ive been having a cylinder 7 misfire for a few months now. its been driving me crazy. i replaced the cap, rotor, wires, plugs, ignition coil but havnt had an improvement. heres the symptoms. i have no power. takes me about 20 seconds or so to get up to 60 when it used to take me under 8 easy. between 1400 and 1700 rpms and then again at 2000 to 2300 it bucks wildly, shutters like a sob and so on. when im under acceleration the cel blinks which means random cylinder misfire? i just cut the cat off. haha.. take that california emissions. its obviously bad. theres a hole the size of a golf ball through the honeycomb center of the cat. there are also chunks of stuff rattling around inside. so what could be causing my misfire? yall have any ideas? and sry for the long post, but theres a lot to tell.

 

since you've basically done a tune up and... have taken care of the cat, I would read up on the cracked heads.

 

I have gone thru this problem many times at the shop, and a tune up didn't fix the misfire. Replacing the cylinder heads did fix the problem. If you are 80k, its time.

 

do a compression test before you do anything rash.

 

dhvaughan, I thought a leakdown test was better for testing for cracks along with leaky valves. i know a compression test is less involved but wouldn't the leakdown test provide a better diagnosis?

 

I agree! But then again it wouldn't hurt to do a compression test. Out of curiosity have you checked your fuel injectors. Maybe its not spraying correctly or maybe not at all. Too much air? My TB was cracked and it had a real hard time taking off cause it was getting to much air.

 

im gonna do a compression test in the next few days. how would i go about doing a leakdown test? i pulled the injectors and cleaned em bout 3 months ago, but i might pull em again and see whats up.

 

The bad plenum is what is probably causing the misfire, and the reason the cat went bad to begin with. The o2 sensor will also be in question.

 

zman17 has a good point because you probably blew it out when you had the supercharger on there

and like i posted on your other thread
man sorry your having bad luck with the truck,, its sucks, hope it get better for you

 

swap fuel injectors. Could have a bad one. Also check the wiring to the injector