So I don't know anything about cars. But my truck has been having a few problems. It starts up fine and then the idle is really weird, the RPM's surge. The motor keeps bogging down and when you try to accelerate it sputters. The acceleration is cutting out. We've recently replaced the exhaust manifold (the old one had a bunch of holes) and the O2 sensor.

What could be wrong with my truck?

Please help!!!

  • Can you provide make/model/year of the vehicle? Dec 31, 2015 at 16:00
  • Are you getting a CEL (check engine light) coming on? You can get a free check for the code(s) at most auto parts stores. Dec 31, 2015 at 16:56
  • Chevy s10 1988 2.5 liter
    – user13991
    Dec 31, 2015 at 19:04

2 Answers 2


One possibility is an split hose causing an unmetered air leak. This is an cheap fix to look out for before spending money on expensive components. Check the crank case ventilation hoses and the main intake hoses.

  • 2
    check ALL of the vac lines also. If the vac line to the MAP sensor has a leak, it can cause major fueling issues (depending on the make/model/year).
    – rpmerf
    Dec 31, 2015 at 18:06

Since you replaced the O2 sensor and exhaust manifold, your truck may need to relearn its fuel trims. Try resetting the computer by pulling the battery negative post terminal for about 1/2 hour. This will force the computer back to factor fuel trims and give it a chance to relearn what's going on now that it's not receiving bad information about the quality of the exhaust gasses.

If that doesn't help, the part of the engine which controls idle quality is called an Intake Air Control (IAC) valve. This part is hung off of the throttle body. It has a plunger which is strictly in or out, but allows the proper amount of air through when the throttle is closed to allow engine to idle at a normal idle speed. If the engine is surging upon startup and not settling down to the proper idle, a sticking IAC could be what the issue is. The IAC also assists with off idle acceleration, so this could doubly so be at issue.

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