Funky idle...Check me on known probs...

Ok here is the deal. I did some searching, but didnt really come up with an answer. My Jeep is a 94 4.0, auto. I have no mods to the motor except for a 40 series. Lately, the idle has been really lopey... I wouldnt really call it rough...most like its got a mild cam in it. Things Ive done... Full tune up last year. Plugs, wires, cap, rotor, O2, TPS, MAP, fuel pressure regulator, fuel filter (yesterday), filter changes, redid entire CCV system with new parts, and Im sure other stuff I forgot. My know problem right now is a crack in my exhaust manifold in the usual spot..and maybe one up higher on the tubes.

Now..through common sense and what Ive read on here, that crack can mess with the O2 sensor some. Can it cause enough interference that the motor will idle goofy? I also seem to be running alittle rich. The black soot on my fairly new and clean tailpipe clued me into this. In my mind, if the O2 is getting fresh air that its not supposed to, it could be thinking the motor is lean...and might add more fuel.

Any of this sound like Im on the right track? Let me know what you all think. Either way Im going to replace the manifold and fully weld most of the exhaust... So I guess that will tell me for sure.

Justin

No ideas??? Just thought I would bump it once to see if anyone can help. Ill be busy fixing some other stuff, but when i get around to fixing the exhaust Ill let post if it helps the running condition. Until then...any help is appreciated... thanks

Justin

TPS ?? :dunno:

Can you pull codes with the check engine light on a '94? Could be many things. You replaced 02 but how long ago? It could be bad. Thermostat or temp sensor not allowing ECU to use 02 input? Leaky fuel regulator? Have you cleaned intake/throttle-body/IAC recently? Get's pretty sooty in there since gasoline is kept much closer to the intake valves. Needs regular cleaning. Check ground strap - back of head close to firewall. Maybe TPS, how's it shift?

Need to be a very large exhaust leak to mess with 02 me thinks.

Good luck

Are the injectors in good shape? My 93 idled chunky due to the O2 sensor cycling lean/rich.

FUNKYTEE5

Hmmm...some good suggestions. I havent had a check engine light, but I guess I can try to pull codes just in case. The TPS is pretty much new. I replaced all the major sensor when I bought it. Ran great for a long time..now its acting up. It started to act up right after my manifold started leaking bad. Could be coincedence though... When I do my manifold swap and exhaust work Ill probably toss in a new O2 sensor just in case.

It seems to heat up good, and the fan kicks on correctly, so Im assuming the temp senders are all ok. Thermostat is only about 6 months old.

So...the few things Im not sure about are the injectors...and the cleaniness of the throttle body. I do wipe the TB down every so often when Im putzing around under the hood. Its got a new CCV system, and I usually dont have a lot of oil in the TB. Im not exactly sure how to check out the injectors...because Ive never had to before. But, when I have the intake off Ill replace the o-rings and try to figure out how to check the injectors.

Thanks for the ideas...for some reason I never thought to blame the injectors...


Justin