I have a 99 cherokee 4.0 , I was driving about 40 and it just died instantly. We checked it at the coil with a screwdriver and it seemed to be getting no spark, I keep a spare crank position sensor so I put it in and now I have very very weak spark from the coil. so weak that it will not jump more than 15 or 20 thousanths. And it would never come close to firing a sparkplug (I also believe that i had this same spark before I changed the ckps but it was so weak that I didnt notice it until now) I then got excided and bought a new coil and put in on thinking that was the weak spark problem, but I still have the same exact sorry spark that I had before. I do not have a code reader and the only mechanic within 70 miles that does wants 100 dollars to read the codes, and hes an idiot, (maybe even bigger than me)
my questions are
1. I know a lot of shade tree parts changers like to change the cam position sensor in the distributer, If it is faulty would it give weak spark, or no spark at all.
2. I also am beginning to wonder about the pcm, I know it is usually not the problem but what else could it be
3. Are there any voltage check I can make on the pcm or coil?

 

"1. I know a lot of shade tree parts changers like to change the cam position sensor in the distributer, If it is faulty would it give weak spark, or no spark at all.
2. I also am beginning to wonder about the pcm, I know it is usually not the problem but what else could it be
3. Are there any voltage check I can make on the pcm or coil?"

AFAIK its cheap, might as well change it to be sure, I think it would give weak or no spark..
PCM should be fine..
Take your distributor cap off and see what the cap and rotor look like also...