2000 Expy, AWD 5.4 with 51,000 on the clock, was running great after installing new fuel pump and cleaning the injectors. Installed new Flowmaster cat-back exhaust system, drive it around and running great. Started it up this morning and it was missing and barely running. Opened the hood to check it out and noticed that the right cat was glowing ORANGE hot!

Checking it out and pulled codes after running it for 15 minuets. I have miss fire detected on 1,5,3,4. What would cause this sudden poor running? BTW, the cat isn't glowing now, just running really bad. When I try to rev it up, it sounds like an exhaust leak at the right doughnut gasket???

All thoughts welcomed.

 

Looks like you have a major exhaust leak on the pass. side. An exhaust leak will cause engine to run lean. Are the misfire codes the only codes?

 

Yeah, cleared them and ran it for another 20 min. This time 1,4,3,8 miss fire.

When it first happened, it only ran for about 2 min. before the CAT started glowing. Not just CAT hot, melted the undercoating on the frame next to the front CAT hot like I held a rosebud on it for 5 minutes.

Colapsed CAT???

 

By no means am I an expert, just a question to ponder...

Could it be a stuck open fuel injector, or other injector problem?

 

Jesus man you've not had good luck at all with that thing.

 

HAHA, Man you got that right. Guess that's what happens when you let em sit for 8 years.

 

Clogged cat...

 

What I'm thinking too. Gotta get some OX for my tanks before I can get the exhaust off.

 

It's glowing red for a reason... it's clogged which will cause multi mis-fires... now need to find out what caused it to become clogged in the first place...leaky injector...bad plugs that were mis-firing...

 

Vehicle has been in storage for 8 years. I just replaced the fuel pump, fuel tank pressure sensor and cleaned the injectors. All of this last week. Installed a new cat back exhaust system on Saturday. How can I check for leaking injectors?