I recently (2 weeks ago) bought a 1999 Chevrolet Express Explorer conversion (150 000 miles). So when the engine has gotten warm and Im idling in Drive the engine occasionally shakes, like once every 5 seconds or so. Its like a misfire but I have not gotten any fault codes indicating misfires. I checked the spark plug wires, they look fine. The shakes seem to occur only when in Drive, or at least with less force when the gear is in N or P. I don’t ever notice anything when driving.

The AC recently stopped functioning (the compressor stopped its on-off cycle [which used to be kinda loud]). The temp gauge is stuck in 75 C (Im guessing default mode) and I did get a fault code saying P0141 (Oxygen O2 Sensor Heater Circuit Malfunction [Bank1, Sensor2]).

Might all these things be interrelated? Any ideas? Im mostly worried about the shakes the engine makes every now and then.

 

Check for vacuum leaks, that could cause your shaking. The compressor on-off cycling indicates being low on freon. When it stops doing this it indicates much lower on freon. You are getting a code for the 02 sensor. If you have not previously changed the 02 sensor with 150,000 miles on the truck, it is past due. Change the sensor anyway, it needs it.

 

I got the AC working with a new clutch relay. Only the AC does not blow very cold at all, it is colder than without it but just barely. The entire system was apparently (according to previous owner) overhauled and most things replaced with new in 2010.