Question about 1991 GMC S-15 Jimmy

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I took a intake off

Hi i need help. I took my intake off because gasket was leaking anti freeze. I repair the gasket put every thing back on.its not running right. I didn't mark the position of distributor so i bunt motor over till number one up and turn crank til mark on balance line up on 0 degrees put distributor in. start it not good the i read you have to unhook a wire from under dash then set timing. I did still not running right. i took egr vavle off it working i took iac off it had build up on it. So i took tbi off and clean it without taking complete a part. Put it back on it still not right it has a miss and seems to be runnin rich and it has a spark nock . and i time it with a timing light. Can you help. Todd

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  • 2 more comments 
  • todd_fleury Jan 02, 2009

    Thanks i will try the carb spray. I retime it about a dozen times i'm trying to fix it for awhile now. i know the plugs wires are on right. I took them of so many times and put new one on . I took spark plugs out this morning and there black it tells me that its rich . Why now and spark nocks. is the spark nock sensor or model going bad. It controls also the preformance of timing .Yes it run good until i took the intake off.

  • todd_fleury Jan 02, 2009

    thanks i'm business today i will try tomorrow thanks again.

  • todd_fleury Jan 04, 2009

    Hi Thanks for the help. I took the number one spark plug out and got it top dead center again and took out the distributor again reset the time and i had it one tooth off . Recrank it . It seems to run good so far. Thanks

  • todd_fleury Jan 06, 2009

    Thanks. Did you know you have to unplug a wire from under the dash to time it? On that model thats were it at other models are different.



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Check to make sure you have the firing order correct. If so, go ahead and remove each wire to isolate the misfiring cylinder. From what I can understand from your post, it seems that so far, you have done everything correctly. Did it run well before you did the gasket? Running rich can be a product of a vacuum leak as well. To find it, spray some carb cleaner around perimeter of manifold, and near any vacuum source. If idle changes, that's where the leak is! If its leaking from the new gasket, you might consider, loosening up the bolts and re-tightening them in a cross pattern, side to side, beginning at the center, working towards both ends. split the torque value and tighten twice: if value is 30lbs, do once at 15, the second time @20. I hope this helps.
Good luck

Posted on Jan 02, 2009

  • Richard Scordino Jan 02, 2009

    A vacuum leak can cause it to run rich because the O2 sensor sees the lean condition and the ecm tries to compensate for it by dumping more fuel in!Knock can (may be) happening again due to overcompensation... with more fuel, it may be increasing spark advance as well.

  • Richard Scordino Jan 04, 2009

    Yup...That's the disadvantage of attempting to diagnose without seeing or hearing what's going on at the other end. I was right about overcompensation, just didn't "see" that the dist was in wrong. I have to reasonably assume that you did it right the first time, and therefore have to try and bring your attention to the most common "odball" problems that arise.Next time you will put a timing light on it before you start driving yourself crazy. Good to hear that it's fixed!!!



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