i would chang the coil pack first just to see if it would cure the problem it is cheaper than a cat but it would nock the what if senereo down dont mind my spelling allways been a bad speller. on the first not do the coil pack then if it did the same with the missfire there some detonation some where inside the cylender do a fuel clean in it use sea foam when running the car it will clear up some of the funk

 

I have replaced the coil pack and I have ran sea foam.

Thanks

 

Thanks guys, I will try your suggestions next week!


no it isn't a dumb idea, i actually bought a gtp s/c (for $100) and was planning to put it on my lumina until my friend accidently sold it at an auction at his house lol. I'd imagine u would need a ECU out of a GTP, but I don't know how the GM ECUs work..(I am used to Honda/Acura ECUs).

 

the engine runs great now, just misfires, lol. i dont want to drive it too much if its backfiring into the intake manifold, due to the cat being red hot might have messed upi either a. the cat tself, or b. the o2 sensor. which one is more probable?

 

Causes Of Converter Failures
Fouling, clogging, melt-down and breakage of the ceramic substrate inside a converter are common conditions that can cause problems. Plugging is usually the end result of a melt-down, which occurs because the converter gets too hot. This happens because the engine is dumping unburned fuel into the exhaust. The excess fuel lights off inside the converter and sends temperatures soaring. If it gets hot enough, the ceramic substrate that carries the catalyst melts.

 

ok as of today i had my car plugged into a scanner, i got:

P0300 - Random/Multiple Cylinder Misfire Detected

p0420 - Catalyst System Efficiency Below Threshold (Bank 1)

I am replacing my cat asap. that has to be it..everything else has been addressed!

 

ha ha, i just got the same codes today, bank one sensor is your 02 , pre cat....... let me know what you figure out asap, im thinkin im going to have to replace cat and 02 sensor,

 

wow, after reading this post i think i have a great ground for starting to figure out my solution. at cold start up, i have horrible misfires after about 30 seconds of starting the car. typically lasts for about a minute then the car idles fine. doesnt throw any codes. it started doing this after i did the SS m90 kit install. runs 33# injectors, had it fully tuned and couldnt find anything that would cause this. car does idle slightly rough, not horrible though, and does spit a little gas out of the exhaust. changed the wires, coil packs, spark plugs but never had my ignition control module tested. the cat is a hi flow cat, and i have a ceramic coated ported exhuast manifold and crosspipe. im gonna check to see if my cat gets red after i drive it for a while. anyone tell me more about the ignition control module and how to change it/locate it in engine bay.....sorry dont know much about the ignition. this is for a sixth gen

 

damn good luck with that man..it is probably a lot harder to track down a car with all kinds of aftermarket parts. anyway, my car does the same thing sometimes and I am almost positive it is my cat.

 

right, but that only means the cat is making it through wrong codes correct? my o2 sensor is fairly newer than the exhaust system, and GAH!

maybe i'll take a damn multimeter to the o2s before i replace the cat lol. does anyone know what resistance should be running in both o2 sensors?

thanks