Hi,
I have a 2000 Grand Cherokee Laredo w/ 4.7 V8. Sometimes when it is idiling in park the engine will surge. The tach starts rising and falling just below and just above 1,000 RPM. It doesn't do it all the time and restarting will usually stop it for a while. I took it to the dealer a few weeks ago and they said it was a dirty air filter. That didn't stop it so before I spend more $$ does anyone have suggestions? The Jeep has 68K miles.
Thanks for any help, Brandon
Sounds like symptoms of an idle air control (IAC) valve, but it's just a guess without testing it. Sometimes they just need a good cleaning. Maybe someone else can confirm this for you.
Chris
I couldn't disagree more with the misfire advice. If there were a misfire, engine computer would pick up on it and turn on the MIL. Engine idle speed is controlled by the IAC for large changes, and ignition timing for small, fine adjustments. Various inputs to the computer can cause it, including TPS and MAF as heavy hitters.
Don't diagnose it yourself, you will spend far more money than the $75 or whatever a good dealer shop will charge. In the hands of a good tech, this should be a pretty simple find and fix.
Jerry
Thanks for the advice!
I hade the spark plugs replaced about 1,000 miles ago so that can't be it. Where are the IAC and TCS located? I would like to take a look at them and try cleaning them if they aren't hard to get to.
-Brandon
Was that before or after the problem started? If before, it might just be that you got a bum plug...
You know, I always suspect the MRFWU (Most Recently F***ed With Unit)
-Fred W
It was doing it before the spark plug change. I wish it was the MRFWU plugs...then the dealer would hae to fix it =)
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