F150prerunner

Hey guys, newbie to post but longtime reader. I've also got a 91 f150 5.8 with the same problems. Replaced tumbler(for the hect of it), ign. switch, ign. module,tested coil was good. Finally replaced pick up coil inside dist. got it started. Ran good unless I was on a rough dirt road, then It acted as if there was a short and would cut out. Took it back home to check for loose connections and now I'm right back to square one with no spark. All the new parts only have about 10 miles on them. Just drove down the road and back home. Hopefuuly somebody can help. I love the truck but is seriously pissing me off. I dont have a bunch extra cash to keep replacing parts, you guys have help me out alot on here. I thought i narrowed it down and fixed the problem.The truck ran good until it snowed, drove it once in the snow, now nothing but problems. Thanks in advance.

Just call me Sean

iTrader: (1)

Same deal, check for power at the coil and ICM.

F150prerunner

Sorry should of mentioned that I already have and I do have power to both thats why I replaced the icm and tested the coil. I'm going to pull the dist. to test the pick up coil but just replaced it doesn't even have 10 miles on it.

travisc21

Well, i finally found the problem. Had a bad connection on one of the connectors near the drivers side fender that goes to the icm, and also a bad connection to the coil. It still had power going through it but not enough for the icm.

Since i replaced the distributor my timing is a little off now. I was going to go out and buy a timing light, unless anyone knows a easier way to time it??

Just call me Sean

iTrader: (1)

It doesn't get any easier than a timing light except the probe type that mechanics use.

F150prerunner

Glad you found your problem. I'm still searching for mine. Checked every single conn. in the engine comp., traced wire looms with no such luck. I guess I'll replace the pick up coil again, thats what got it running before. But the next ? is what is making them go out so fast. This one only has less than 10 miles on it.At least its not my DD but i really like driving this truck. I dont like it sitting in the driveway not running. Any help would be appriciated(sp). Thanks

travisc21

That sounds like what mine was doing. It would occasionally pop off but then other times no spark at all. My icm still had power but not enough which is what threw me off. Try putting the key to run, and check the power to the icm while wiggling all any any wires coming from it. When i did that on the icm, the light would flicker and get brighter and dimmer. It really sounds like you have a short somewhere.

Just thought id help i know how frustrating it is when ya cant figure it out.

F150prerunner

I tested power to icm and coil, I have good constant power, wiggled, messed with all conn. and wires with no dimming of light at all. Tried turning truck over messing with all wires and conn. with no change. I'm stumped. I've narrowed it down to either the computer or a faulty pick up coil. As mentioned before i replaced the pickup coil and got it running, but only for a couple miles. Would it be worth replacing the entire dist.? Is their anything else inside the dist. that would mess up, that i havent replaced? Maybe the metal pickup that works in conjuction with the pickup coil?

Just call me Sean

iTrader: (1)

Sent you a message.