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98 chevy 2500 running lean

Discussion in 'Chevy Trucks' started by the new boss 92, Nov 25, 2011.

  1. the new boss 92

    the new boss 92 2000 Club Member
    Messages: 2,989

    i have a 89 2500 with the 5.7 and turbo 400 tranny. the other day i threw plugs in it cause it seemed to run a little choppey, bought some delco plugs and it smoothed the idle right out. but i noticed that the plugs, all of them were chocky white witch tells me its running lean. when its cold and i take off( about minuet of idiling) it starts running like it has a huge cam with no power. it will also do it once on occasion when its warm but only for about 15 seconds. im also getting a high idile when warm to but i checked for vaccumme leaks with either and no luck. im thinking it has to do with fuel delivery or something i dont know and i dont want to drive it and blow it up cause its runing lean. any help would be useful as im lost. :cry:


    my last truck did the same thing and i umpluged the o2 sensor and it didnt do it anymore so i replaced it and it fixed the problem. i tried the same thing here with no luck. im about to bang my head on the dash board cause im stumped and this really never happens.:realmad:
     
  2. the new boss 92

    the new boss 92 2000 Club Member
    Messages: 2,989

    might also add there is raw fuel splatter on the air cleaner cover!
     
  3. Holland

    Holland Senior Member
    Messages: 605

    I'm pretty good with tbi's but i need some more info..

    When the idle is high does it seem to hunt for an idle too?
    When your low on power is it all the time or will power pick back up if you change throttle position?
    When low on power does it run rough or just low on power?
     
  4. the new boss 92

    the new boss 92 2000 Club Member
    Messages: 2,989

    No idle stays the same through out the throttle positioning. No matter what the truck seems low on power compared to my last 5.7 it was a 92 same motor. It just breaks up real bad at low rpm when cold sometimes when warm. I just did a fuel pump but didn't have any luck as it was only pushing 5 lbs
     
  5. Holland

    Holland Senior Member
    Messages: 605

    Sounds like its time for a new set of injectors... Sounds like you checked for vaccum leaks already and if you did plugs im guessing you checked the cap and rotor out. The early caps were not vented and get corroded and gumed up real easy. Sometimes you get a miss other times a low power issue. So if you havent, double check the cap because i hate seeing someone throwing parts at anything to fix it. But it sounds more like injectors to me. If you've never done them its easy to do and i can help ya through it.

    Also... when you are ordering them, they might ask what lb injector you have. 55lb/hr for 350 engines, 65lb/hr for cop car 350 engines.

    You really only need the oe 55's. Just thought id tell ya in case they ask.

    A place to look for new ones might be www.injectors4u.com. They are priced really low through them. I personally havent bought from them but i wanted to pass on the link.

    Good luck!! Thumbs Up
     
  6. the new boss 92

    the new boss 92 2000 Club Member
    Messages: 2,989

    but wouldnt i have the miss all the time if the cap was bad?
     
  7. the new boss 92

    the new boss 92 2000 Club Member
    Messages: 2,989

    can an exsahust madifold leak cause it to run lean to this point?
     
  8. Holland

    Holland Senior Member
    Messages: 605

    yea... more so. im just saying i would double check it before you spring for a set of injectors... its free to check it!! When i swapped my 2.2 for a 5.7 tbi in my sonoma i fought all sorts of things. It would surprise you what can cause what.
    for example, i was having an idling issue where after it would warm up it would hunt for an idle, rpms would swing wildly and it would eventally die. Intermittent low power. Diagnosed a bad coolant temp sensor. NO CODES set either.
    I've also previously diagnosed bad cap rotor, injectors, tps etc etc So ive done it all. Each a separate problem. Never threw parts at it that it didnt need. The donor truck was an 89 2500 and had sat for quite some time before i pulled it. Only had 50k on the motor tho!

    But yea my first issue with it was low power and it turned out to be injectors, but one of our work trucks came in with the same issue and turned out to be a simple cap and rotor. Dont throw parts at it! please!!

    Heres the little sonoma..:mechanic:

    [​IMG]
     
  9. the new boss 92

    the new boss 92 2000 Club Member
    Messages: 2,989

    Yea I completely understand, I'm going to check some more tonight, do you know what the injectors are suppose to read on an ohm tester
     
  10. the new boss 92

    the new boss 92 2000 Club Member
    Messages: 2,989

    i found this on the cap and rotor, it did start tearing up the cap aswell. that cap was almost over tightened witch would cause the melting of the cap. could this be a lean causing problem?

    IMAG0048.jpg

    IMAG0049.jpg
     
  11. leolkfrm

    leolkfrm PlowSite.com Addict
    Messages: 1,419

    check the dizzy for a bad bushing.....seen it on early 90's
     
  12. the new boss 92

    the new boss 92 2000 Club Member
    Messages: 2,989

    yea, the distributor is pretty tight, less back anod forth than the last truck so im good there.
     
  13. the new boss 92

    the new boss 92 2000 Club Member
    Messages: 2,989

    ok i discovered a clogged fuel filter awsell, could really blow into it so i replaced that with the cap and rotor. its still breaking up at low r's how every i did get some power back already not 100%
     
  14. brianbrich1

    brianbrich1 PlowSite.com Addict
    Messages: 1,084

    Boss I had similar issues on my 97 chevy....no error codes but I was registering very high misfires on 2 cylnders....put all new injectors in and was good to go....
     
  15. Holland

    Holland Senior Member
    Messages: 605

    Sorry! i assumed you had already replaced the fuel filter... min res is 1.16 and max res is 1.36. but even if they are within spec they can still be bad. Remember, by ohming it your only verifying that the coil is good, not the injector as a whole.
     
  16. Mike N

    Mike N Senior Member
    Messages: 148

    Check the throttle body base gasket for a vacuum leak. Common on the TB engines.
     
  17. the new boss 92

    the new boss 92 2000 Club Member
    Messages: 2,989

    ill cheack the base gasket as thats the only one i didnt check, but everyrhing else i did for vaccume leaks. injectors are within spec maybe something is clogged in the tip? ill have to look at the throttle body itself a little better
     
  18. Holland

    Holland Senior Member
    Messages: 605

    since they ohm fine id take a look at the spray pattern, hook up a timing light and point it at the injector with the filter housing and spacer removed. hit the throttle a bit to give it more fuel and watch for an even pattern.
     
  19. the new boss 92

    the new boss 92 2000 Club Member
    Messages: 2,989

    ok i will do that, im going to dig up a timing light and see what happens.
     
  20. kashman

    kashman PlowSite.com Addict
    Messages: 1,070

    ohm test is not accurate you need 2 check it under load