engine shut down / restart all within 1/2 second

Topic: engine shut down / restart all within 1/2 second (Read 1112 times) previous topic - next topic

engine shut down / restart all within 1/2 second

May 19, 2025, 02:44:52 PM

This thread serves as my resurection of solving a **VERY*** old problem with my 1990 ford bronco 351 full size.
Recently i got a call from someone i met 10 years ago when i randomly stopped by someones house,, and gave them one of my many Foxthuderbirdcougarforum buisness cards. He had a MKVII HO 5.0 1991

so i finally found someone who has the very exact same problem as me on my bronco,, his mkvii is doing the same thing.

symptom........................
while driving my bronco the engine will shut down and come back on in a flash of less than a second. in a stick shift on my bronco,, this is very very violent and you see and feel the nose drop and pop back up,, so fast my human reaction to let off the gas pedal is not even present.. so ,, when it recovers,, im still the same depth into the gas which makes recovery just as voilent.
In the other guys situation with the MKVIII,, he has an aod so t he vent is somewhat buffered and masked..

We both see our tac decending towards zero but recovery is so fast it gets back to work perfectly fine.

I have my speculations now on may directions i can go to troubleshoot but... i am here now asking if anyone has this issue and what solved it. in my case i have no code that points to this ,, thinking its so quick the eec doesnt log it in continuous or on demand codes.

thoughts?

Re: engine shut down / restart all within 1/2 second

Reply #1 – May 19, 2025, 03:04:34 PM

My first '84 ended up having the infamous first-year EEC-IV processor cut-out. It did just that...cut out for a split second, then the car came back on (3.8L V8/C-5 transmission). Not real fun when turning at an intersection. The car had an extended warranty and it more than paid for itself...EGR, TPS, distributor, TFI module, etc. were all replaced. Think they did the EEC relay also. Finally they gave in and got a new EEC-IV processor and that finally did the trick.

So maybe something in the EEC itself? A lot of times the capacitors go, as there are lots of services that will recap them now.

Otherwise I'm all for the ignition switch or the TFI replacement and go from there. It could be a ground issue somewhere also...like the block to firewall, something like that. It sounds kinda major so you'd think it would be kinda easy to find but I know how sneaky Fords can be, especially with 1980s wiring...

Re: engine shut down / restart all within 1/2 second

Reply #2 – May 19, 2025, 03:14:46 PM

yeah eric,, and being a MKVII, im sure its power hogging / frying contacts in the ign sw. in my bronco though,, its pretty basic.

Re: engine shut down / restart all within 1/2 second

Reply #3 – May 20, 2025, 08:37:38 AM

I had a distributor begin to seize in a 351W ('79 TBird) that did some wonky similar stuff once or twice before it seized and took out the cam gears. Could this be a change in timing to cause this affect rather than the motor actually stalling for a moment?

Re: engine shut down / restart all within 1/2 second

Reply #4 – May 20, 2025, 01:39:22 PM

i agree it can,, in this case though no signs on his MKVII. on my bronco though,, i guess i could check since it is a box store replacement dizzy from like 3 years ago...

Re: engine shut down / restart all within 1/2 second

Reply #5 – May 20, 2025, 04:05:45 PM

Also, in my '79 bird, Ford had that great idea of using nylon teeth for the timing gears with the timing chain to reduce noise. Great until it slips a tooth.......

Re: engine shut down / restart all within 1/2 second

Reply #6 – May 21, 2025, 11:29:21 AM

Mikey................. oh yeah,,,,,,,,,,,, you think?
this was my first major failure ever,, 375kmiles
go to min 5

https://www.youtube.com/watch?v=SjVRYqL4dXU