rpm tacking up

When I first crank my jeep sometimes it will tack up to 2000 rpms and stay there for about 45 seconds. Why is this?

iac needs to be cleaned or tps is bad or out of adjustment, depending on what year you have.

or a vacuum leak

Its an 88 strait 6. what is the iac and the tps. Where are they located?

kbradner said:

Its an 88 strait 6. what is the iac and the tps. Where are they located?

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They are both on the front side of the throttle body.

Search the oem forum for threads on "Idle Air Controller" and "Throttle Position Sensor". Lots of pictures, and how too's already posted here.

Also, search and read about "High Idle" problems and "high idle ground" problems for a no cost, fix that is frequently the problem too!

The three letter accronym search terms (like IAC, TPS) do not work here at , but they do work if you search Google for say "IAC ", so I am told, also IAC* seems to work in the search engine here.

adding to what ecomike suggested, the 1988 4.0l fuel injecton straight six is controlled by what is called the RENIX(renault and bendix) fuel management system. typically, the 87-90 xj's will be refered to as the renix 4.0

with renix system, there are no codes to read(unless you have an expensive hard to find scanner) when diagnosing a problem with the sensors. that being said, to test the TPS you will need a voltage meter and a testing procedure from the factory service manual. you may be able to find the testing procedure somewhere on this site.

the iac is on the front left side of the throttle body and can be removed and cleaned with throttle body or carb cleaner, while your at it, the throat of the throttle body should also be cleaned.

the tps is on the front right side of the throttle body. do not clean the tps with any type of cleaner. the tps needs to be tested following the fsm procedure.

also try this page

http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm