90 Cherokee High Idle Speed

[$Kent$]

1040302

I have a 1990 Jeep Cherokee with a 4.0l I6. I just picked this beauty up for real cheap and I'm loving it. Anywho, the engine seems to work fine, cranks about 5 or 6 times before it starts but always starts, but when I use it, especially offroad, the idle speed increases.

If I use it for about a half hour offroad in 4wd, I eventually don't need to use the gas pedal, I'm fighting the engine with the brakes...not my cup of tea.

After about a half hour, when I put it in park or neutral it idles up to anywhere between 2500 and 3500 rpm.

The initial idle speed at cold start is about 1200 rpm.

I would really like any ideas at all.
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[TerryMason]

1040321

Could your throttle linkage be sticky? I'd work it with your hand, and see if it travels freely, if not, spray it with some WD40
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[greep]

1040347

i've been battling a pain in the butt xj for 2 weeks and finally got it fixed!
i would say, take a look at your egr valve. pull it off and clean it with carb cleaner. they get hung up after a while and act like a vacuum leak. a vaccum leak on a fuel injected engine will raise the rpm. the computer thinks its you getting into the accelerator and compensates by putting in more fuel, thus high rpm. also do the same with the idle air control motor. these can get stuck from carbon as well. do not unplug the idle air control solenoid with the engine running or the key in the run position. it will spike the computer.

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[$Kent$]

1040360

What exactly is the proper way to clean the egr valve? can I spray the carb cleaner directly into the valve or just on the external parts?

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[greep]

1040383

best way to clean it is take it off. you may or may not break the gasket. the gasket should be available at the local auto parts place. on the I-6, the valve is located just under the throttle body and is bolted on the side of the intake. you remove it and clean up the passages as best you can with a brass wire brush and carb cleaner. i would also clean the idle air control motor passages while your at it.


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[az427cobra]

1040384

try cleaning your throttle body, use some carb cleaner inside of it. Good luck!
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