I went to Autozone today and had them put the truck on their obdII handheld and it showed a bad cam position sensor. They do not sell that part, nor does O'Reilly. So, I called the local stealership and they dont sell one either. The stealership parts guy suggested that it was a crank postion sensor and not a cam position sensor. What do you guys think?

The 2.4L and 3.3L equipped 2000 Xterras has them. The sensor is built into the distributor. The Camshaft Position Sensor(CPMS) itself can't be replaced in this instance. The whole distributor must be replaced. That's why the dealer parts system won't show it. But a Nissan parts guy who knows his stuff should know this. I don't know for certain if your 97 HB has the same setup but heres the info I have.

Then this is why it runs rough at an idle up through 2k rpm?

If we had the O.B.D. code we could be more insightful.P0340 or PO335 or a P1code.

just got from a trip to a mechanic who tested the compression on all 4 cylinders....#4 had almost no compression

That's not a good thing to hear. I would have done a leak down test too to find out where the pressure loss is.

Blown head gasketCracked Head - bad rings/pistonbad valve or valves.

A leak down test would tell you where the pressure is going.

Well, the truck doesnt overheat, use ANY oil or A/F, so Im thinking a bad valve....what should I expect to pay for that repair providing the head is good?

Maybe I should just find a KA24DE Turbo JDM engine and build a sleeper.....

I guess Im gonna go somewhere and get a full diagnostic done...Any major franchises to avoid? I havent taken a vehicle to a mechanic in so long I dont have one I "trust".....

I don't who you can take it to in your area.

Strange that the one cylinder showed NO pressure. If you have access to an air compressor and the fittings that thread into the spark plug holes you can do this yourself. Have you ever done or know of anyone who can do a leak down test?

The offending piston should be at DBC or TDC inorder to seal the combustion chamber. Once you connect the air supply you'll know instantly if it's a bad valve because the air will bleed either back through the intake or out the exhaust. There could also be a crack in the head between the valve seats. Then the pressure would just release back into the ports of the head.

But if the head gasket is leaking you would see bubbles coming out at the radiator. (Pull the rad cap before you pressure the engine up).

Then look and listen.

I took her to an import shop who ran a complete diagnostic and found that #4 has no (0) compression due to a bad exhaust valve. this truck only has 98K miles, hows does a valve go bad like that? They want 1K to fix it....$750 of that is labor....

A bad exhaust valve can be caused by several things.

Debris was embedded in the seating surface of the valve. Sand, metal shavings, carbon deposits, etc.

When the seating surfaces get damaged it's just a matter of time before the valve won't seal properly at all. Somtimes the valve can actually burn and melt at the edge from repeated exposure to the combustion cycle. The other thing that can happen is the seat just wears out and the valve can't seal. The price seems fair because the head will need to be rebuilt once they pull it.

Click here to view an example.

Good website on Engine and Head rebuilds

Thanks for the info, it was very informative. I have lucked out, a mechanic friend has offered to R&R the head for $300, and I buy the parts and pay for the head to be rebuilt. Our local O'Reillys has a machine shop that can do the head....