Geekmedic

Greetings
Need help. Putting together a 99 XJ. Block is from the 99, head is from a 00. Were having trouble getting/keeping it running. Thinking we need an OEM cam position sensor.
Need help sourcing one.

TrailerTrash

Any codes?

I am assuming it is a 4.0L

Geekmedic

Yes it is a 4.0
I believe we are having trouble getting a signal with a proper scan tool.

BlueRidgeMark

???

Why would you use the worst head ever put on a Cherokee 4.0???

Geekmedic

We had the 99 with bad valves. The 00 was a Grand Cherokee with a good head, and free.

BlueRidgeMark

It's always helpful to provide complete and accurate info.

dave1123

In the long run, you're going to wish you repaired the valves in your original head because that 0331 head is a failure waiting to happen.

Dave51

What does that mean?

Why do you think that?

bluejeep2001

As far as I know the 0331 head is not directly interchangeable with the exhaust pipes on a 99..I don't think it bolts up properly. I know the ports are different sizes compared to the 99. you might have induced an exhaust leak or something. If your 99 has a distributor then there should be no issues stemming from just a head replacement other than physical damage during swapover You might have also not gotten the distributor indexed properly, thus the bad readings

Ralph77

I always wondered about that.
The exhaust ports are bigger on the '99 head.
So smaller on the 0331 head.
So is it possible to not have an exhaust leak using a '99 exhaust manifold on a 0331 head?
But I am with BlueRidgeMark on this one.
But not just cause it probably is the worst head ever.
Would hate to find out that trying to use a '99 exhaust manifold with a 0331 head could be not so cut and dry.
Even if it was free.

Geekmedic

Using a real mechanic's scan tool, not a cheap Amazon OBDII scanner

I really don't know to much about this swap. The vehicle is being built by a very capable teenager (he's rebuilt other motors, and vehicles). I'm here trying to find answers for him.

Dave51

It's still not clear-- is the problem with your real mechanic's scan tool or whatever it is you're trying to analyze? Can you post some images of what you're trying to do (you need to get to 10 posts)?

Why specifically do you (or he) think the cam sensor is bad?

Dave51

Agree knowing that is key, as well as all the observed parameters from their real mechanic's scan tool.

The 0331 head runs with a COP and waste spark system. One wonders if the absence of that results in feeding odd information to PCM (like O2 sensor is seeing a too-rich mix) and injector time is AFU.

bluejeep2001

None of that should matter because he is using his 99 electronics, , they would not know what head is up there. The gaskets are different between 99 and 01 , that may not be his issue . I would suspect a mistimed distributor. have him unplug both 02 sensors...run off factory alternate programming..see what happens...same thing for the water temp signal..unplug it and let it go to factory alternate. See if anything changes

Dave51

Precisely my point. The PCM would be processing data as though an 0620 head were there.

That said, there would most certainly be OBD codes, like an 0172, and it is not clear if there are codes or not.

If there truly aren't any codes, then perhaps it's the CPS, notorious for failing and not generating error codes.

Would be very helpful to see screenshots of their "real mechanic's scan tool" to see why they think it's the cam sensor.