Stuttering XJ

I have a 96 XJ, 4.0, AT, 168K. Several weeks ago and suddenly, it began stuttering when I slowed down to a stop. I check the codes. It was reading P0171 (system lean) and P0300 (random multiple misfire) and P0301 (cylinder 1 misfire) and P0304 (cylinder 4 misfire).

I began by changing, plugs, wires, rotor, cap. That did not do the trick. I then changed the fuel filter, thinking it may be clogged. Still no change.
I checked the codes. It was reading P0171 (system lean) and P0300 (random multiple misfire). I then changed the downstream O2 sensor. Still no change. I then changed the upstream O2 sensor. Still no change.

By this time it was idling pretty rough some of the time and idling normally at others. It began cutting off at stop lights and stop signs.

I took the throttle body assembly off, sensors and all, removed the sensors and carb cleaned the piss out of the trottle body. I then cleaned all of the sensors.

It now idles much better, but begins stuttering again as soon as I give it gas or sometimes put it in gear giving the engine a load.

Any thoughts, war stories or advice would be appreciated.

Jason Price

The first thing to check is the fuel pressure. All the parts in the world wont make it run if it has low pressure OR low volume. Search both, they are in here.

Thanks. That was next on my list. Just can't find the time to work on it for more than 30 minutes. I'll let you know.

that happ on my TJ, and it was the intake manifold gasket.



:repair:

It was the fuel pump. Only had 17 or 18psi pressure. I changed the pump and it runs like new.

Thanks to all for comments.