[jfrabat]

OK, guys; after undoing the TB swap because of all the engine problems that I was having, I decided to take some measurements (fuel pressure and vacuum). Please help me diagnose the symptoms of my jeep!

Symptoms
When engine is first started, it "lops" for a couple of cycles, then turns on the CHECK ENGINE light and the throttle smooths out. When the air conditioner compressor comes on, the idle drops dramatically, and the Jeep stalls or comes close to it.

I tried "reading" the code, and it looks like 12, 13, 55; but the spacing is so odd, that I am not sure that is what I am reading (I got a short video in case anyone is interested in reading it for me; just le me know your e-mail address and I will send it - it's about 330Kb). In any case, I got a OBD1 code reader compatible with Jeep arriving tomorow, so that should clear one part of the problem up!

The next symptom is that the engine will not rev past 4,000 RPMs. Once it reaches that figure, it drops to about 3,500 RPMs, and continues in that cycle until you stop giving it gas. It does this both in gear and in neutral.

With the engine hot, when you give it gas, the engine stalls. You have to stop giving it gas and the engine comes back to life (sometimes!). To accelarate, you have to SLOOOOOWLY bring the RPMs up.

Measurements

I decided to measure fuel pressure and vacuum, as these sounded like the most obvious places to find a problem (other than the ECU, which I cannot yet read).

The vacuum readings were OK, with the idle measurement being fairly steady at 17 in/Hg, and going up to 20 in/Hg (again, steady) at 2,000 RPMs. As I understand it, this is indicative of a good functioning engine.

The fuel readings, however, were a totally different subject. Instead of the pressure coming up to 31 PSI as it should when the ignition is turned on, it only came up to 25, and the pressure dropped slowly to 20 within a minute (the ignition was still on). When the engine was turned on, the pressure needle started dancing wbetween 42 and 45 PSI. If I revved up the engine, the pressure would steady up at 44, then drop to 42 when I stoped giving it gas, then it would start dancing again. When I shut off the engine, the rpessure slowly dropped to 26, and then it continued dropping, but at a slow rate.

Any thoughts on this?

All your kind help is much appreciated!

Felipe