My jeeps idle surrges and also idles very low when cold (200rpm) and then high after its warmed up (1200rpm). The jeep had fuel system problems when i got it so the tank, fuel pump,fuel filter, fuel pressure regulator and injectors have been replaced. I have done everything that is normally recommended, I have done a plugs, wires, cap, rotor, cleaned electrical connectors, refreshed grounds, clean iac, checked and adjusted two tps, and cleaned the throttle body. The jeep drives fine and runs much better than it did before but the problem is still there.
Im not sure what to check next,thanks in advanced for the help.

 

I forgot to add that the jeep has 164K and I think that it may have a leak in the exhaust manifold gasket but Im not sure if that would cause the idle problem.

 

Problem solved, I did some trouble shooting and found that if ran better with the O2 sensor unpluged so i replaced it and it runs great now.

 

Note from DJ
Thanks for posting the solution

 

Absolutely X2, DJ. Pretty sure anytime idle is fluctuating with a Renix, (87-90), the O2 sensor has likely crapped out.

Mine was 15-20 something secs, with a stone dead O2 sensor.

 

Note to from DJ for DFlintstone
Have a look at this Link
TITANIA 0XYGEN SENSORS Techtips
Tomco Techtips from 1994
http://www.tomco-inc.com/Tech_Tips/ttt20.pdf
Information from Page Two; Bottom of Right hand Colum
Diagnosing these sensors:
When diagnosing these sensors, first check the heater. With the sensor disconnected, use an ohmmeter to measure across the two terminals for the heater. It should be somewhere between 7-10 OHMS on most sensors. Look for the appropriate resistance values in the service manual.

Since the Titania sensor doesn’t produce a voltage, we can’t bench test it to see a voltage change. But, we can hook up an ohmmeter to the signal wire and ground and read the change in the resistance of the Titania as we heat the tip.

Of course these sensors can always be checked in the vehicle by using a DVOM hooked to the signal wire that goes to the computer. The voltage should shift between 0 and 1 volts, or 0 to 5 volts, depending on your application.

 

While you're in this mode, go to www.cruiser54.com and do Tips 1 through 5.

 

Some more on 02's here. Note EcoMikes link up top in this thread.

https://www.cherokeeforum.com/f2/ren...ce-rms-133153/

 

I know I posted that my problem was solved but it was not, after a few days the problem was still there just not as bad. I changed the intake/exhaust manifold gasket and im glad I did most of the bolts where loose and one was missing. Its been a few weeks and its running great.