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Starts fine, but won't stay running (help)

This is a discussion on Starts fine, but won't stay running (help) within the General Help forums, part of the LSx Technical Help Section category; Car has been running great for some time. I recently got an SES, took it to Autozone and they said ...

  1. #1
    scheier
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    Starts fine, but won't stay running (help)

    Car has been running great for some time. I recently got an SES, took it to Autozone and they said the code was the cats going bad (bank #2). This was about a week ago. Car has about 80K, but motor only has 30K.

    Maybe unrelated, but worth mentioning. On two occassions over the last 4 days I turned the key, but got nothing. Next turn (both occassions) it started fine.

    Yesterday morning, I start the car up to go to work. Idle is rough. I keep it running for about a minute. Still no change. I pick up the RPM and get smoke out the back. Blue, white or black? Not sure. I think it was a grey smoke, girlfriend behind the car swears it was black. I tried backing out of the drive way to see how it would perform in gear and it is difficult to keep running at all that way.

    Battery terminal is clean and tight. Just replaced plugs and wires about 8 mohnths ago and all are tight. I'm sure there are new codes, but I can't keep it running enough to drive it to anywhere to check them. I'm thinking about dumping some fuel additives in case I got bad fuel (eg. water).

    Any thoughts or solutions?

  2. #2
    Member 98ls1blackbird's Avatar
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    I dont know if this will help or not, my LT1 Z-28 would start and run for a few seconds then quit. If I tried to keep it running with throttle it ran real rough and lots of smoke from being rich, then quit right away. Turned out the MAF sensor was bad. Good luck.

  3. #3
    SUPREME member-oderator oneBADDz's Avatar
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    Most likely either the Mass airlow sensor or the front O2s

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    CHASEM mpdcnva's Avatar
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    try this

    on mine the maf went bad, and stuck me far far away from home...not having a clue and i had all your clues and more i unpluged the maf sensor which sent the car into a fail safe mode. the car ran good and got me home....might try it.....

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    Senior Member SeVeReDiStOrTiOn's Avatar
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    Quote Originally Posted by z_driver1
    Most likely either the Mass airlow sensor or the front O2s
    I don't think it's the front o2's though...during open loop the o2's aren't used so it should run fine until warm. I'm with everyone else and say it's your MAF...but that's just a guess based off what you have told us.

  6. #6
    your parts guy!!! 1fastcamarosss11's Avatar
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    if you need one i got a brand new one in box. thanks jeremy

  7. #7
    your parts guy!!! 1fastcamarosss11's Avatar
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    trans am 00 ws6
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    have the same problem, don't know either. tried maf sensor not it. thanks jeremy

  8. #8
    scheier
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    So is it safe to unplug the sensor? What does that do to the computer and system in general?

    If I unpluged the sensor and the car stayed running, then I guess that I'd know that was the problem. I'd love to get the car to AutoZone before doing that so that I could see the codes to confirm it.

    I have an aftermarket Mass Air Flow. Does anyone have an idea of how long they are supposed to last?

  9. #9
    Single Malt rbob93's Avatar
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    Quote Originally Posted by scheier
    So is it safe to unplug the sensor? What does that do to the computer and system in general?

    If I unpluged the sensor and the car stayed running, then I guess that I'd know that was the problem. I'd love to get the car to AutoZone before doing that so that I could see the codes to confirm it.

    I have an aftermarket Mass Air Flow. Does anyone have an idea of how long they are supposed to last?
    Yes it's safe to unplug the MAF and run. (done it accidently before)
    It will run at a higher idle and shift differently (if automatic) but won't hurt your computer.
    As mentioned earlier, it's like a failsafe mode.

    How long do any electronic parts last? Untill they die, but I would think a MAF should last for the life of the car. Mine's @ 6 years & 112,000 miles now.
    Unplug it and fire it up, you'll have your answer.

  10. #10
    Senior Member SeVeReDiStOrTiOn's Avatar
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    Could also be a clogged cat....but try the maf first, you can usually bring it back for a refund if it doesn't look like you installed it.

  11. #11
    your parts guy!!! 1fastcamarosss11's Avatar
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    most place don't take that part back. they wouldn't take mine back be sure first. don't spend 30+ dollars without knowing. thanks jeremy

  12. #12
    scheier
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    I pulled the plug on the sensor and started it back up. Same exact performance (or lack there of). My brother has his factory MAF, so he is going to mail it to me so I can try it out.

    I thought it maybe the cats b/c of the code, but it ran great the day before right up until I turned it off. I can't see it going all bad over night.

    Any other thoughts?

  13. #13
    Member Flobeast385's Avatar
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    The best thing to do if the SES light is on or came on in the past is take to your local GM dealership and have it scanned. I know it will be fifty dollars but they can scan it with a "TECH 2" which is GMs life saver and tell you exactly what it is. I used to work at Advanced Auto Parts and the scanners they use suck. A lot of times cheap scanners will give, for example, an O2 sensor code but not show what made the O2 sensor send a false signal. Could be anything that regulates or measures air/fuel and it may save you money in the long run to know exactly what it is.

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    Any chance your running a K&N air filter? the fine oil buildup bungs up on the sensor and it cant accurately read the air flow. common problem. If you take it back be sure and mention your use of stock air filter only if they ask.

  15. #15
    scheier
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    I'll pull out the K&N filter tonight. I usually clean it every six months. It's probably been around a year since last one and I live in a new neighborhood full of construction dust. Thanks for that tip.

    Talked to another mechanic and his thought is that it would be a front O2 sensor (someone already said not viable because they don't kick in until car is warm, MAF (working this one, little brother sending me his stock MAF), or coolant sensor.

    On coolant sensor, I think I located it, just in front of first cylinder, drivers side, plug with two wires coming out of it. Not sure of expense, but to change out, I'm guessing this is just clipping the wires and splicing in. Anyone else ever hear about this or agree with this possibility?

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    Senior Member SeVeReDiStOrTiOn's Avatar
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    Quote Originally Posted by scheier
    I'll pull out the K&N filter tonight. I usually clean it every six months. It's probably been around a year since last one and I live in a new neighborhood full of construction dust. Thanks for that tip.

    Talked to another mechanic and his thought is that it would be a front O2 sensor (someone already said not viable because they don't kick in until car is warm, MAF (working this one, little brother sending me his stock MAF), or coolant sensor.

    On coolant sensor, I think I located it, just in front of first cylinder, drivers side, plug with two wires coming out of it. Not sure of expense, but to change out, I'm guessing this is just clipping the wires and splicing in. Anyone else ever hear about this or agree with this possibility?
    Try cleaning the MAF filaments with electrical cleaner also...like the guy above me said...could have oil on them from your k&n...have you re-oiled your filter lately?

    As for the coolant sensor...yes it's on the driver side head. There's no need to cut the wires....the end of the sensor plugs into the wiring harness. Coolant will come out when you take the sensor out...use thread sealer also.

  17. #17
    scheier
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    I reoiled the K&N last time I cleaned it. It's been a while. If what the proposed suggestion of unplugging the MAF sensor should have made a change in the performance so that it would at least stay running, I'm thinking I don't have a MAF issue. Best way to tell is the quick swap.

    Thread sealer. Noted. Thanks. I'll keep everyone posted on results and keep checking back for suggestions.

    Thanks all! The emails give direction, understanding and confidence.

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    member toneloc60's Avatar
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    Quote Originally Posted by 1fastcamarosss11
    have the same problem, don't know either. tried maf sensor not it. thanks jeremy
    possibly a stuck EGR.

  19. #19
    used and abused at wot ibanez7's Avatar
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    its definitely not the O2, I just installed LT with an ORY and ran mine without the O2s for alittle while and it was fine. Plus the o2 will richen the mixture when not operating or installed. THEY WILL NOT LEAN OUT YOUR CAR..

    When a car doesnt run its because of 4 things, spark, air, fuel and or pcm
    You say the spark is fine, I would assume your car is getting fuel, but maybe the mixtures are not proper due to poor sensor readings.

    check out these parts:

    MAF-dont touch the resistors but instead soak the unit in some cleaner(degreaser)
    I say this because oil based filters(k/n) can coat the resistors and cause the car to run like crap. GM will not cover that either!

    TPS- (throttle position sensor) its a simple potentiometer, but when it goes out you car can act all erractic. Check it with a multimeter/voltometer it should range smoothly from 3.7 to 4.6 V from idle to WOT.

    it could possibly be your IAC too, not opening and closing properly (doubt it though)

    For some reason it sounds like your car isnt asking for enough fuel and when under load that will kill your engine.

    One other thing and becarefull if this is it too, you could have a clogged cat, which will stop your engine from running since exhaust can not escape. If you allow your engine to idle too long, the header with the clogged cat will get extremely hot and could warp a head! To test the cats you would have to take your y-pipe off and feel for air pressure. Feeling the air movement behind the muffler will not display a clogged cat.

    just my .02 hope it helps and good luck!!

  20. #20
    Drive it like u stole it! newguy WS6's Avatar
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    Pull the valve covers and check the valve lash.. Then check your compression, and you might want tomake sure it has some gas...Just joking.. Because of all of the different responses above.. No offence to anyone.. just making a joke..

    Seriously I would Unplug the MAF and the TPS and see if it stops smoking/idling rough.. if it does narrow it down between the two.

    If that does not solve it it sounds like you have a bad cat.. i have had it happen before on previous cars that I have owned... Good excuse to buy some High flow units with some LT's

    Im betting on the Cat instead of the MAF and TPS

    Just my .02

    Steve

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