View Full Version : 89 XJ 4.0, idles at an amazing 1,800RPM !

11-28-2007, 11:53 PM
As the title states, my lil XJ has started to idle at about 1,800RPM :eek: ....silly I know, any ideas as I'm new to this engine ! I took it wheelin this past sunday, rocked it a lot and managed to unsettle some vacuum lines but have reatached the ones I could find to make it driveable again but that idle is a stumping point, HELP !

11-29-2007, 10:08 AM
early xj's are know for throttle position sensor problems causing a high idle. carefull though they need to be adjusted properly when installed.

12-02-2007, 09:30 PM
Welp, my scaner reports the TPS is functioning properly, 0 to 100 when the pedal is mashed in a smooth motion, checked each and every vacuum line on the rig, everything is connected to where it's supposed to go.....I cleaned the IAC, throttly body n intake all nice, stumped as I might be I"ll figure the fucker out and get it back on the trails. Oh anyone know of a place to get front sway bar disconnects for a stock height XJ ? I'm planning on simply removing the back one completely......don't need the thing.

12-02-2007, 11:40 PM
high idle can also be caused by an intake leak. Mine did the same thing check it by spraying carb cleaner or similiar along the intake manifold if the idle drops that is where the leak is

12-04-2007, 06:19 PM
Same thing was happening to me when I first got my XJ. Drove me nuts! What I discovered is that sometimes I would put my foot into it a bit when starting the beast. The idle would be all over the map until I shut it off for 10 minutes or so. It seemed like the idle would stay at whatever RPM I was at when I depressed the clutch pedal. Once I realized what I was doing and stopped doing it, the problem only occurs once in a blue moon now. I think "assisting" it to start messes up the idle sensor somehow.

I dunno, might be worth a shot.

12-13-2007, 06:25 PM
eh I've just about thrown in the towel here with my XJ, can't seen to figure this out.....high idle, extremely lousy fuel economy, like 200K to a tank if I"m lucky,I"ve checked everything and things sem to be working correctly.....I"m at a loss....mebbe it's time to consider an engine swap.....ugh

Growly Gorilla
12-13-2007, 11:35 PM
If you have a scanner what's your iac counts? And what are your O2 sensors doing? long term fuel trim? Is it a MAP or MAF system?And check your ECT(engine coolant temp.sender) May not be working and staying in open loop.

01-04-2008, 09:17 PM
Welp, there might be an '89 XJ posted for sale for parts soon.....she's not co-operating, got the idle down but she drinks $70 in gas in less than 200K......really really burning my rear.....

01-16-2008, 11:06 PM
Ok.....got the idle down.....by pinching off a hose that goes from the intake manifold to the valve cover.....noticed that the hose is screwed....nothing a new hose will replace but the round thing that goes into the valve cover is loose....anyone know where to get a new rubber grommet for it ? oh and to agree with lornix, 89 XJ - A complicated system of ropes and ponies and hoses....