Allen Sokos

I have a 1990 f150 and the motor has been acting funny with this cold weather. When the engine gets up to temp the engine will suddenly shut off usually around 1 engine rotation and turn itself back on, triggering the warmup cycle again bringing the rpms up to 1500 and settling back down. It does it more and more when it runs when its warm. Earlier it left me stranded as it shutoff but didnt cycle itself back on. The fuel pump wouldn't stop running and it would crank but wouldnt fire. The fuel pump was running but not shutting off for over 5 minutes. I let it sit for a minute and it started up but it was running poorly, going from 300rpms to 1500 and everything inbetween, smelling rich. I shut it off after 20 seconds of that and waited 5 minutes and it ran fine for a 15 minute drive back home. What the hell is going on, I'm thinking its my ECU, but I dont see anyone having a problem like this anywhere.
This is the video I got of it acting up, when driving it's like it just stops firing for a second. At idle it shoots the rpm's up to 1500.
Video:

midwestbird

Erratic engine behavior has been attributed at times to bad ECUs. My truck started violently bucking and I eventually discovered that my ECU was bad. I had read that the EEC-IV capacitors can eventually leak. When I inspected mine, sure enough I observed what appeared to be a fluid at the base of one of the capacitors. So, I replaced it with a manufactured one and my bucking went away. It might be worth your while to remove the ECU and visually inspect the circuit board.

Steve83

That's the hallmark of failed capacitors. They can be bought locally or ordered, and replaced at home using a common soldering iron. Watch a few YouTube videos, and read this caption:


(phone app link)