High Idling '88 XJ

I have a question in regards to my '88 XJ. This morning when I drove it to work, it idled fine while in Park. This afternoon after lunch, I started my XJ up again, and this time it idled extremely high while in either Park or Neutral. Everything else seems fine while the Jeep is moving. The temp of the vehicle when moving is around 200 degrees which I believe is normal. Any ideas as to what it could be?

Thanks,

Marty

Vacuum hose off something.

Like the man said, most likely a vacuum leak. On that year model, the small hard line that runs down behind the battery and to the vacuum bottle behind the front bumper is the normal culprit. It breaks right next to the battery tray.

Tom,

I checked that line you were talking about and it seems to be ok. I did notice however, that there was a whistling sound while the engine was idling and it sounded like it was coming from the airbox area...

I'll check the TPS as well and see if that might be the culprit.

Thanks,

Marty

Check the small hard line from the MAP sensor to the back of the throttle body.

If it well out it will go into the bottom hole, the top hole is blocked off.

Common problem on '87/88 with the big electrical connector above the brake booster. While it is high idling, grab the connector and gently move the harness around. You should see a drop or even higher RPMs. Clean all connectors under the hood (with electrical contact cleaner/sealer) and rebend the prongs so they all make good contact. Usually makes the probs go away on Renix rigs.

I would bet a sixpack on it being vacuum related. See if you can borrow a vacuum gauge. The vacuum should be around 15 or more at an idle.

Just an update on my idling issue.....

This past weekend I went ahead and cleaned out the TB, replaced the intake gasket, replaced the TPS, and replaced the MAP sensor. I left the battery disconnected to see if it would reset the computer. Well, I drove it to work this morning and it was still idling high, but this afternoon on my way to meet my wife for lunch, it started idling normally again.

So I'm happy for now....but now it's on to my TJ.... and that's another story.....lol

Thanks again for the help!

Marty