This is sort of a continuation of the issue that I mentioned in a previous thread, but the check engine light in my jeep goes off and on depending on how I drive. The engine will be running perfectly fine, then I'll drive agressively and push the engine to 3000-4000 RPM on for example a long up hill on the freeway, the engine will start running rough at idle. Then I turn it off, turn it back on and 20-30 seconds later the check engine light comes on. I also noticed that when it's running rough the exhaust seems to come out of the tailpipe in puffs, instead of normally as usual. I drive gently and a few days later the check engine light goes off and it runs normal again, then the cycle starts over. It's also getting abnormally bad gas milage too, around 12mpg. Any ideas? Thanks.

 

uh... pull the code??

http://www.go.jeep-xj.info/HowtoECUcodes.htm

 

Wasn't completely sure you could do that without a reader. thanks.

 

The codes that came up are 12 and 43. 43 came up twice, is there any significance to that? I also took off the distributor cap and inspected it, there appears to be a lot of grey powderish stuff caked onto the inside of the cap and rotor. Is this normal? I'm thinking of replacing the wireset, cap & rotor and see if it helps. Anyone have any insight to what could be going on? I'm pretty inexperienced when it comes to working on cars.

 

1991 - 1997 model OBD-I Trouble Codes:

Code 12: Battery voltage to PCM disconnected within last 50 key-on cycles.

Code 43: Misfire; Misfire in one or more cylinders.