Need help with trouble codes, engine misfire

[live24wheel]

I'll give ya a quick rundown on the XJ. Its a 1997 with a 4.0 and a Manual. About a year ago it overheated and warped the head. We got a head job done on it and and all put back together. Right after that the clutch went out and in the process of replacing it we yanked the wires out of the CPS. Got that all done and replaced the CPS. It ran and still runs perfectly fine but has had the check engine light on since we redid everything. We got the codes pulled, which I will list below. They mainly all have to do with misfires except one says it is not getting a Crank position signal at the CPS and that one has me stumped, well they all do because it runs perfectly fine. As far as the head goes, they had to mill it back flat and said they had to take a pretty good amount off to get it back flat. The only time it "misses" is if your in say 3rd at about 3,000 rpm and stomp the throttle it has a hesitation or "miss" and then takes off like it should. Im wondering if it had something to do with compression numbers rising or if it messed with the timing because they milled the head and maybe that is causing it. Any input would really be appreciated, I will post this up on NAXJA and see if anyone over there knows as well. Here are the codes...

P0300 - Multiple Cylinder Mis-fire
P0301 - CYLINDER #1 MISFIRE
P0302 - CYLINDER #2 MISFIRE
P0303 - CYLINDER #3 MISFIRE
P0304 - CYLINDER #4 MISFIRE
P0305 - CYLINDER #5 MISFIRE
P0306 - CYLINDER #6 MISFIRE
P0320 - No RPM Signal to PCM (Crankshaft Position Sensor Signal to JTEC) - A CKP signal has not been detected at the PCM.

Thanks,
Tom

[SilverXJ]

I would start by checking the wiring between the CPS and PCM. Also, check the distributor indexing. Since the head was so warped they probably did a valve job as well, which, depending on the quality of the job, could have brought the valve stems up. That combines with the surfacing could be causing a preload issue.

[Don H Jr]

If it doesn't happen to be all that complicated stuff; maybe the computer hasn't been reset since you tore out the CPS and put it back in, and it's just remembering the real deal at that time. Try pulling off the positive batt cable and grounding it out for 30 seconds to release the info into the ozone layer; then put the cable back on, go to ignition and turn key on position but don't try and start engine. Reach over and pull the headlight switch on and off twice. Turn off key.
Now you are running on program orignally in computer, at least on OBD1 it works this way. It forgets the temp stuff stored in computer diagnostics department of computer and takes 50 starts to reprogram itself completely with real time data.

don jr

[offroadaz]

Hi, sorry to bump an old thread

But was this ever fixed? Im having the same problem on my TJ. Getting the p0300-306 along with the p0320

Ive replaced the pcm, tps ,fuel pump, coil rail, spark plugs and had a shop look at it

wondering what you found out

[Don H Jr]

A mouse.

Srry, kidding.

Don H. Jr