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please help i can not find miss

Discussion in 'Chevy Trucks' started by mike s 88, Sep 30, 2003.

  1. mike s 88

    mike s 88 Junior Member
    Messages: 21

    hi, i have a 88 chevy 2500 with a fresh 350 in it. it has developed a strange miss under a load. i have changed plugs, wires, and the cap and rotor. i cant tell if its a fuel problem or just what it may be. any advice would be appreciated. thank you, mike
     
  2. snowjoker

    snowjoker Senior Member
    Messages: 283

    Is the timing correct? Or how about the fuel filter?
     
  3. wyldman

    wyldman Member
    Messages: 3,265

    Have you had it checked for codes ? Could be a bad fuel pump or plugged filter.I'd load it up and make it miss and then add a little propane down the throttle body.If it stops,then it's lean,like a pump or plugged filter.

    You can also use a timing light on the coil wire and flash it at the bottom of the injectors in the throttle body.The pattern should be nice,conical and smooth,with no dripping fuel.
     
  4. mike s 88

    mike s 88 Junior Member
    Messages: 21

    i think the timing is alright. do you know how to check for codes? i heard you can use a paper clip somehow? i will try the propane also. thank you. mike by the way it is much worse when the engine is cold.
     
  5. wyldman

    wyldman Member
    Messages: 3,265

    You have to jumper the two pins in the ALDL connector (key on)under the dash.The check engine\service engine soon light will now flash the codes.

    If it's worse cold,then it's probably a lean miss.Check the fuel pressure to verify the pump and filter are good.
     
  6. Crazy_Eddie

    Crazy_Eddie Member
    Messages: 38

    [​IMG]

    Use a paper clip to short A to B..
     
  7. Crazy_Eddie

    Crazy_Eddie Member
    Messages: 38

    Let me try to post this pick again....

    Didn't work... You can click on this link to ID the different pins..

    [​IMG]
     
  8. mike s 88

    mike s 88 Junior Member
    Messages: 21

    thanks for all of your help! two more dumb questions.. how do i know what the code is and would a leak in the intake gasket cause the chug it has? thanks again, mike
     
  9. wyldman

    wyldman Member
    Messages: 3,265

    Post the codes here,and I'lltell you what they mean,and how to diagnose them.

    An intake leak would only cause your miss if it's leaking through one cylinder at the head.The most common intake leaks are the throttle body base gasket,and that usually causes a very high idle.
     
  10. mike s 88

    mike s 88 Junior Member
    Messages: 21

    okay heres what i think the codes are 12 22 32 thats what it blinked out if you think i read it wrong please let me know. also while inspecting spark plugs one was kinda purple? thanks mike
     
  11. wyldman

    wyldman Member
    Messages: 3,265

    The code 12 is normal,it's always there.Don't quote me on these as I'm not at the shop with my manuals,but i'm pretty sure the code 22 is for the TP sensor,and the 32 is EGR related.

    I pull out the code book tommorow morning,and I'll post the correct definitions,as well as some further diagnostics.
     
  12. wyldman

    wyldman Member
    Messages: 3,265

    I've never seen a purple spark plug.Maybe that is your miss ? What plug gap are you running ?
     
  13. Crazy_Eddie

    Crazy_Eddie Member
    Messages: 38

    As usual Chis is on the money....

    According to Chilton's

    Code 22: Throttle Position Sensor
    Probable cause: A shorted to ground or open sisinal circuit will set code in 3 seconds.

    Code 32: EGR
    Probable cause: Vacuum switch shorted to ground or start up
    OR
    Switch not closed after the ECM/PCM commanded the EGR for a specified period of time
    OR
    EGR soleniod circuit open for a specified period of time.

    Don't ask me what it means... my expertise end with the paper clip thing..:)
     
  14. wyldman

    wyldman Member
    Messages: 3,265

    Code 22 is the TP (signal voltage low).Disconnect the TP sensor,and use a small jumper to short the grey and dark blue wires together at the TP sensor connector.Start truck for 10-15 secs,and you should get a check engine light.Pull the codes again,and if you get a code 21,replace the TP sensor.It probably is just a bas TP,but you should do the test anyways to verify the harness and ECM.

    Code 32 is EGR system failure.Need to know the GVWR to properly diagnose this code.They have two different EGR systems on these trucks.Either way,the code is set when the ECM commands EGR,and does not see a corresponding decrease in integrator counts (fuel trim),so it sets a code.It's usually a disconnected or misrouted vacuum line,or a bad EGR valve.
     
  15. mike s 88

    mike s 88 Junior Member
    Messages: 21

    thanks for all of your help.i do not have an egr on this engine. i am leaning towards the intake gasket. it only shows the check engine light once in a while. if i spray starting fluid on the intake the idle picks up.?? thanks again, mike
     
  16. wyldman

    wyldman Member
    Messages: 3,265

    While it usually won't cause a miss,just double check the throttle body base gasket.They are cheap,like $7.00,and take about 15 mins to replace.A lot cheaper and easier than an intake gasket.

    Spray some carb cleaner,or use propane around the base of the throttle body to see if it's leaking.
     
  17. mike s 88

    mike s 88 Junior Member
    Messages: 21

    thanks for all of your advice. can i just bring it to your house? i will keep you posted on what it is. boy this truck is killing me! thanks again, mike
     
  18. wyldman

    wyldman Member
    Messages: 3,265

    If you don't mind the drive up here,I'll fix it up for ya.Must bring coffee if you come though. :D
     
  19. mike s 88

    mike s 88 Junior Member
    Messages: 21

    here we go, i changed the spark plugs and the intake manifold gasket, i also changed the throttle body gasket. it still has a small miss but now it over heats real fast. could the gasket be covering up water jets? thanks, mike
     
  20. wyldman

    wyldman Member
    Messages: 3,265

    Did you use the right gaskets ? Were the coolant passages open at the front of each head on the gaskets ?

    Check the timing too.Should be 0 degrees with timing connector disconnected.If it's ******** it will overheat.