Jeep Idling issues, please help!!!?

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Ok, so I have a 1992 Jeep Cherokee Xj 4.0L straight with a throttle body injector. It turns over and idles and runs pretty smoothly, but after about 20 seconds the power drops out and the RPMs fall to almost nothing. Sometimes it catches itself, but the it spikes really high, like 25 rpm then drops back to a normal idle of about 6-850 and repeats the process over. When it stalls on me, it spikes really hard when I turn it back over. Seems like its flooding, but would could cause this? I’ve heard a vacuum system leak might, but wouldn’t it cause immediate idle issues from the start? I cleaned the IAC valve. All my plugs and wires are brand new. As is the distributor cap and rotor. I’ve heard it could be my TPS or the MAP. Someone suggested a faulty O2 sensor. Someone thought my injectors might be gummed up. I’d rather get a better idea of what it is before I start dumping money into things that don’t need to be replaced. THANKS GUYS!!!

✅ Answers

? Best Answer

  • A bad throttle position sensor (TPS) would be my first guess. Followed by a bad idle air control (IAC) module. You really need to connect to an obd code reader to further investigate. 92 would be pre OBDII so the regular code readers commonly available probably won’t help. Some Chryslers allow you to do an emergency code check by inserting the key into the ignition, turning it on, then off, on then off, and then on. The check engine light will begin flashing a series of timed flashes with pauses in between. You can count these to find out what codes are pulled. Each code is a two digit code, so a (for example) 23 would be FLASH FLASH (pause) FLASH FLASH FLASH (long pause). It will never flash more than 9 times, so watch for those pauses!

    Check here for a list of codes- http://www.cherokeeforum.com/f2/jeep-com…

    These are generic Chrysler codes that should apply to most older OBD cars.
    This should help you track down your problem. I would bet you pull code 24 – Throttle position sensor over 4.96V. Best of Luck to you.

  • Did u check for any vacuum leaks? I sprayed carb cleaner on my vacuum hoses and if you hear a change in rpm after spraying a specific spot then that’s your vacuum leak. Be careful as carb cleaner is flammable and may combust on a hot engine. I’ve heard other people use wd-40 as well but I just stuck with the carb cleaner. Also check your ignition coil. I just replaced mine. But my jeep was misfiring a lot. Not sure if yours is doing the same.

    Source(s):
    Had to do it myself

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