cats. I had the same problem with a 3 valve expy and it is was the cats....

 

cats r expensive how do they check them front & back 02 senors ?

 

If you pulled codes that say lack of Oxygen sensor switching that whatever sensor it pulled the code for (bank 1 or bank 2 or both) is no good and needs replaced. To test it you need to watch the voltage with a scan tool.

Cats, if plugged, will cause missfires and will get worse the longer you drive.

Paying someone that knows what they are doing fix it is cheaper then you throwing parts at it and hoping.

 

it pulled codes on both banks, my brother inlaw is a mechanic & we r going for a ride tomm to test I like working on these my self I am a tool & die maker & very mechanical I know how to take stuff apart so I will do everything myself saves a ton of money even if I have to replace every sensor then I know there all good.. The cats I will do my self can get both sides factory oem parts , I have a good auto store, they will be just under 500 bucks pipes & all just un bolt & bolt new ones on..

 

Maybe pull the cats and try it? Sorry mine was under warranty and they replaced heads and all sensors before they figured out it was cats.

 

You could cut the cats off, install delete pipes , and have them tuned out. That would probably be the cheapest. You could get aftermarket high flow cats for a reasonable price if you want to keep them. I would still get them tuned out though.

http://performance-curve.com/thunder...-metallic.aspx

 

Just got back & cats r fine fuel pressure is fine, misfire still in # 5 cyl which I think it has a insert in it & it is leaking cause plug had anti seize blown up on it, I will check it after dinner & go from there oh there is no such thing as a high flow cat a cat is a cat just diff design no hp improvement did a lot of reading on them.... worse case sinario I have to pull head to fix!!!

 

have you run a compression test on #5?

 

Im trying got to get the right connector to fit in plug hole .....

 

Sorry to hear I recommend a time sert to fix it right.

 

Never seen a stripped out plug hole on a 5.4 3V.

 

Still waiting for a connector for the comp tester, dont have the one to fit the 5.4 yet, what should I see when looking down the plug hole just the threads & open kole after that ????

 

sorry to hear what I dont have a striped plug hole ? thought it might have a sert in it allready but it dont ....

 

Okay you state that it is leaking I say sorry to hear as it isn't a simple fix and for your information if a cat lets more air thru it how is it not a higher flowing cat(hence high flowing cat name that is used)? I'll troll on just tried to help good luck..

 

OK there high flow, what I read about them is that they are not high performance no hp gain, just saying that is what I read on a big write up on them... not trying to be a ****, when I said leak I thought anti seize was making it past the plugs up on the resistor part, still havnt done a comp test cause I cant find the right size thread to go into the cyl.. will try tommorrow after work, so sick of this truck running like this has no power cant even pass anybody hopefully I dont have to rebuild my motor but I may...