crank sensor

[zjorvis97]

So last week i broke down at a gas station. After spending 2 hours trying to figure out why my jeep would start, but would still turn over, i gave up. I had it towed to some place in Jersey since thats where i was. $700 later i get a new crank sensor and new ignition coil. Jeep now runs, great, but i went from 17 MPG to 8.5MPG on the highway. Can anyone tell me what would make this happen? It the 5.2 318 motor. I have manualy reset the compter and it went to 10, which still isn't normal.

[kirksjeep]

I doubt the crank position sensor would change the MPG since it just sends a signal to the computer for timimg.  As long as it is installed in the correct position it should have no effect on mileage.

I would look into the ignition coil.  Try pulling all the spark plugs and seeing if some are burning richer then the others.  If so the "new" ignition coil might not be the right one. 

Also it seems strage that the coil and the CPS would both go up at the same time.  The fact that the Jeep wouldn't start would make me think the CPS was bad (also a know XJ problem).  Did you have any Check Engine Lights?