1990 Jeep rough idle
 

I have a problem 1990 jeep cherokee 4.0. Rough idle after it warms up. The O2 sensor performs normally until it is closed loop for about five minutes. It then locks on 4.98 volts, the short term fuel trim eases its way up to the max of 255(lean) and the long term fuel trim locks at 95, and drops to open loop. I have replaced the O2 sensor(after market), fuel pressure regulator, map sensor, EGR valve, temp sensor, idle air control motor. The customer has replaced the computer with one from Autozone.

Any help would be much appreciated.

Thanks.

Jack

it's a heep; what do you expect? BTW this is MercedesShop.....