Ok, ever since I plugged in the plug on the CTS (coolant temp sensor) that was broken off, the car runs like total ***. No CEL anymore, tranny shifts great. It does NOT stutter/bog when taking off normally, but when attempting to WOT, or passing/ going over 2500-3000 rpm 3/4 throttle, it will bog and stutter, no backfiring, no flashing CEL. I just did a tune up on it today, but it did it before the tune up, after I plugged the CTS in. Unplugged it runs great but the CEL is on. So plugs, wires, cap, rotor, air filter are all ruled out. Anyone have a clue what it could be? I got good oil pressure, good battery voltage, idles perfect, etc.

plugged a plug? :?

did you put a new sensor in? maybe im just not understand the problem

No I didn't put a new sensor in. I found the sensor unplugged, thats why the CEL was on, so I fixed the broken plug and pulled the battery cable, put the cable back on, started it up, and the CEL was gone, but now it runs like crap.

Also forgot to mention that it does have a new $400 ACDelco FP. There is a fuel leak, but I don't think enough to make it run crappy? it just seeps out of the line.

Might be enough of a pressure drop to hurt it.


What'* pressure at?

I didn't check it yet, but its not a bad idea to do so. I did hear that the CSFI system is extremely picky about its fuel pressure.

That really does sound like a fuel pressure issue, especially since you say it only happens at high rpms/WOT situations.

I agree, plus data is knowledge.

Check fuel pressure
Look for any vacuum leaks
A higher rpm clog like sound. Cat maybe? consider unscrewing the front O2 and starting it.. that should remove enough backpressure for a good test.

Was the fuel filter replaced during your tune up?

It was replaced in Dec. Truck has a new tank, pump and sending unit.