J30 Throttle Position Sensor/Crankshaft Position Sensor

[aerotigger]

I have done a lot of reading on here, but never posted anything. This sight has been a wealth of knowledge so I thought I would give this a try.

I have a '94 J30 that I picked up from my brother as a tinker project. The transmission had stopped shifting into 4th gear. He had it checked out and they indicated that it was the transmission and not the computer. I pulled the transmission, had it rebuilt, and put it back in. The car did great for about 2,000 miles then the transmission started slipping when downshifting from 4th to 3rd. I also noticed a loss of power when the car was warm which my brother later told me was there long before the transmission problem. I took the car to T3 for a diagnostic to double check the transmission and the loss of power. Unfortunately, it was a cooler morning so the car's power was fine. They indicated that there was nothing a new transmission wouldn't cure. I just installed the transmission again after the second rebuild. The car had no power and the shifts seemed even more off than before. It's even difficult to categorize. I had read on here and in my service manual the TPS could be connected and also decided to check the Crankshaft position sensor. I checked the CPS per the service manual which includes removing it turning it slowly and monitoring the output voltages and listening for injectors. It seemed to be functioning correctly so I reinstalled. The TPS varied between 1.1Kohms and 4kohms instead of the 1.7k to 10k the manual indicated. The initial voltage was 0.58 Volts. I replaced the TPS and calibrated it to 0.45 volts with the ohm range exactly per the manual. I decided to take a test drive which ended up with me making it down the street, but no where else. There is no power now, and the engine will not turn over more than 1,000 rpm under load. I reinstalled the old TPS and set up as it was before. Still does the same thing so I put the new one back in. I started to take it back to T3, but these two things seemed straight forward enough to try before I did. Now it would have to be towed which I'd prefer not to do. I noticed the mounting holes on the CPS are slotted. Is the clocking critical? The manual doesn't mention it, but it seems that would play some part in its performance.I'm open to any suggestions someone may have. Thanks!

[Q45tech]

The adjustment slot on CAS [crank postion sensor has at least a 50 degree range] it is critical that it be adjusted with a timing light to within +- [2-3] degrees of spec..............it is the master clock for cpu/ecu.

J30 CAS end shaft [where it fits into cam] wear is common......replacement is the only cure.

[aerotigger]

I thought the description in the infiniti service manual was too brief. I couldn't imagine that the clocking on that sensor wasn't critical (especially since mounting locations are slotted). I put a timing light on it and tried to set the timing. The engine won't even stay running long enough for me to set it. I guess maybe I completely screwed up the sensor this time. I got the car for a learning experience and it has certainly been that. I don't get a check engine light from the sensor, but it looks like the algorithm for setting the fault is pretty loose on that sensor.

Thanks for the help! I'll keep you posted.

[aerotigger]

Oh, just for the record, the car has 317,000 miles on it. So any type of wear item is possible. I do have extremely detailed repair records on the car though.

[aerotigger]

Just to follow up, I installed a new camshaft position sensor. Set the timing and the engine purs great. Just a note, when you start to set the timing make sure to reinstall the intake duct while you do it otherwise the car will run a few seconds and shut off.

The engine seems to have the power it is intended to have. Now to just get the transmission issue resolved.