Question about 1990 Jeep Cherokee Limited

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Rough running Son and I put a rebuilt motor in a 90 cherokee we had bought not running. New Motor, replaced all sensors, MAP,Crank,Anti Knock, New Dist, Stepper etc. All replaced. It starts up and dies 3-4Xs then it will run. When you hit throttle it dies out. Oddly it runs better with MAP sensor not hooked up. I have tried two differnet MAP sensors thinking I was on to something. The EGR is also new ans working. Return fuel pressure is good. I tried new computer under glove box, that didn't work. Any ideas. 4.0 4X4 Thanks Scott

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  • plazmadogg Feb 15, 2009

    I have installed all factory hoses where they go. I have also added a couple extra ground wires from Battery to body and engine, and a separate dedicated ground to the computer. My son says we did not replace the O2 sensor, It looked ok to me when I looked at it.

  • plazmadogg Apr 02, 2009

    I checked the TPS with ohm meter, It works correctly. We positioned it correctly according to the manual and using a Snap On meter from a friend. 1990 only shows certain things, it does not produce error codes. The TPS is new and acts the same as the old one using an Ohm meter. We did not replace that air stepper motor right next to the TPS. I only get to work on this thing about every couple of weeks or so.,

  • Mike Butler
    Mike Butler May 11, 2010

    You've double checked all vacuum lines for proper routing?

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  • Jeep Master
  • 6,674 Answers

Try checking Throttle position sensor with an ohm meter. Remove connection, put probes on pins (hit & miss on which ones, but you'll find 2 that give you a reading that increases as throttle is opened) and read meter as you open throttle all the way open & all the way back slowly & smoothly. The reading should go smooth up & down, If it jumps, or doesn't move at all in some spots, it's probably faulty. Have you tried to get any fault codes yet?

Posted on Feb 16, 2009

  • Mike Butler
    Mike Butler Apr 02, 2009

    How does it run when warmed up, or is the symptoms you describe pretty well doing that all the time. That air stepper your talking about, AIS, or IAC, controls idle under load etc, to prevent stalling, That could be sticking, and although they say not to clean them, I'd be tempted to pull it off, & clean pintle & port with throttle body cleaner, and see if it makes any difference at all, even though it really shouldn't affect highway driving. Do you see any sensors in throttle body at all, such as Throttle body temperature sensor, or incoming air temperature sensor? I'll see if I can get a list of possible sensors used in that year, and see if we can narrow it down from there. The O2 sensor is always a possibility, even though it looks good. I'l get back to you. Timing in within specs?

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