tell you what it is (if you and I are actually experienceing the same problem, of course).

    It's a lean condition. I'd be willing to wager that your vehicle overheats a little bit as well, especially when you really floor it and it's like this. This issue has something to do with fuel regulation.

    The fuel filter is a possibility, but unless you live in Botswana (in that case, congrats on learning to write English so well), then your fuel is and always has been clean, so that's not an issue.

    My guess is the fuel pump is going out, a regulator of some kind is bad, or the signal to send fuel isn't getting where it needs to be. That could be the cam or crank position sensor.

    Another possibility is that the intake has some kind of crack in it, but this is unlikely. I tested this on my vehicle by disconnecting the MAF sensor. Doing this throws the ECU into a closed-loop, sending a set amount of fuel into the engine based on RPMs alone, not air flow. This did nothing to resolve my issue, so that's out. You can also test this by spraying brake cleaner around the intake manifold and listening for RPM spikes as the cleaner enters any cracks in the manifold.

    Besides all this, I think the Colorado ECU is smart enough to compensate and eventually disregard faulty signals sent by bad sensors and leaks, given that the engine stalls. That tells me it's something mechanical and it cannot fix through software no matter what it tries, i.e., the fuel pump.

    Congrats, I think we found your problem.



    Source: I am an ASE Certified Master Automobile Technician

  • boomers_mom 08/28/12 3:09 pm PST

    Our truck stalled while driving, had it towed, the shop said it was the fuel pump, but then called back and said it had run out of gas! Turns out the gauge was defective. During all this, mechanic found that when he put gas in, it was hard to keep the pump handle from shutting off - discovered that our fuel vent solenoid was bad and we had gotten vapor locked.

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1. MrShift@Edmunds 80
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