1. Fuel injector blacks and blues

    I have a 154K mile 1988 Cherokee 2-Dr, 4.0L I-6, auto trans, 4WD that my wife bought new. I have kept it mechanically maintained myself, mainly for icy/snowy Oklahoma winter day's commute and as a beater. About a year ago it developed a sudden urge to barely run, belching tremendous amounts of black soot while it does. Enough soot, in fact to completely turn a garage into a contamination zone within a few seconds. In disgust, I parked it. Now, I have decided to try to resurrect it, since winter is coming again. I started it yesterday and it still will make your garage look like a coal mine if it is left to run more than a few seconds. Time doesn't heal ALL wounds, I guess. It seems to me that some enrichening curcuit in the fuel injection logically is at fault, but I don't want to just start replacing parts until I stumble onto the fix. There are no trouble codes displayed. Anyone know of or had this happen to you and have a suggestion for a fix?

  2. Re: Fuel injector blacks and blues

    Check the MAP sensor, especially the small plastic tube that connects the MAP to the bottom of the TB. The plastic tube gets old and brittle and breaks easy. When it breaks the motor will barley run, really rich.
    There are two holes in the rubber stopper near the passengers side bottom of the TB for the MAP vacuum tube. One is a blind hole, the other geos through the side of the TB, careful which you plug into with the vacuum line.

  3. #3

    Re: Fuel injector blacks and blues

    Thanks for the tip. I checked that line and found that not only had the plastic line cracked, but the rubber plug into the TB had fallen completely out, probably from a backfire or something. Can't believe I see something so obvious! I fixed the line, plugged it back in and she runs just fine again.
    Thanks again!

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