MichiganCherokee

So my 2001 XJ has always had a miss since I bought it back in October. It has been cylinder #2.
Since then I've replaced the plugs with Champions gap set to. 035, coil rail replaced. TPS replaced, coolant temp sensor replaced. Ran a can of Mopar CCC thru it.
I also swapped out a set of 784 injectors with new filters caps and o-rings. Tried multiple injectors on #2 thinking one might be staying open. No change.
Had the dealership check it out. They're results:
Computer checked out good.
Fuel pressure good.
Sensors all good.
Only misses at idle.
Compression is 160-165(this is awesome for having 162k)
Oil pressure is always around 40-50psi.
Lifters are all in spec.

They were not able to check for weak springs. They are thinking a bad exhaust valve getting stuck or not rotating properly.

I have already planned on swapping the 0331 head with a Clearwater Head which will be ordered next Friday.
Does 160-165psi compression seem right for 162k? I'm not complaining.
Can anyone think of anything else?
O2 sensors and CPS also checked out good. Its been idling rough for the 6 months I've had it.

tjwalker

Is this a misfire that turns on the check engine light/sets a code? You certainly have addressed the usual suspects! Is it ALWAYS on cylinder #2? Every time?

160-165 sounds a little high for compression (spec is 120-150 with no more than a 30 psi variation) but what you are looking for is uniformity of readings between all cylinders. And there can be some variation between gauges and how the test is performed. So you're good there.

It is possible that the head is the culprit. And replacing the factory 0331 head with a Clearwater head is really never a bad idea because of the bad habit of cracking on some (not all) 0331 heads. Especially good idea if you plan on hanging onto your XJ.

Good luck and keep us updated.

MichiganCherokee

I think the previous owner may have pulled the CEL bulb cause its never turned on. Yet I've plugged in my scanner multiple times and got codes.
Yeah two cylinders were 160, one 162 one 161 and two 165. Does burn any oil. They checked the lifters thinking a possible worn lobe but all that checked out in spec.

MichiganCherokee

Doesn't burn any oil**

tjwalker

If memory serves me correctly, you should be able to verify if the CEL light is working as it should flash on momentarily when you turn your key to the ON position.

MichiganCherokee

Oh yeah, last week driving home from work I couldn't go over 40mph because it was running so rough and shaking the steering wheel so hard. Next day it was fine but still really rough at idle, fluctuates from 750-1000rpm at idle.

bbojarzin

Could be a crack in the header, has the misfiring gotten worse over time?

MichiganCherokee

Yeah slightly over time. Its an 01 not sure if those had the issue like the older models. I did check down where the two headers meet into one just by the flange and saw no cracks.