got the cat replaced, check engine light is still on, so i went and had the codes read, cylinder 3,5,and 6 misfire...pulls those plugs and they were blacker than ****. pulled the rest of the plugs for the hell of it, all black. checked the wires, cap and rotor, all fine, checked the coil, fine as well. put new plugs in check engine light goes off, ran fine for about 30 minutes then check engine light comes back and the truck is driving like **** again. So, next thing to check is...what? im thinking check the timing, if thats fine, im gonna go buy an engine gasket kit and replace all the gaskets. thoughts, comments, concerns?

 

If the plugs are black it is running too rich. Do they smell like gas when you pull them out? I think they are probably getting gas fouled, because in 30 minutes new plugs could become fouled. I'd look into the fuel system before I tore down a motor and replaced all the gaskets.

 

fuel system? such as, pump, injectors, lines?....that could timing related correct?

 

alright, i checked my codes...CE code 21...o2 sensor...how can i check which one is bad? exhaust shop does this for free i hope?

 

did you reset your computer? if not try that. if your cat was giving you problems then the motor will adapt to the best driving conditions that it can, now that it's working fine again, it'll need to re-adapt. disconnect the battery for ~5 minutes or so and then run it and see how it does.

with it running that rich, you should also replace the o2 sensor because it's probably plugged up. you can try cleaning it with a electronic parts cleaner FROM an auto parts store (no residue). I do that to mine and it helps alot.

 

yeah i did reset the computer after i replaced the plugs...CE light went off...and then came back on 30 minutes later....is it running rich b/c of the o2 sensor possibly being bad or is running rich for another reason? i thought black plugs meant oil was getting in?

 

Black plugs usually mean it's running rich...white plugs for running lean.

I agree with Steve, replace the o2 sensor. Running rich can plug up & even destroy an o2 sensor. You can try cleaning it first, but if it has a lot of miles on it, you may just wanna replace it.

 

On my M3 & truck, I have no problem spraying them with the elect parts cleaner. it fixes problems... example: my pcm was throwing a code for a cat inefficency... cleaned both o2's & problem is gone. btw, mpg went up a little bit as well.

 

I just went through that all. I had a misfire on cyl 5,6 and 8. I have the 360. I went through everything, new cat, new plugs, wires, and cap, and finally went to the injectors.. The 3 were clogged, so i put a full set of injectors in. It runs great now, but the injectors from dodge are about 85 a peice.. My cost from dodge were still like 60 ea, But it fixed my problem, and on the 360, they were relatively easy to get to. I found out by pulling a good one and switching it with a bad one.. If it doesnt switch your miss you can put them back in, But i would put new rubber o-rings on them before u do so to prevent any leaks.

 

Black or wet plugs is usually too much fuel, oil in there, or lack of fire in the hole. Oil will not usually attack that many cylinders at once.

Not to jack the thread but was wondering. Do our injectors have one hole or multiple spray holes. My dad replaced his on a deisel and had several holes plugged on each injector.