I have a 97 F350 CC 4X4 7.5 gas E4OD California Emissions OBD2 truck (has the 96 body style).
Recently as I am driving, it will missfire for a half-second, the tach drops to zero then comes right back up. Feels like a gear shift would, as it happens so fast, just kind of bucks for a second. Then goes back to normal operation.
No codes thrown.
I have searched and read other threads with others having the same problem. Lots of suggestions, but nobody ever responds with the thing that fixed the problem.
If I figure it out (with your help) I will leave a final answer so it is there for someone else to search and find.
Any help please. It is not an issue with spark plugs or wires, as the tach drops to zero as it looses its signal. My electrical manual shows the ICU sends the signal to the tach, but might also be the trigger in the distributor?
If you think maybe one of these, any suggestions to determine which one is the culprit?
Thanks

 

Clean or replace the TPS/IAC, check the fuel pressure (it should be around 39PSI replace the filter if needed), clean the throttle body (use throttle body cleaner, no carb cleaner), check or replace the O2 sensor. Finally, you could run Seafoam to clean carbon deposits and see if that helps.

Apart from the afore mentioned, check all the grounds, a loose wire and even a little short could cause those symptoms.

 

Great advice there Encho, but before going too far check for codes. There is a code related to an erratic PIP signal. The PIP, aka stator, is located in the distributor. The output signal triggers the Ignition Control Module (ICM) and PCM to fire the spark plugs. This part is a very common culprit of all kinds of driveability issues and no start conditions. Your symptom of the dropping tach reading leads me to believe I am on the right track at this point. Never underestimate the simple things, as Encho mentioned. A bad ground can fool the best of us......

 

Update on the fix for this problem (in my truck anyway.)
I narrowed it down to either 1) ICU 2) stator 3) aftermarket alarm system.

It was kind of a crap shoot between the three as the problem only occurred randomly with no similar surrounding circumstances like temp, road bumps, heat, ????.
So I guessed that if it was the ICU, the truck would probably totally die instead of miss a beat while running down the road (at different speeds.) and maybe start back up if I was lucky.
Stator - don't know how to test - especially for an intermittent problem.
Alarm system - kind of didn't want to mess with that unless it was absolutely necessary - it is very convenient. but I could see how the immobilizing function could possibly kill power to the engine as with this system everything works with the alarm on - gauges, starter, etc. just the truck won't fire.

I figured that the truck with 190,000+ miles on it - I would start with the stator. Found a factory Ford distributor at a dealer in New Jersey (last factory part one around I was told by Team Ford in Vegas) and had it shipped to me. Cost 100 with shipping. Figured that with 190,000 on it my original might have some bushing wear anyway, so opted for the entire distributor.

Put it in and have had no problems since (couple of weeks.)

I just left this so that if someone else has the same problem and does a search, they might have a place to look at.

 

Thanks for the feedback!

 

Mine seems to have a very slight hesitation when idling and when its cold I have noticed if you turn the steering wheel rather quickly like backing out of the driveway it stalls. Always starts right back up but it has just in the last few months started doing this. I have changed the cap, rotor, and plugs in the last week and stalled again this morning. Any ideas?