Firstly, I've ran through all the threads on this issue and none of the fixes have worked so I started a new thread...I've checked the fuel pressure (47.5 psi), replaced the tps, aic, and cleaned the throttle body. There's no vacuum leaks that I can detect and the engine is not misfiring it just won't idle without surging. I've also looked down by the exhaust manifold by the O2 sensors for cracks and have none. It idles o.k. when cold but when it gets warm it gets to the point that it won't even keep running. Ideas? This is driving me crazy not driving my Jeep...

 

Also, I hooked up an obd and there are no codes. It did throw a po442 and po455 but those are evap codes and shouldn't have anything to do with driveability.

 

Have you tested any of the components or just been swapping parts, any cel or stored codes? You said it's a 2001, how many miles, owners? How about the rest of the vehicle is it in excellent condition or a beater? Have you checked compression or done a leakdown test?

 

no leakdown tests, second owner, 112,00 miles, it's in vg condition. i've had it for two years and other than the evap codes, no issues. The engine itself is running fine, just this surging that almost seems like a vacuum issue. I haven't done an ohm test on the components but did swap out the aic, and tps to no avail.

 

I haven't checked the voltage at the map sensor. Maybe this might cause this issue...

 

What is the vacuum @ idle? Do you have a scanner that can read live data?

 

No way to check vacuum @ idle. My buddy's running a map sensor check tomorrow. Other than the big three vac lines hood topside what else could be causing this. I'm not thinking the egr or the pcv would cause this. Even the dc techs I've talked with are stumped as I've exhausted every avenue they're used to taking. Could a plugged cat do this? Man, I just don't know. Ill see about vac at idle tomorrow if no one posts any other avenues of solving one of the great jeep mysteries.

 

Solved, bad MAP sensor.