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2300 rpm at idle WOW!

K

ken johnson

NAXJA Forum User
Location
Kentucky
My 89 xj started up this morning as usual except the idle went to 2300 rpm. I had to go to work so I took off. I drove 35 miles with 6 traffic stops along the way. No change! I turned it off and went in to work. What should I do this afternoon? I'm concerned it will blow up. NEED HELP TO GET HOME. IT'S FINALLY FRIDAY! Thanks
 
sounds like a sticky IAC, I'm sure someone will chime in .
 
Yup, IAC. Take it off, clean it with TB cleaner. If you want on the way home stop at a parts store and spray some into the passages on the TB, might free it up for the ride home.
 
I'd check vac leak first. Too many hard lines that can crack.

Make sure the TB to MAP line is on properly. Check all the lines around the airbox, including that whacky junction block by the PS pump. If you find any cracked, some elec tape can patch it or use short pieces of vac line to repair.

IAC likes others say is another suspect but you'll need some tools too to remove it.
 
If this is the first time you have had the high idle it is likely the IAC. Try removing and cleaning but it is likely to need replacing. Also check and make sure your throttle body plate is closing completely. That is a problem on older XJ's. The TB wears over time. A quick way to check if the IAC is stuck open is to cover the TB opening while the engine is running. If the engine does not immediately stall your IAC is stuck open or you have a major intake manifold leak. If it dies right away, check your throttle plate. While you are cleaning the IAC it would not hurt to adjust the throttle position sensor (TPS). There are online references to show you how.:idea:
 
One thing not mentioned is the EGR. A sticky EGR can net you quite a high idle.
 
HELP! Runaway Idle HELP!

89 xj. 4.0. Idle at 2400 rpm. Cleaned air module. It was very dirty. Still have high idle, higher than before cleaning. I've unpluged IAC and it made no difference in rpm. How do I determine it needs replaced? What is my next step? Please help!
 
Re: HELP! Runaway Idle HELP!

Check your EGR.
 
A stuck open EGR would cause a low or stumbling idle due to passing exhaust gases into the intake.
 
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