I have a 2000 XJ 4.0 4x4 auto. I had a lifter going out and a crack 0331 head. I replaced the lifters and got a tupy 0331 head to install. Had the valves done, ran great for about a day. I was on the highway at about 70 when it started missing, cel blinking at me. I get it back to the house and I gave a p0306. I checked spark, fuel valves everything and can't get it to stop missing. I replaced the plugs, fuel injector, coil, checked all grounds, did compression check, pulled the head back off and check everything again, I can't make it stop. Can anyone shed some light on this it is driving me mad. It is only cyl 6. Please help.

 

You had a lifter going out....did you check the cam lobes while you had everything apart? If the cam was worn at all, it's a good chance the new lifters wiped out the cam. Also, was the valve lifter preload checked after the TUPY head was installed? If it's back together again, do a compression test and a cylinder leakdown test to determine what is wrong with cylinder #6. If the lifter preload was too tight, you could have burnt a valve.

There's also a possibility you pinched the wire harness where it goes around behind the head and injector #6 isn't working.

 

Everything with the head, including preload, mashed harness and valves has been checked. The collapsed lifter was on cyl 3 not 6, cam is all good. I caught it early.

 

Let's go to the basics. How's the spark on that cylinder? How's the injector?

Never assume coincidence, but never rule it out completely. This might have nothing to do with the head.

 

Spark is nice and strong. Thats whats so confusing, spark is good, fuel is good at the injector, i don't get it.

 

You check if your cam sensor is in phase?

 

Hmm. Compression is good....

Leakdown test? Even though it's a new head, mistakes can be made. Can't rule anything out at this point.

 

What means that? Did you use a noid light to see if the injector is firing?

Consider dead injector driver, or the associated wiring.

 

TTBOMK, that would generate P1391, P0351, P0352 and/or P0353 codes.

 

I'd be curious to see the results of a compression and leakdown test. It can't be the coil since #1 and #6 fire together.

 

I know this is an old thread, but has there been any updated outcome of this? I'm currently going through the same issues