I drive a 93 cherokee country, 4.0 I6, AT, ~130k. This is a daily driver. Starts great, performs well for about the first 20 minutes of any drive. Then the engine will either bump, momentarily, stall then recover, or stall completely without any electronic loss or reset. The bumps and momentary stalls happen at highway speeds. The complete stall happens at any speed. The tach on the stall erratically moves before obviously falling to 0. No Check Engine Light.
After the complete stalls I am able to pull over, place in park, and then it will start back up. Recently I have had to wait 2-3 minutes until I hear the fuel pump kick on, and then it will fire back up right away.
I originally thought that the heat produced was causing coil separation, so I replaced the ignition coil with no symptom change. I used turn-key diagnostics and received codes 12 and 54. My sources said 12 for recent battery disconnect (b/c ignition coil replacement) and 54 as cam shaft sensor/distributor timing fault. Are these correct?
Research in these forums shows that the crankshaft sensor is the likely culprit, but I have a few thoughts. Whatever is happening seems to be thermally-induced, but typical of the accounts on these forums the crankshaft sensor completely fails so that he engine cannot be re-started. Also, if it is thermally induced, it should take more than the 2-3 minutes to cool enough to reset.
My proposed course of action according to cost/time/ease:
Cam Shaft Sensor & clean distributor
Is this a good course of action? Or should I just jump straight to Crankshaft Sensor?
Of course, my jeep is losing oil, because jeep. No drip, some is probably being burned and I have a light coat on top of the valve cover, most likely coming from a bad seal on the fill cap. I just hope that oil isnít getting somewhere it isnít supposed to be, and causing problems. This seems unlikely though.