I wasn't contesting the fact that it would misfire. Only that it won't always set a misfire DTC.

 

Ok, a little more progress was made. The EGR valve was put back on and the engine definately has plenty of spark to ignite the fuel. However, gas was found in the crankcase, so apparently the engine is getting too much gas and flooding. By having the power cut to the fuel pump, the extra gas in the lines allowed it to run for about 10 seconds. We think it may be the injector or regulator.

 

Replaced the injector/regulator, all six poppet nozzles, and the gasket. Going to change the deluted oil tomorrow and see if it runs.

 

I made a lot of progress on the Blazer. After replacing the injector yesterday, I changed the oil today and tried to start it but it just cranked and cranked. I took the #1 spark plug out to check for spark and when I cranked the engine it fired right up and ran... although really rough... It didn't run with the plug in, so thinking it could be a valve problem, I ran a compression check and got a reading of about 130 psi. I took the #2 plug out and it ran just the same as it did without the #1 plug, but still wouldn't run with all the plugs in.

I looked at the catalytic converter and there was a thick black substance coming from the exhaust leaks I found a while ago. I banged on it a bunch with a hammer and apparently knocked off the little cap that is on the side of it, because when I went to try and start it again, it started but poured almost black smoke out of that hole.

 

Sounds like your catalytic converter is shot.

 

Took the catalytic converter off today and emptied all the guts out into a bucket. It was broken into small pieces and packed full of carbon. Once it was back on, the truck ran fine except for the fact that the cap is still missing on the side of the converter so there is a big exhaust leak.

 

Still not sure why it would start on 5 cylinders but not on 6. would the 6th plug firing cause enough additional back pressure to keep the car from starting? I don't think so.

 

I can believe it because w/o the plug, when the exhaust valve opens, then all of the exhaust in the manifold can exhaust out the plug hole. So, have you tried to fire her up without the cat to get proof positive?

Regards,

Thomas

 

I took all the broken guts out so there is nothing in the cat that can get clogged. It's basically just a pipe now. When I started it up, it ran fine and idled fine but the little cap on the side of the cat is missing so there is a pretty big exhaust leak.

It is weird that it ran on 5 cylinders and not on 6. But, what you said does make some sense, because I was wondering where the exhaust from the other cylinders was going while it was running.

 

Do you have a welder? If it's not too big of a hole you can just fill it, or get a little piece of steel to put over it and weld in place. Then you're done until it's emissions time.

Regards,

Thomas