intermittent miss

[outlander]

Searched but nothing matched the title of this post.....
I have a miss that only happens once and a while.It doesn't matter if it's hot or cold.Sometimes it runs perfect and then out of the blue it starts to miss at low rpms and usually clears up when it reaches higher rpms but sometimes it'll run like it's only firing on 5 cylinders until I take my foot off the gas then reapply it the miss goes away.Any thoughts?

89 xj fresh 4.0, 5 speed.

 

[Samuryan]

possible CPS

 

[outlander]

Its new from the dealer......

 

[Samuryan]

did you check the plugs and wires?

 

[xjtrailrider]

Check the grounds to the engine block and intake manifold. Take them loose and clean them at both ends then re-attach.

 

[outlander]

Plugs are good and the wires have about 3000 miles on them.I went for the cheap ones so I'll probably replace them with some good 8mm wires just to be sure.Pretty sure the grounds are good because I had them all loose when I replaced the motor in december....but it wouldn't hurt to double check.The iac is disconnected right now because it was causing a high,unsteady idle,I wonder if that is causing this?I don't see how that would matter.

Thanks for the advice.
Anything else anyone can think of?

 

[90xj06]

if you replace the aic dont got the one the computer says at autozone there is one from i think holley that is identical but cheaper.

 

[otto]

Make sure you don't have vacuum leaks and the EGR valve and gasket are good.

 

[outlander]

No vac leaks and the egr is plugged off(the right way)...

 

[gian]

Any more ideas?

 

[RichP]

My 98XJ and the TJ both develop misses every few thousand miles, a bottle of Chevron Techron fuel system cleaner usually clears it right up for a few weeks. Then once a year the TB's get the full treatment.