Hey guys,

Trying to get some help for a friend of mine that is having some continual problems.

Shortly, if not immediately, after swapping out his clutch and flywheel he began to have problems with his Z throwing a code for his Crank Position Sensor and running poorly. The sensor was tested with a multi meter per the service manuals testing procedure and was indeed bad. He replaced it with a brand new one, only to find the Z doing the same thing. Throwing a few CPS codes and even an IAT (Intake Air Temperate) code.

After some reading here on the forums and the fact that there were some members having TPS sensors replaced after throwing CPS codes, we decided to rule that out. We swapped his TPS for my completely functional TPS and same thing.

One thing that I think may be probable is that the flywheel was not torqued down to the correct specs. I know that it was torqued down to OEM flywheel specs, which I know for a fact is wrong for my JWT aluminum flywheel. He does not have the JWT, but another aluminum flywheel of a different brand (not sure of brand).

When I installed my JWT flywheel, it was torqued down in three steps. First was 24 ft lbs, followed by 90 ft lbs, and then the bolts were removed. Thread lock was added and they were retorqued to 93-95 ft lbs with thread lock.

I am not 100% sure, but I believe the first torque spec of 24 just evenly aligned the flywheel and the second 90 ft lb pressed it in. Then the 3rd and final with thread lock added just really seated it in there for good.

On his flywheel, they just installed it and torqued it down once to the OEM torque spec, which is around 70-75 ft lbs. Obviously this is way different then what I did and I am sure, not per the instructions included with his aluminum flywheel.

Is it possible that since the CPS reads off of the timing notches in the flywheel, that due to the incorrect torque spec, the timing is not correctly picked up by the CPS sensor?

I don't know if a difference in torque specs would be enough to allow the flywheel to be that far off, but this did start after they swapped it!

The following are the some symptoms of what the Z is doing:

*Throwing code for Crank Position Sensor (continual)

*Throwing code for Intake Air Sensor (only did this once or twice)

*Extremely hard to start. Sometimes taking between 5 to 10 seconds of cranking to start

*Running poorly (at WOT it has surges in power and even momentarily cuts out at around 5000 RPMs)

*When driven normally, the tach jumps a bit through the band as if it’s sticking and catching up (I believe this ties directly in with the whole improperly installed flywheel). When the tack is jumping the car feels fine and is not exhibiting the behavior that the tack would lead you to believe.


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Improper torque won't cause the problems he is seeing unless there's something between the flywheel and the crank shaft causing the sensor to no longer align with the timing ring. BUT, if that was the case he'd have noticed the vibration problems that would have caused long ago.

The best thing to do is to examine the flwheel's timing ring for bent or damaged teeth (you can see it through the small black removable cover that is directly opposite the starter, on the LH side of the upper oil pan). Then measure the voltage at the sensor with an analog multimeter while turning the motor over by hand and watching the multimeter to make sure it spikes as the teeth pass the sensor.

He's definately got crank sensor problems, classic symptoms.

Fred

 

Fred,

Thanks for the informative response. I will definitely point these things out to him.