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94 XJ fast idle like 2000 rpm

B

blacklab

NAXJA Forum User
Location
Canada
I'm about ready to go back to being a Ford man. I bought a 94 XJ in August. It ran great no issues. about a month ago it wouldn't start without giving it throttle.
I cleaned the throttle body, and the idle air control motor. I seemed fine for awhile, then the idle Rpm kept increasing as it warmed up, it now gets up to 2000 rpm at idle.
I've gone through all vacuum hoses, checked the manifold bolts.
I replaced the TPS, but am not sure it is the right one, I got it from a friend that had a bunch of parts from a dealership.
Do I keep throwing parts and money at this thing or what? There are no junk yards handy so I'd be buying new parts to test.
 
No you test the vehicle you have. Test for vacuum leaks by spraying a fuel source at gasket edges, hoses etc. If RPM rises due to the increased fuel source you have a vacuum leak. If you have access to a multimeter you can check for output out of the TPS. One lead backprobes TPS and the other on a good ground. Output at closed throttle should be about .5 Volts and WOT should be about 4.5 volts. You cleaned the IAC but how new is it?
 
I don't own a multimeter (yet).
What is driving me nuts, is that it starts fine, runs great, and at times idles at 750 rpm.
I've repaired vacuum leaks, in fact I can't believe it ran with the number of bad hoses it had.
Is there a way to test the IAC?
Could the temp sensors have anything to do with this?
The other thing is if I let it run at 2000 rpm idle it will eventually come down to 750 or if it cools right down it idles fine.
 
Temp sensors could yes for one reason. The first sensor your computer looks at to set starting fuel trims is the ECT sensor. If it is biased low, meaning it reads a colder temp than actual then it will add more fuel at start up.
 
Well I replaced the IAC this morning, so far so good.
I think I getting this Jeep thing figured out, just keep changing parts till it runsright.
 
joejeep92 said:
It doesn't take a lot of equipment to diagnose correctly.
Click to expand...

And the money saved by buying a diagnostic tool will more than likely be made back the first time you don't just "throw parts at it"

One of my friends almost dropped $250 on a mass air flow sensor for his audi when all it took was some poking around to find a loose ground.
 
there are coupons for free multi-meters from harbor freight in just about ever JP and fourwheeler magazine I own...no need to buy anything, they really mean free. just pick one up, and learn how to use it and save yourself a ton of money down the line...it's a jeep, you're going to be working on it, probably more than you're expecting...gallon jugs of gojo are a must....a jeep is worth every busted knuckle.

also: home depot has them for around $10, if a harbor freight is too far to justify fuel cost.
 
I was worried about being bored when I retired, so I bought a Jeep.
Sure solved that problem!
Would a multi meter tell me my IAC was only working part time.
 
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