Hey my mustang munchin' brothers, gotta problem I hope you can help with. Recently pulled and polished my runners and plenum on my Paxton equipped 5.7 tpi. Also installed new valve covers. After reassembly, car fired up fine, but after a couple minutes starts to idle rough and gets progressively worse to where i have to shut her off. Also getting a little smoke off one side of the runners/plenum which might be left over polish burning off, don't know. It's not tripping any codes either. I tried the brake fluid test around all the runner/plenum contact surfaces with no result. I used new gaskets all around. Could it be the cold start injector hanging open? when it starts idling rough it spits a ton of unburned fuel out of the pipes. Is there any other possibility than a vaccum leak. Your ideas are greatly appreciated!

 

Check your 02 sensor... it could be that when you go into a closed loop, the O2 is all facked up and could maybe be crappin up your idle... What kinda gas you putting in? Maybe Knock sensor is feeling a little detination and is pulling out timming.. In a SC'ed car, That would be my first guess.. but it was my 2nd... oh well.. Sounds like a nice car. Good luck
Alex

 

Replaced the 02 sensor, no change. However I noticed this symptom; I had drained the coolant and was replacing it when I fired the car back up. I didn't have enough coolant back in yet and the coolant temp rose alot faster than normal. The idle went bad quicker and worse than before. I'm beginning to think this problem is coolant temp related. Also, does the same thing with the cts disconnected. Any help would be appreciated!!

 

Swap out the CTS, check out your timing, and make sure you didnt forget anything

 

How hot did it get???

 

I didn't let her get too hot before i shut her off, 200 maybe. Will try replacing cts next and check timing. Thanks