Auto Repair - Roadshow forum

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Jeep Grand Cherokee Surging Idle

by TinMan68 / May 12, 2009 2:41 PM PDT

I have a 97 Grand Cherokee Limited 5.2L V8 that I bought with a blown engine. I changed the long block and used all accessories and sensors from the original engine. The new engine is in and it starts and runs but it won't idle. Instead it surges from 400 to 1500 RPMs and after a minute of this it stalls. I have replaced about everything and checked all I know how to. I scanned it and it shows no codes. I even took it to the Jeep Dealer and he can find nothing wrong or any out of spec sensors. Today I replaced the coil with a new one but as before nothing fixes it. I doubt its the PCM cause I removed the plugs and cleaned everything. When it runs I try tapping the PCM with a hammer to try to get some responce that maybe thats the problem but that doesn't help or do anything. I'm about at my wits end how to fix it. Once I get it in gear I can drive it and it doesn't stall. Sometimes it misses a little like a bad wire or plug which are all new. Anyone got any new ideas for me to try?

Thanks...

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Same problem
by RHANDLEY40 / August 12, 2010 12:03 PM PDT

We bought our Jeep from a used car lot that swore that the vehicle was a company car. After owning it for two months it started having major issues:transmission fluid was muck and we had it replaced and changed spark plugs and wires, battery ,fuel pump, pick up coil and rotor button, distributor, torque converter, All though after my husband changed the fuel pump the Jeep acted a lot better, but the mechanic told us that the code he saw was to change the crankshaft postion sensor and now it is so much worse. Surging while waiting for a light (acting like it wants to jump on them.)Help along with yours.

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RPM surge issue with 97 Jeep GC
by TRThomas111 / July 23, 2011 8:45 AM PDT

Did you ever fix the idle surging problem? I have a 97 Jeep GC that has been doing this for about 2 months. No codes. Replaced Throttle Body Position Sensor and Idle Air Control Valve. Still continues to swing on idle rpm as well as when driving.

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