I got a 95 F250 with a 460 and E4OD Automatic. Recently it began a weird random misfire/stumble. The first time it happened it was idling after driving for about 30 minutes. As it idled it would randomly cut out like it was gonna stall. It would stumble and idle up to about 900-1000 RPM's and idle smooth then do its thing a few more times. Then through out the week it would still sometimes do it. It has new cap, rotor, plugs, wire and now a new coil (thought maybe that was the issue but it still does it). IAC looked a little cruddy so I cleaned it. Vacuum lines have recently been replaced and still in good shape. I also replaced the fuel filter. No codes show at all but when doing the KOER test, it flashed 4 times for a V8 like its supposed too but, when it did its quick flash to rev the engine, the engine stumbled. After that it was like it started its test all over. It did its four flash again as if I turned the key off and restarted it. IT recently began stumbling while driving. If the OD off light is on, it'll go off once it stumbles. Kinda sounds like a electrical issue. I replace the EEC Relay and that didn't fix it. I am gonna change the fuel pump one next. I shook wire and everything trying to see if it would make it stumble and nothing happened. cant make it stumble, it just randomly does it on its own. I cant figure out what else it could be. I thought the IAC but I'm not sure if that would affect it while driving. Anyone else experience anything like this Like I said, no codes (except the 111 one of course) and it never actually stalled. Just stumbles. Any ideas or advice?

 

You didn't mention it but quick test, when you turn the key to "run" (don't start it just turn the key to run and listen for the pump to run, might need a helper near the tank) how long does the fuel pump run before shutting off?

Does it run for say 30 seconds then stop? or does it run continuously and as long as the key is in the "run" position? (again, key on engine off).

You could replace the fuel pump relay but it doesn't sound like its a problem yet at this point.

 

I'm working out the same intermittent stumble on my '94 F350 w/460 and E4OD. I haven't solved it yet but have it narrowed down to possibly the PCM starting to fail.

I removed the PCM and opened it up to inspect. Nothing jumped out really burnt/bad. But the three blue capacitors do show signs of breakdown starting. So I'll probably have it reworked as soon as the truck can be out of service for a few days.

This truck has a new engine and transmission, new distributor, plugs, cap, rotor, wires, etc. I've also tested and replaced almost every sensor on it as well.

No trouble codes other than 111

So you might want to pull the PCM and have a look at it.

Hope the input helps.

John

 

The fuel pump will run for about 1 or 2 seconds as usual. I also forgot to mention the truck has dual tanks and regardless of what tank its on it still does it.

Cleanseeker, I've been fearing the PCM is bad. My old 5.0 in my old truck misfired like hell when it was 50 degrees or colder. Turns out it was the pcm. I soldered new capacitors in and it fixed it.

 

The pump not running continuously doesn't eliminate it as the cause.

Inability to get it to return a proper response, successfully run through the self test does make it suspect.

 

Sounds to me like the PCM Computer is doing a reinitialization over and over.
This does not mean the Computer is bad but you need to fined out why it is doing the reinitialization.

 

I was thinking maybe the pcm connector is corroded. I'll check all that when I pull the pcm out.

 

Or the code readers connection with its port.

Are you using a Innova 3145?

Computer if original and very possible that it is, its 21 years old now so at minimum worth a look see.

The computer in my 95 showed no outward signs of cap leakage when i pulled it, replaced its caps anyway.
I haven't yet as its been mostly a work in progress up till this fall but intend to replace the caps in the 97 I recently bought too. I see it as cheap insurance prevent a damaged board as well as head off potential problems it could cause otherwise.

 

I don't have a code reader. I count the flashes of the check engine light.

 

Start checking grounds and wires for chaffing. If it stumbles regularly at idle, I'd hook a multimeter up to the 5v reference wire on one of the sensors (TPS, MAP, etc...) and see what it does. If it momentarily drops to 0 (or some number significantly below 4.5v), the ECU is either losing power, or the 5v regulator inside the ECU is failing.

 

Well, pulled the computer and opened it up. Inside looks great but I discovered something while pulling it out. It got jammed when it had only about an inch left to come out. After tugging it hard a few times it came out but the back side had an opening. I looked inside the PCM compartment and seen a black computer chip. It appears to be a hypertech chip. I have no clue how they got it on there considering it cant get past the firewall due to it being a tiny bit wider than the hole for the PCM. But, the screws holding the chip to its bracket were very loose along with one of the bracket hold downs missing. I resecured it and shaved the opening so I could put it in as one whole unit. Also cleaned the connector good. It seems like it runs better and doesn't jump around so much on a cold start like it always has. It hasn't "stumbled" for awhile (like a week or more) so I'm wondering if that chip being loose was the cause. I guess I'll find out eventually. I'll add pictures of this chip. I wish I could just remove it but I'm sure I'd have to find the original factory chip? I doubt it adds much power at all.

 

There was no factory chip. There is just a blank plate that goes over the hole.
All that chip does is add a little advance to the distributor and make you run a little high octane fuel.

 

I might just remove it and see how it does then. I hear people had issues with those before

 

It just overrides the Ford factory ROM with their own. It probably raises the shift points a bit, runs a bit more timing, and that's about it. Probably worth 10HP or so.

If that connection became loose or corroded, it could definitely cause issues. Removing the chip will just default to the factory setup.