I've got a 1998 Ranger 4.0. And it is running extremely rich. This might be a little long, but I want to include every detail leading up to this issue that me and my mechanic cannot figure out.
I should mention here and now, through all this, ZERO codes were thrown, and everything checks out to the computer from my understanding. ALSO, the truck has a brand new pcm, few months prior to this, the old one wouldn't read the o2 sensors, and all this may have something to do with the wiring there. But the new computer reads them just fine, and they also check out, so.
September 1st, I got ready to go 1300 miles to Colorado for vacation and was supposed to leave the next day. I got off work, got in the truck, started it up, and it had a little rough idle. I drove it to the gas station, all was fine. I let it idle while I was in the station, and i go back out, and black smoke was pouring out the exhaust, horrid idle and all, I immediately shut it off. I checked everything I could with my eyes, nothing, other than coolant leaking out the side of the block, which it has done for about a year now, never got to it. Vacation canceled! I drove it back to my work, and the next morning, I have a friend come tow it for me to my mechanic. We got there. We start it up, black smoke turning to white over time. HEAD GASKET right!? Idk, but I told my mechanic to change out the head gasket while he's at it, oh, and rebuild the whole darn thing including the transmission! 2 months later, everything is put back together, thousands in new parts, oversize bearings, new pistons, rings, pushrods etc. You get the point. First start, rough, as expected. But it didn't go away. Black smoke pouring out the exasut. When you drive it, it drives and runs like it just came off the lot. When its idling, its pouring gas in the cylinders, fouling out the new plugs.
It has brand new injectors as part of this job. So it can't be the injectors, since it was doing the same thing with the old ones. Something is telling the pcm to run in a rich condition, I really have no clue. What we do know, the ect sensor checks out, the pcm is from my understanding, working properly BUT there is a chance it isn't. My mechanic is dead set on this issue NOT being the pcm, so were going to pass it up for the time being, and figure out what else could possibly cause this. Although, I have talked to a certified ford tech, and he swears up and down, it's the pcm, but my mechanic doesn't think so. I want to say it's the pcm but I also want to trust my mechanic. He was a gm mechanic for decades and a backyard mechanic for another few decades, and he has never once been wrong with any of mine or my families vehicles.
We both don't know exactly what can cause this. I will be going over to help him in the morning to try and figure this out.
So, what should I check? Or replace? Or beat with a hammer?
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