89 xj cuts out at full throttle?

This is my dads xj. 89 xj, 4.0 auto, 200,000 miles (rebuilt motor at 193,000 miles about 7 months ago)

The jeep will idle fine and drives fine if you ease into the gas pedal, but if you step on it, it cuts out and acts like it is flooding out, even backfires.

New: champion spark plugs, wires, cap and rotor (at rebuild), new fuel pump and filter (at rebuild), CPS sensor (1 month ago), MAP sensor (3 weeks ago), Oxygen sensors (3 weeks ago), IAC (at rebuild)

Checked: TPS (today, we replaced with new one and adjusted to .83 ratio, no change, so put old one back on and adjusted to .83 ratio), Coil (replaced with new one and made no difference, so put old one back on) CTS (unplugged today and made no difference) EGR valve (tested manually, seemed fine) Fuel pressure is 31 psi and raises to 39 psi when stepping on the gas), spark plugs looked good, cap and rotor looked fine, have cleaned almost all electrical connections and checked all vacuum lines for clogs or leaks, unplugged each injector individually and noticed a change in rpms, plugged all back in.

Any ideas? Oh yeah, this all started about a month ago, with slight hesitation and a buck every now and then and has progressed to this.

grn98xj said:

CTS (unplugged today and made no difference)

Click to expand...

I don't think that is going to show you if the CTS is ok or not. If possible, get an ohm reading off a new one and compare that to the reading on the engine part (cold of course). I had one go bad on an Aerostar and it was reading completely open, whereas the new part had a readable resistance out of the box. Open, and/or high resistance equates to a cold engine, which will cause too much fuel to be released by the injectors.
Also, you can try removing the relays over the coil, clean all their plug surfaces, and maybe swap them around to see if there is any improvement.
That's all I have for now...

I do not know that much about all these sensors, unplugging it was something that I had read on one of the forums. We can test and get an ohm reading to see if that might be bad.

Thanks for the idea

it might not be a sensor at all. when you go to wot the engine leans to one side and a wire may be loosing contact. it could be your mat sensor may be malfunctioning.

It will actually start cutting out at about half throttle, but I guess it could be something like that. It seems more like a bad sensor. What kind of test is there for the MAT sensor?