Renix Camshaft Position Sensor?

My Comanche has been taking loner and longer to start it seems. It also will idle great for about the first minute after you start it cold. But then, as the engine warms up the idle drops and gets more rough. Then at about 170F the idle jumps back up and seems to idle ok. When the engine is hot though, the idle is at about 800RPM and every 10 seconds or so there is a rough period in the idle that shakes the whole jeep. The idle speed is also very erratic, fluctuating +-200rpm. I've compeltely removed the throttle body and cleaned everything, check the intake manifold bolts, and checked for vacuume leaks.

Today I disconnected the Camshaft sesnor at the distributor, started it up and it took about the same length of time to start. I also disconected it while the engine was running and nothing happened. I'm thinking the Sync sensor is shot.

Anybody replaced this sensor before? I'm assuming I have to remove the distributor? Can I replace the sensor without messing up the timing of the engine?

What are your TPS values?

TPS reads 4.2V at ECU side.

Assuming you have an automatic that would be close enough. Do you have an analog meter so you can check the TPS through a full throttle sweep?

joe_peters said:

Assuming you have an automatic that would be close enough. Do you have an analog meter so you can check the TPS through a full throttle sweep?

Click to expand...

No I do not, but it reads fine with the throttle closed, so it shouldn't effect my idle right?

Disconnect your TPS harness at the TPS. Key in "ON" position should have 5.0 volts between Pin A(power) and Pin B(ground).

Then reconnect the harness to the TPS and backprobe the weatherguard connector and with the key "ON"and the throttle closed check for .85 volts between Pin C(positive) and Pin B(negative). If you don't have .85 volts adjust the TPS.

Joe is essentially correct - but bear in mind that the provided "reference" voltage that is delivered to the TPS can wander, which is why it gets adjusted. IIRC, you adjust the engine side so that output voltage is 17% of input voltage, after reading the input voltage.

The "sweep test" is something I came up with (others may have as well - but I think I was the first to mention it...) when throttle response would go to Hell at part-throttle. The construction of the sensor lends itself to generating "flat spots" over time - right where you cruise most. That's what you're looking for with the analogue ohmmeter (can't do it with a digital, as there are buffer circuits that delay readings. You need instant response.)

You'll have to pull the distributor to change the camshaft sensor - but it's not that difficult to do. You don't even have to TDC the engine, if you mark everything carefully before and while you pull it apart. The distributor shaft comes out the top, but you have to drive a roll pin out at the bottom to release the drive gear before you can remove the shaft.