idle problems with 1997 Cherokee

[stcif]

I have a 1997 Cherokee SE, 6 cyl. with 82,000 miles. For about the past six months it has been developing a rough idle when the engine starts to warm up and gets quite rough when fully warmed up. I replaced the plugs, wires, cap and rotor and it hasn't gotten any better. I had the catalytic converter tested and that checked fine. I noticed there are three sensors around the throttle body. I believe two are the MAP,and throttle position sensors and I was told the other was what replaced the older EGR valve. I cleaned the one sensor which consisted of a metal probe like object which was all carboned up. The idle is still rough. When it starts to idle rough the engine kind of "catches" itself and then revs up a little and the idle smooths out for a little while. I am wondering if the fuel pump needs replacing. I researched the pump and found the filter and fuel pump pressure regulator is part of this pump assembly. Can anyone give me some advice as to what they think may be causing this rough idle. Air filter is new and I change the engine oil myself about every 2000 miles. Thanks.

[Dale Aeppli]

Originally Posted by stcif

I have a 1997 Cherokee SE, 6 cyl. with 82,000 miles. For about the past six months it has been developing a rough idle when the engine starts to warm up and gets quite rough when fully warmed up. I replaced the plugs, wires, cap and rotor and it hasn't gotten any better. I had the catalytic converter tested and that checked fine. I noticed there are three sensors around the throttle body. I believe two are the MAP,and throttle position sensors and I was told the other was what replaced the older EGR valve. I cleaned the one sensor which consisted of a metal probe like object which was all carboned up. The idle is still rough. When it starts to idle rough the engine kind of "catches" itself and then revs up a little and the idle smooths out for a little while. I am wondering if the fuel pump needs replacing. I researched the pump and found the filter and fuel pump pressure regulator is part of this pump assembly. Can anyone give me some advice as to what they think may be causing this rough idle. Air filter is new and I change the engine oil myself about every 2000 miles. Thanks.

HI, IT SOUNDS LIKE THE AIR CONTROL VALVE ON THROTTLE BODY NEEDS CLEANING. REMOVE AIR FILTER HOSE FROM THROTTLEBODY LOOKING INTO THROTTLE BODY BORE ,YOU WILL SEE A SLOT IN THE BORE THIS IS THE AIR CONTROL VALVE , ( CONTROLS IDLE) . GET A SPRAYCAN OF THROTTLEBODY CLEANER, USING SMALL STRAW ON SPRAYCAN, START JEEP HOLD ON HIGH IDLE SPRAY INTO SLOT TO CLEAN VALVE AND PASSAGEWAY CLEAN GOOD ALONG WITH WALLS OF THROTTLEBODY SHAFT AND BUTTERFLY CLEAN IT GOOD. DON'T SPRAY SENSORS OR THEIR PLASTIC HOUSINGS. HOPE THIS HELPS DALE [email protected]

[skyler4321]

Hi
I have 2000 jeep is doing that exact same rough idle behavior that is described above.
I have no clue what is causing it.
Thanks
Skyler

[fredjacksonsan]

Hi Skyler, and Welcome to AF.

Please check the date prior to posting; if the thread has been idle for more than 30 days, start another.

That said, it could be the sensor Dale mentioned, or it could be the Crankshaft Position Sensor. Do a search for the CPS and you'll turn up a wealth of information.

If those don't solve your problem, start a new thread with lots of detail.