88 4.0 troubles

[Essayons]

I just found this forum, and hope you guys can help.

My 88 will sputter and backfire through the throttle body when it is under load, warmed up (190+) between 1200-2100 rpms. This problem is intermittant and seems to have no pattern other than what I listed, although some days it will seem to do it more and some days very seldom.

I have replaced the CPS, TPS, and swapped the MAP, no luck. It also has new plugs, wires, and dist cap and rotor. Anyone got any ideas? Also his jeep seems like when it hits @ 3000 rpm like it gets a sudden boost of power it didn't have before, this is my first auto XJ so I am not sure if that is just the way it is with an auto or another symptom of my problem.

I look foward to contributing and sharing on this site now that I ahve found it, if I can get this darn stumble out of my engine!

[Eagle]

How's the oxygen sensor, and how's the catalytic converter?

[Essayons]

Probably my next two things to check. I am figuring the cat is probably ok because thsi problem is so intermittant and it is fine at higher speeds.

[Eagle]

A clogged cat would cause loss of power especially at higher speed, so the next thing to check would probably be the O2 sensor.

[eric91xj]

whoa, i just posted a bit earlier with pretty much the same problem on my '91. i've had this problem for a while and finally decided its time to do something about it. I too and gonna take out the old voltemeter tomorrow and check my 02 sensor. If that is fine i'd guess possibly a worn out cam or a collapsed lifter not letting one of the exhaust valves open up and shooting the exhaust back up into the intake.

eric

[Ron Hyslop]

You might check the distributor intalled correctly. My 87 was installed one tooth off.

[Essayons]

O2 Sensor it was, purrs like a kitten now!