High idle on startup

[RaiderXJ]

When started, my idle soars to about 2500rpm's. It sometimes will stay at 2500 for a second then slowly start to come down to normal (600-700) Here's what I've done so far:
-removed and cleaned the Tb, removed stepper motor to clean.
-adjusted TPS
-checked for vacuum leaks, couldn't find any obvious ones.
Any other ideas?

TIA
RaiderXJ

 

[PaulJ]

On my '87, it seems like the C101 connector contributes to this. It's a bear to clean the old grease out of it. You might try disconnecting and reconnecting it. It's the big connector on the firewall, just above the brake booster

 

[CheapXJ]

I've found that if it sticks at 2500 rpm, I just disconnect the IAC and reconnect it... then it works fine for a couple days.

I'm guessing that the IAC is messed up?

 

[Greg Smith]

Ditto on the c101 connector comment. Also when the idle spikes at startup and stays to long then usually you tps or its connectors are going bad per my dealer tech and per my own experience. A new tps fixed my problem. Greg

 

[sidriptide]

i had the same problem on my '87 last week after i "gunked" the engine.. ididnt replace the TPS yet but i will.... when it was over-revving i took a small flat blade screwdriver and bumped the arm on the TPS a few times and it came down..... after it dried it was fine. i had an '89 XJ that the TPS went bad from getting wet and it messed up my trany shift points.

 

[88 Jeeper]

hey sidriptide..

what all did having a wet TPS do exactly besides the shift points? i think i have that same issue except i have high idle (an extra 400rpm or so) and the shifting is slightly off and seems tps related. idle motor is new and vac lines are good..

any info appreciated!

 

[sidriptide]

to 88 jeeper....
this time all it did was make the engine scream and p@#$ me off.... started and stopped the engine a few times and got the idle down each time.... by the time i drove home i guess it was dried out enough that it isnt doing it now... its not a daily driver , thank god.. it didnt affect my shifting this time, but a few years ago i had an 89 that i "gunked" and within a day i guess the trans shift points were all messed up... regardless of throttle position it would bang thru the gears and hit o/d at like 35 mph... took me a while to figure that one out... but it never went away even after it dried out.. but the idle never went up on that truck... the TPS has its fingers in quite a few systems apparently and each is affected differently.... hope you figure it out soon..