88 Bronco II - Intermittently Stops Running
 

I have a 1988 Bronco II with 2.9 EFI engine, 5 speed manual,4WD, all original with 160,000 miles. For the last two months the engine stops running intermittently. Usually after waiting 5-10 minutes, it starts and runs fine, and most of the time does not give my any more problems the rest of the day. Although sometimes it will stop several times within a couple of miles and other time runs fine for over a week. It does this in wet or dry weather, cold or hot days, up hill, down hill, on curves, straight roads, after driving 2 miles or 20 miles. Once it stopped while sitting at a traffic light. I have change the fuel filter, have gas pressure at the manifold, changed the distrubitor, pickup, ICM, cap, rotor, plugs, wires, and both relays on the fender by the air filter. Also, while it ususally restarts after 5 or 10 minutes, it has let me sit for over 30 minutes several time and once for over an hour. There is no preamble to it stopping, the engine just dies and after a while it starts and runs fine. Any input would be greatly apprciated.

Any codes in the computer (some causes of stalling/no start will leave codes in the computer's memory)?
Can you tell why it stalls/won't start? No spark? No fuel pressure?

I just got a code reader to check that, and yes there is spark and fuel pressure

Gee, where did you check for a spark because it sounds as though it's likely to be the ignition module on the distributor that's got an intermittent (probably temperature-related) problem?

My BII is getting close to 160,000 miles and, in fact, I just ordered one of these modules to keep as a spare as this seems to be a really common fault at around this mileage. It's scheduled to arrive tomorrow.

I changed the ICM as well as the entire distributor and pickup

If it has spark and fuel pressure, then --
1) Is the fuel pressure correct (40 psig KOEO)?
2) Are the fuel injectors firing?
3) Is the spark at approximately the right time?
4) Is the spark getting to all/most cylinders?
5) Do the cylinders have compression?
6) Something blocking the air intake?
7) Did you get a chance to pull codes?

I had a similar problem on my 88 Bronco II, mine turned out to be the fuel pump inertia switch. This switch is located in the floor board on the passenger side. The problem wasn't the switch but the electrical connection is in a positon that someones foot can rest against it causing it to have a bad connection and thus shutting off the fuel pumps. When the engines shuts off reach over and jiggle the wires to see if it may be your problem. I replaced the switch and the wires with one from a 1987 Taurus, which is located in the trunk. I also made a sheet metal guard to keep feet off of the wiring. This solved my problem, I hope it will help you.

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The fuel pump relay could also be intermittent. All my codes were ok and the other checks were good. I finally took it to the Ford dealer when it died and had a diagnostic done on it. They found the relay was intermittent.