I have a 2001 Chevy 2500 ECSB that has a bad miss. Hooked it up to the computer and it says misfire on number 5 cylinder.

So this is what I've done so far:

Installed new spark plug and spark plug wire
Switched coil pack with number 4 cylinder (good spark also)
Switched fuel injector with number 2 cylinder
Compression check - 150 psi all cylinders
Noid light - flashes

Any guesses on what's going on or what to do next?

 

you got a broken valve spring?

 

Did you see if the coil was firing for sure? I have seen broken wires at the coil.

Dustin

 

Yeah the coil is firing good. I had switched it with the number 4 cylinder to no avail.

 

How many miles are on this engine? 150 psi sounds low.

I had a P0303 on my truck that was being caused by a clogged cat. It just decided to "pick on" #3, when everything else was okay. You might check your backpressures next.

 

I also had misfire codes due to bad cat. sometimes random and sometimes cylinder specific.I would not get codes until I got on it and took it up into higher rpm's.

 

It doesn't have a broken valve spring.

The truck has 140,000 on the engine.

The cat is interesting. Relatively new exhaust and headers (2 months) on the truck. Kept factory cats.


How do I check backpressure?

 

Yessir, clogged cats will give you a misfire, among other things. You may find that the engine will not want to rev up past 4k if the cats are clogged.

 

run that joker with open headers and see if it fixes it (only long tubes.. dont do this if you have shortys) but if you have shortys.. there pointless...

O2 sensor could be jacked up but usually it will throw a o2 sensor code... i would take the cats out and see if that works...

what about a leaking intake gasket?? could be getting air from there instead of threw the intake....

 

does it do it in park???? idle?? or only under load????