99 4.0 rich, black smoke p0171 code
Okay, here we go. Jeep was having intermittent stalling, especially at speed. Swapped out the CPS and it fixed that problem. At the time I also had a code for the front O2 and the MAP sensor. So I reset the computer and the P0171 code came back. Jeep is using a lot of fuel, there is a lot of black smoke coming out of the exhaust with hard acceleration and it's missing at idle. I had recently changed the MAP sensor so I swapped the old one back in to see if there was a difference, there was none, I ran a 1/4 can of throttle body cleaner through the intake, a bottle of fuel injector cleaner, and reset the PCM. P0171 came back, so I swapped out the front o2 sensor that I changed about 4 months ago and it was black of course. Reset PCM, stomp on gas, still have black smoke.
I checked fuel pressure and it is around 45PSI and seems to stay there when shutting off engine. Right now I'm leaning towards faulty or leaky injectors. Let me know if you guys think this is the direction I should take (gonna check plugs when I get a chance to try and narrow things down)... I also banged on the cat and heard no rattling, it is not discolored and there is a strong exhaust (doesn't seem clogged). Jeep has 185k miles so don't know if the rings are bad but I could probably borrow a compression test gauge and do a wet comp. test. But I'm pretty busy and my girl needs the WJ for work too.
-Some maintenance done in the last year:
Put in a new tranny a year ago and have changed many many things since then. No fuses are blowing, electrical connectors seem OK. Fresh oil change with rotella syn, pure one oil filter, spectre air filter, new IAC, TPS, MAP, CPS, plugs, front o2, fuel pump, fuel filter, let the injectors sit in carb cleaner overnight just in case and put new o-rings. Checked and replaced any bad vacuum hoses, checked and cleaned all electrical/sensor connections and checked for corrosion. The list goes on and on, radiator, condensor, starter...
Anyway help a brotha out! What could it be now?? A couple of the sensors are cheap off ebay but voltage readings were fine, no codes, and aside from maybe TPS I don't see what could be causing it.
So in order of what I think could be wrong
Exhaust leak (I checked obvious places but will inspect further)
What sayeth the forum?