AzItaliaSS

1999 XJ sport.

Got in XJ to drive to work, noticed coming off freeway by sound and feel, RPM's not coming down as fast as normal. When stopped XJ has decided to idle at 11-1200 today instead of usual 650. Obviously needed little more pressure on the brake as it wants to go. Pulling into work parking lot while gate opens, I release brake as a test to see what it does, no gas foot, XJ obviously starts moving as its idling at 1100 and slowly climbs to near 1900-2000 and shifts to second. I then brake and pull into a parking spot. Idle slowly goes back towards 1300-1200 range and I shut it down.

Two years ago multiple sensors were replaced to include tps, less then a year ago it had full tuneup(wires,plugs,etc.) two months ago it had full coolant flush, hose change, thermo change and radiator.

Any help would be appreciated.. possible sensor again? maybe filter is now too dirty?

Thanks guys

Kalali

I would start by checking under the hood to see If any of the vacuum lines have come off. Then move on to cleaning the idle air control valve.

AzItaliaSS

Yeah ill have to check that, I replaced it about 3 years ago along with sensor, but after watching a yout tube video, I see how it could get carboned up in there.

md21722

Vacuum leak, idle air controller, or throttle position sensor.

When my TPS started failing, I was driving on the highway and took my foot off the gas coast off an exit lane. The engine revved up as if it was down shifting. Then another day I started the jeep and it started normally but soon was "idling" as 2000 rpm. Then it slowed down in increments. On the way home from work that day it was cutting out a bit. I stopped at the dealer for a new TPS.

Problem solved.

These sensors can be tested, but the shortcoming of the tests is that we usually perform the tests with a cool engine, but the sensor may work fine cool and fail when hot.

Roler

I'd check and clean IAC and clean throttle body, especially around the valve, test TPS 'sweep' with analogue meter and check vac lines and vac leak. Let us know how this goes .