88' renix rpm revs?

Hi i am trying to figure out y my xj is reving up to like 3-4k. I know it will happen when i am driving and i start to slow down for a turn or something and the rpm's jump just a little bit when it down shifts, after that when i park it the rpm's jump up to like 2k and do not drop until i shut it off, then when i start it back up sometimes it jumps up to 3-4k and wont go down until i shut it of and start it several times. I took it to a shop and the guy there really could not figure it out and tried to charge me $688 to change out the IAC motor and he said the intake manifold had a leak in the seal. Well could any of these cause this problem or should i be looking else where? Thanx for any input jimmy

If you do have a leak yes it will.

ok so i replaced the iac motor, so next would be fix the leak and go from there?
Is that pretty easy to do?

This is actually very common on renix era XJ's.

http://www.naxja.org/forum/showthread.php?t=905849&highlight=renx+files
Read this thread (I know it's long) there is some very good info in there and there is a good chance that you can get it resolved.

Did the $688 include some lube and the mechanic whispering sweet things into your ear? The IAC takes about 5 minutes to change and costs like $30. Even if that included resealing the intake, your getting robbed.

There are 4 things that I would suggest to fix your problem:
1. Clean the throttle body and IAC passage
2. Make sure the Intake is sealed up
3. Make sure your grounds are clean and solid, particularly the ones that are attached to the dipstick tube retaining bolt
4. Make sure your TPS is adjusted properly. This link will help you with that. http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

Good luck

Yea no he was not nice it was more like prison than romance...Hahahaha. But yea thanx for the help im gona try and tackle it this weekend. Seems like there is alot of info on idle problems on these renix's.

I can usually unplug my TPS and the idle drops to normal, reconnect till next time.

Harlee&Tahoe said:

I can usually unplug my TPS and the idle drops to normal, reconnect till next time.

Click to expand...

Damn thing is hard to drive with the TPS unplugged but you must have a solition. Please share!!!

only time my 89 reved/idled to 3k rpm was because of the tps getting wet or out of adjustment. a vacuum leak, intake leak, or bad iac wont take it to 3k rpms.

sometimes unplugging, clean and lube the connection, and reconecting will solve the problem if the harness got wet.

90Blue_XJ said:

Damn thing is hard to drive with the TPS unplugged but you must have a solition. Please share!!!

Click to expand...

Harlee&Tahoe said:

reconnect till next time.

Click to expand...

Check adjustment and voltages in. Mine drives alright w\out TPS slight hesitation, feels like fuel trim is by O2.
What about checking grounds. Might as well check all including "RENIX Killer"
TPS is grounded to ECU