99 Ranger: Engine cuts out randomly, NO codes, NO MIL

The only thing I can think of is a power failure at the computer(lose connection or overheating).

Truck is low usage, only 33K miles in 9 years, all in hot climates, and is probably dying from "dry rot" of hoses, bushings, and... wiring? Engine will die at any RPM or loading. Tachometer drops to zero, even though momentum and manual tranny are obviously keeping engine revved. Does that indicate ignition cut-out vs. fuel failure? After key-off, will usually re-start after 30secs to several minutes. PCM spits out no codes, does not light MIL. (Could it be the FoMoCo built-in ANTI-THEFT system? Is that feature within the PCM?) PS: OBD-II scanner, when booting up, says "RUNNING OBD-II SYSTEM TESTS..." then it says "ALL SUPPORTED TESTS ARE NOT COMPLETE" before advancing to the usual menus. Bad sign? Any insights? ______________________________________________________

The first thing I would suspect is the ignition module (or TFI). It is subject to intermittent failure when heated, and it is the source of the pulses which drive the tach and the distributor.

Good luck.

Rodan.

"Rodan" wrote in news:hzSEj.101$Xl2.74@trndny01:

Thanks, that's a good insight and likely suspect, but could that occur withOUT triggering an OBD-II code? The PCM seems to be pretty "well wired" to ignition issues. It once detected a specific cylinder misfiring, and sure enough, that plug's electrode had separated deep inside the ceramic, and came right out with the boot when I gave it a tug.

"Ripcord" wrote in news:ZPREj.24947$rC6.3795 @bignews4.bellsouth.net:

Day-um, that's one massive harness. It might explain no code too, though I've had the reader hooked up when it happens, and no indication of re-boot... OTOH, I'd better disco the battery, and see if there actually *IS* any indication of when the PCM loses power completely, and does a cold-start and re-learn...??? Hmmm... embrace the learning experience... ;')

Any ideas WHERE to probe with a meter to check power or GROUND? (Although I assume PCM is well-grounded via its chassis bolted directly to body, etc...? ) Guess I should dive in, pull harness, and clean both male and female connectors with contact cleaner, Gold-wipes, etc. Truck has been in both DUSTY (AZ) and HUMID (FL) locales.

Thanks, I'll report back...

snipped-for-privacy@webtv.net (Nick Smith) wrote in news: snipped-for-privacy@storefull-3357.bay.webtv.net:

Does the fuel pump have some sort of overload shutoff protection? Wouldn't the PCM sense/control that, just like KOEO prime?

I replaced the fuel filter about 7 months/1K miles ago... although with such a low-use vehicle, gunky gas IS a danger... I still have the original filter... was going to open it up with a hacksaw or Dremel... never got around to it... I'm MOTIVATED NOW!

But...

a) I don't have a fuel pressure gauge, but pressing the Schrader valve on the fuel rail releases quite a nice geyser, even with key OFF. But truck is worth keeping, so I think I'll drop a few sea shells for a gauge kit... make sure the pressure is high enough, and doesn't fluctuate...busy weekend.

b) Does the PCM have no way to sense and REPORT fuel starvation? That's the stumper here, NO codes... except the occasional P0401 (INsufficient EGR flow), even though EGR itself is fine, I need to check the vacuum hose that actuates it. Is that an engine killer?... doubt it.

Nick, thanks for the feedback... I'll report back.

On Fri, 21 Mar 2008 09:31:08 +0000, fixizin rearranged some electrons to say:

Check for a loose battery cable, or a bad ground connection to the frame.

On Fri, 21 Mar 2008 17:50:05 +0000, Rodan rearranged some electrons to say:

Ford stopped using TFI's in the mid 90's, I think.

david wrote in news:47e4e090$0$30692$ snipped-for-privacy@roadrunner.com:

Granted, but there's still some analagous part in the ignition system that signals RPMs to the tachometer... seems like a good place to start the bug hunt... if it EVER stops raining.

fixizin wrote in news:Xns9A68382B4FC12fixizinyahoocom@216.77.188.18:

SOLVED! Turned out to be the DPFE (Differential Pressure Feedback EGR) sensor! It's up-top and easy to replace. Dang, that's the second "emissions" component that's left me dead on the side of the road (IAC earlier). Puppy runs much better since it's no longer TOO LEAN.

Kind of embarrassed I didn't figure it out myself, but my Lexus insider hooked me up with a Ford insider, and it was no mystery to him, lol. Now on to replace ALL my vacuum hoses.

He also checked out my fuel tank and entire fuel loop--all clear, no GUNK. Today's sealed systems w/ charcoal cannisters do the J-O-B. So leaving the truck sit with 1/4 tank no problem with condensation, and not enough time for fuel to "go bad". (Still gotta Dremel open the old fuel filter...)

Turns out DPFE failure WAS related to the P0401 code, as the DPFE is the main determinant of how far to open the EGR. But the bugger was that it SELDOM spit out the P0401, and NEVER spit it out during a "fainting" episode. It might die 10 or more times before kicking out a code or lighting the MIL. So much for useful codes for the DIY amateur from the EEC-V/PCM.

Thanks to everyone for sharing your FoMoCo experiences and insights!