'88 BII Randomly Dies

My 2.9 efi 88 BII will run great for hours (like on a 2 hour drive from city, to highway, to mountain road - from sun to snow). Then, randomly and unexpectedly -maybe after driving for only 30 minutes or maybe after driving for an hour or more, maybe going 65mph or maybe 20mph, maybe with temp gauge in first 1/4 or maybe in top 1/4, it suddenly feels like the gas pedal doesn't work. Lights, power steering, tach (slowly going down) are all up and running, but the car decelerates and the gas pedal does nothing. Right as it comes to a stop, it shuts down.

I've had a very similar problem in past years, but the difference then was that it would always start right back up immediately. That was cured when my mechanic replaced the TFI about 14 months ago.

Now, it dies in a similarly unexpected way, but does NOT start right up (though it smoothly turns over repeatedly and "almost" starts). Now, it won't start for maybe 45 minutes and 10 tries, or so, then, suddenly, will start just fine. My mechanic just put in a new TFI, but it did it again two more times last week - so randomly and sporadically, of course, that he can't recreate it.

One thing I think I noticed the last time, right before it finally started (after 10 tries and 45 minutes) was a small clunk apparenly under the dash, but possibly behind the firewall, when I turned the key - then it started right up.

Since it needs this 45 minute rest period, I thought of things heating and cooling. The engine temp, however, doesn't seem to have an effect. But, I realized that it has been happending when I've been running the heater/defrost full blast to keep the windows from fogging. My BII has an EB body and a very shallow dash area - heater ducts are missing and I know it gets very hot under the dash - like if you pull out the ash tray to grab a coin in there, you can barely pick them up. So, in both recent cases, the under-dash temp was very high and had cooled off after waiting for 45 minutes.

Does this ring any bells for anyone? Could he have got a bad new (not junk yard) TFI right off the bat? Is there a brand or particular module anyone would recomend as being more reliable - and good for city and highway driving (vs. for rock/mud rigs).

Is there any fuel or other relay that could get hot from my modified cabin heater, fail when hot, then work fine for hours when cooled off? Some things are in different places in my EB/BII, but mostly I find them about where they would be in a stock BII.

Thanks a million!

Lot of info there, and honestly dont have the attention span to read it all, but I would have the fuel pressure regulator looked at. May also be electrical (battery or alt).

sounds like the tfi is getting too hot. are u using aftermarkter or oem ford parts? if its been doing it and fixes it everytime u replace the tfi might wanna do the tfi relocation mod in the tech section. just a thought. doesnt really sound like a fuel problem, it would do it all the time

First thing to always check for intermittent faults is the wiring. Look for shorted burnt or melted wires or connectors pull your connectors apart and inspect/clean and put a little dielectric grease to protect from corrosion. Check the computer for any codes stored in the memory sometimes they will point you in the right direction. Especially any wires close to the exhaust system O-2 sensors and such.

It's hard to diagnose anything when we don't know why it wont run.

An engine needs three things to run. Fuel, Spark, and Air. (Provided everything else is fine)

When your truck dies, see if you can find out what is missing. Air wont be the problem, so it has to either be not getting Fuel or not getting Spark.

Take some starting fluid with you, and when your truck dies, spray some starting fluid in the intake and try to start it. If it does not start, then the component you are missing is Spark, which would indicate an overheated TFI. (Among a number of other things, but the TFI is the most likely culprit, given your explanation)

I'm curious if your mechanic put on a new or used TFI. If he got it new, it should have come with some grease. If used, and he didn't regrease it, that could be the problem.

Making your TFI 'remote mount' is easy and will cure any over heating problems with it.