Need a little help. I have a 2002 F150 4x4 V8 4.6L. It has been running a little rough as of late and I have gotten codes that say it is running lean on the right bank and a misfire code as well on 1 and 2. I have replaced both coil packs and both O2 sensors on that side. Also have just replaced all 8 fuel injectors and it has a new ECM. The truck is still running a little rough so that got me to thinking I might have a bad cat on that side. I let the truck run for about 15 minutes them crawled underneath and the right cat is a lot hotter than the left. Also the exhaust on the right side is cold and the left side seems to be warmer. Also on the left side with the warm exhaust I am getting a little exhaust smoke with water dripping. Does this sound like a bad cat on the right side? Thanks for your help!

 

Assuming you also replaced the spark plugs when you did the coils did you happen to notice how dirty or clean the plugs on those cylinders were at the internal end of the plug that fires?

Sounds like you have a blown head gasket between those two cylinders and a cooling port. Do a compression check.

A bad cat will not cause your symptoms or codes.

 

Spark plugs were good and compression was good. Also had the entire wiring harness checked and it was good as well. It's becoming a mystery and very frustrating!

 

If your not losing coolant and you have good compression and injector pulse, you did put a noid light on those cylinders to check for a pulse right? Assuming all that is correct then you must have a vacuum leak.

 

Pulse was good on all cylinders. While I was underneath checking the cats I did notice a small exhaust leak on a weld right after the right cat but I didn't think that would cause my issues. I will check the manifold tomorrow. Thanks for your help!

 

If it was a bad cat, it would do one of two things, either set a code that it was inefficient or you would notice a serious decrease in power. Lean codes and misfires are caused by vacuum leaks and/or ignition break downs, you already ruled out injector pulse and compression so there is nothing else left.

Good luck.

 

One weird thing that I have noticed is, the truck runs better when it's cold than it does when it has warmed up.

 

No vacuum leaks and no ignition breaks! And the mystery continues! This is getting ridiculous!

 

Sounds like it's running rich, excessive fuel pressure is one cause, too many variables to say with out hooking up a scan tool that reads live data.