My '88 4.0 XJ seems to have one cylinder missing at startup after sitting overnight. If it just continued to miss, I would be able to find out what is causing it, but when I get the engine up to 2k rpm it stops and then runs perfectly fine.

It has done this exact same thing for the last couple weeks. At 2000 rpm exactly, it stops missing and then runs fine.

I took all the plugs out to see if they were fouled or looking out of the ordinary and they all seem fine. I can't find anything else out of the ordinary..

Anyone else have a similar issue?

Thanks for any ideas!

 

Did this stymy ya'll? I don't know why 2000 rpm is the magic number...

 

Can you determine which cylinder is missing, quickly before it warms up? Pull the plug wires or injector plugs one by one to narrow it down?
I'd look closely at everything associated with that cylinder. Perhaps swap the injector, the plug, try a different wire and/or cap. See if the problem moves with the part. A compression or vacuum test might be interesting too, at least rule out a valve issue.

 

Mine does the same exact thing. When you start it up in the morning not always but most of the time it has a rhythmic hollow miss that is clearly coming from one cylinder. Hit the gas the miss immediately disappears. Runs great drives great just idles like pooh. No clue why. I have done a full tune up, run a good injector cleaner and it still persists. My next course of action is to get an IR gun and let it idle and see which hole is cold. From there I'll check compression and ignition components. I have 284K so it wouldn't surprise me in the slightest if I had low compression on one cylinder causing this.

 

Sounds like a case of bad injectors to me. If they're original an upgrade before they start leaking and cause a fire would be wise!

However it could be anything really... An actual tuneup might help.

 

Good possibility.

Programbo has the 746 Volvo injectors which work great.