91 F350 dies after throttle blip

[theSHERPA]

I have been neglecting the IDI and finally got around to starting her up today. It has been a couple months since I have touched The Sherpa, and I had to jump her to get her started. Let the batteries charge and got her up to operating temperature.

So it idled fine as it got up to temp, but when I blipped the accelerated while parked, up to maybe 2500 rpm, it would miss idle on the way down and die. Started right back up and I was able to replicate over and over. Instead of settling at idle, it would die. If a feathered the accelerator as dropped back towards idle, I could keep it going.

Does this sound like a bad sensor? Never had this issue before.

It was a sunny day in Texas, and maybe 45-50 degrees.

Thanks for any input.


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[79jasper]

No sensor could cause it.
When you hold the throttle, does it run rough or smooth?

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[wwwabbit]

How old is your injection pump? Try some fuel conditioner, mine does that often when it is warm, seems to go away with some fuel conditioner/lube.

 

[david85]

How old is your injection pump? Try some fuel conditioner, mine does that often when it is warm, seems to go away with some fuel conditioner/lube.

^^^What he said. This usually is caused by sticky governor linkage inside the injector pump. Normally the governor has to catch the engine RPM when its dropped to idle the way you are when you feather the accelerator pedal. When it gets sticky, the engine can drop below idle and recover on its own, or in your case, stall. This is why the condition is easily repeated, and the engine still runs if gently returned to curb idle.

I had this happen to me once with my pump before I sent it off to Agnem to have it "moosified". The cure was some Dexron3 automatic transmission fluid in the fuel tank. I dumped about 1 liter in there and the problem gradually went away during the course of 2 hours driving in mild urban stop & go traffic.

Its a combination of age and fuel quality that can cause this but in many cases, is recoverable. I do run stanadyne lubricity supplement but nothing seems to be quite as potent as ATF for a case like this. My pump still worked reliably well over a year after I first had this problem. Having the pump rebuilt was a matter of choice and convenience, rather than necessity. I have no doubt it would have kept on going.