I have a 96 4.0 automatic cherokee. In the last couple weeks she has starting missing a little, thinking it's plugs I changed them out ( still missing )The missing is intermitent some times say in the morning when it's cold ( it's real bad but when it's warmer weather not so much ) When I go up a hill it seems to be worse and level ground not so bad and some times I can drive all day with no issues. I was told it could be the crankshaft postion sensor on the bell housing. Does anyone know or can point me in the right direction as to my issue? Thanks

 

It's not uncommon that moisture in a dist cap can cause trouble when it's cold.
You might check it for condensation some morning. Anyway you would want to rule out trouble with the cap and wires before you worry about sensors and such.

The auto parts should read your codes free, and/or try this ;

1984-1986 w/GM V6-173 are OBD-I (GM control setup.)

1991-1995 are OBD-I (Chrysler)

1996-2001 are OBD-II (Chrysler)

The "Key Tricks"
Older (OBDI) models - Start with the ignition off. Within five seconds, switch the key on, off, on, off, on. ("On" is NOT "Start" and "Off" is NOT "Lock"). The "check engine" light will flash. Count the flashes. Each code is a two digit code, so a (for example) 23 would be FLASH FLASH (pause) FLASH FLASH FLASH (long pause). It will never flash more than 9 times, so watch for those pauses!

Newer (OBDII) models - Put the key into the ignition, push down the odometer reset button, then turn the key to RUN with your finger on the button - and then release the button. The odometer will go through 1111111 through 999999, then display the car's serial number. It will then show the error codes (it might show them starting with P). If this method does not work, try the OBDI method.

 

I just had a friend do a code reading with a code reader and I'm getting no code errors. I will check for condensation in the morning. I did forget to say that it does idle fine with no miss and under acceleration it does'nt miss. thanks for the info

 

Finish your tuneup before moving onto more complex possibilities. Failure to do so can result in the chasing of your tail and the emptying of your wallet.

Fresh plug wires, distributor cap and rotor.

The importance of solid tuneup hardware cannot be overstated.

 

X2. Plugs aren't the only part that goes bad.

If its only under load, though, it sounds like a fuel issue.

 

The instructor, Stan Vermiel, (Yea, coach Dicks brother), in the SRJC program where I got my CA smog license explained this: As combustion cyl pressures rise the voltage needed for the spark to jump rises. If you have condensation, carbon tracks, or another option for the secondary voltage to take, it can show up under acceleration. (or with a weak spark or bad wires, may not make the trip at all).

Counter-intuitive, I'd think the denser mix would make a better conductor

 

sorry i have not gotten back to every one. i"m moving and it's taking all my time. but i did look at my distributor and rotor and found what looked rust . i just flaked it off all the contacts and cleaned the rotor. have not had the time still to try it out but will let every one know the out come . thanks again for all your help guys