Help! My 86 Bronco II won't stay running!!!

Ask technical questions about your Ford Bronco II here. Technical write-ups on your axle swaps, engine swaps, chop tops, etc. are encouraged.
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scene red
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Help! My 86 Bronco II won't stay running!!!

Post by scene red » Sat Jun 13, 2009 10:37 pm

Hi. I'm new to this forum but I've been searching posts for a long time. Here's my deal: I have an '86 BII with a 2.9. I've had it for over a year. This past winter, it started running really rough when it got cold (40 or below - approximately). It would jerk/buck like no other until it was good and warmed up. If it was really cold (20 or below) it would take even longer for it to stop doing it. Anyway, that was winter and we are now almost into summer. Now, I will get in it and try to start it up and here's what happens: it will fire up and run for anywhere from a few seconds to a few minutes. All of a sudden, it dies. Just like that. It usually will start up if I let it sit for a few minutes or if I am sitting in it and punch the gas pedal just as the RPM is going down I sometimes can save it from dying out. Anyway, I've been letting it thoroughly warm up to attempt to avoid this (which I find ridiculous in 75+ degree weather but, hey, whatever works.) The other day I was running late for work (I drive 60 miles one-way for work in my BII) and I pretty much put the key in and left. I was not even two miles from my house going about 45-50 mph and all of a sudden my RPM dips low (around 1,500 RPM) goes back to what it was at, keeps going for another 10 seconds and then dies out. I try to start it up and it cranks but doesn't start. I wait about 10 minutes, try and start it up and it starts up fine. After that, no problem. Today, I get in it to start it up for the first time and it will not start up at all. It's still cranking over but it won't start. I let it sit for a few hours, try and start it again and it ran for a second and then died out again. That's where I stand right now. Like I said, I was having trouble with it in the winter and I think the problem I have now is somehow related to the "jerky" problem I was having in the winter. The following parts were replaced to attempt to fix that problem - spark plugs, plug wires, distributor cap, PCV valve, TFI ignition module, BOTH fuel pumps, and one relay switch (the exact name escapes me right now.) Also had a fuel injector treatment done. None of this really fixed it but the weather warmed up and that solved the problem - for now. If anyone has any advice/suggestions i would really, really appreciate it. I know it has to be something simple but I'm afraid if I keep putting it through what I have to just to get it started (repeatedly cranking the engine) I'm only going to do more damage. Thanks!

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Ranger Dave
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Re: Help! My 86 Bronco II won't stay running!!!

Post by Ranger Dave » Sun Jun 14, 2009 4:59 am

change the fuel filter

scene red
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Re: Help! My 86 Bronco II won't stay running!!!

Post by scene red » Sun Jun 14, 2009 11:08 am

Ranger Dave, thanks so much for the quick response.
I forgot to mention the fuel filter has been replaced (about 4 months ago). Sorry. So many parts replaced in a small amount of time. UPDATE: Last night, after reading some related posts on this handy website, I reset my inertia switch to see if that would help - It didn't. Got in my Bronco II this morning. It started up fine for a minute, then died. I let it sit for a few, got back in and tried to start. Started right up. Also, I think the switch I mentioned last post that I couldn't remember was a fuel pump relay switch. Do you think it could be a short somewhere? Also, my dad was over the other day. He mentioned it could possibly be something called a "fast idle solenoid" or something like that. I have been on several auto parts websites and none even mention a part by that name. Does a BII have this part or is it perhaps integrated into another sensor/switch/relay? One last thing possibly worth menitioning. My glove compartment light went out the other day, followed by my horn and now whenever I try to honk my horn it just makes a *click* noise from under the dash. I think the horn relay just went out and I don't think that has anything to do with my starting problem. Like I said, just thought it might be worth mentioning.

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Ranger Dave
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Re: Help! My 86 Bronco II won't stay running!!!

Post by Ranger Dave » Sun Jun 14, 2009 12:33 pm

you changed the filter in the black plastic canister??? do you have access to another B2/Ranger for the copmuter?

scene red
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Re: Help! My 86 Bronco II won't stay running!!!

Post by scene red » Sun Jun 14, 2009 4:48 pm

Yes, it was the one on the frame underneath. I have a 1985 Bronco II I have for parts. It was running when I bought it but I just needed it for the transmission. Anyway, it has a carbureted 2.8 V6 in it. Can I use the computer out of that?

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Ranger Dave
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Re: Help! My 86 Bronco II won't stay running!!!

Post by Ranger Dave » Sun Jun 14, 2009 5:13 pm

nope

kunzelman
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Re: Help! My 86 Bronco II won't stay running!!!

Post by kunzelman » Wed Jun 17, 2009 9:47 am

Try changing the idle air control valve it is located on the throttle body on the left hand side as you are looking at the engine .

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Ranger Dave
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Re: Help! My 86 Bronco II won't stay running!!!

Post by Ranger Dave » Wed Jun 17, 2009 2:25 pm

kunzelman wrote:Try changing the idle air control valve it is located on the throttle body on the left hand side as you are looking at the engine .
its located on the upper intake behind the TB on the pass side. and the engine will run with out that

DBrown
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Re: Help! My 86 Bronco II won't stay running!!!

Post by DBrown » Wed Jun 17, 2009 7:18 pm

EGR valve?

have you pulled codes?
71 Bronco - twin sticked, full width, 2" lift, wristed arm, lots of rust...

http://www.catalystcycles.com

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clem
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Re: Help! My 86 Bronco II won't stay running!!!

Post by clem » Thu Jun 18, 2009 5:47 pm

I call temp sensor! I would pull codes first, no point throwing parts at it. My second thought would be the coil. :canada: :redneck:
'87 bII d44,9",np435/205and a 302 ( on hold)
'73 vw bug
'70 vw camper van
'98 jeep tj
2010 ranger
'56 international s110

scene red
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Re: Help! My 86 Bronco II won't stay running!!!

Post by scene red » Fri Jul 17, 2009 11:27 pm

All right. Thanks to all who've offered their suggestions thus far. Sorry I haven't updated for a while. SO... I have had my B-II at a mechanic's for, oh, about 4 1/2 weeks so far. The first diagnosis led my mechanic to determine the engine is losing spark and he thought the EEC-Relay was the culprit so he replaced it. He thought that fixed it and it went four days without a problem, then it started doing the same thing again. He thinks this narrows it down to one of two things: the distributor or the computer. This week (Monday) he replaced the distributor and told me that ever since then, it has started up perfectly every time. He has been starting the Bronco, on average, about 20 times a day. He said on Wednesday that if it was still starting fine that he would give it back to me on Thursday. I haven't heard anything since which leads me to believe that it is probably still giving him trouble. I'm going to be really disappointed if I have to by a computer for it and that still doesn't solve the problem. I guess this post isn't really to pose any new questions but really to a.)update those of you that have been cool enough to offer your advice, and b.)vent my frustrations. That's all I have for now.

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clem
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Re: Help! My 86 Bronco II won't stay running!!!

Post by clem » Sat Jul 18, 2009 6:15 am

By letting us know what was wrong, we learn too. Thanks for the update.
'87 bII d44,9",np435/205and a 302 ( on hold)
'73 vw bug
'70 vw camper van
'98 jeep tj
2010 ranger
'56 international s110

joshua9295
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Re: Help! My 86 Bronco II won't stay running!!!

Post by joshua9295 » Wed Jul 22, 2009 10:15 pm

i have had the same problem with my 89 b2 i put plugs wire cap button new fuel filter new sensor under the dist. finally broke down for some odd reason an pulled the lower intake off an the gasket was ripped an twisted sorta in the back next to where the dist goes in... sadly idk if it runs yet or not im havin a heck of a time tryin to get it back in time thanks for some un wanted help they got my dist all out of whack an now i cant get the timin back :(

scene red
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Re: Help! My 86 Bronco II won't stay running!!!

Post by scene red » Wed Jul 29, 2009 9:27 pm

All right, folks. Thanks again for all your input. I got my Bronco II back from the shop a few days after my last post. Turns out it was still starting fine the whole time my mechanic had it (after replacing the distributor.)He just held on to it a few days longer than expected. So I have had it back for just over a week now and so far so good. It has started up just fine every time! I've probably put at least 600 miles on it this week, including a trip to the mountains, without any noticeable problems. I'll update if anything new happens, but (knock on wood) hopefully this did the trick.

goodolboy
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Re: Help! My 86 Bronco II won't stay running!!!

Post by goodolboy » Thu Dec 20, 2018 11:51 pm

By replacing the distributor your mechanic took care of a couple possibilities, but my money would be on the ignition control module itself having been bad. It MIGHT have been the internal pickup sensor inside the distributor, but the external ICM going bad was a VERY common issue for Ford during the years when they mounted the module on the distributor-one that was exacerbated if the distributor was mounted in a place that could not rapidly shed heat. On the other hand it makes finding a new replacement very easy.

I've personally had several mid through late '80's Ford and Mercury vehicles do the same thing as you'd been describing.
In 3 separate vehicles from that era it was the ignition control module. All 3 had the ICM mounted directly on the distributor, with a thin layer of dielectric compound between the parts.

The key points to remember are that the engine will nearly always be running just fine until it dies suddenly, there is no coughing or bucking, nothing fuel-related helps because the spark is COMPLETELY gone, and it won't even half-way restart until it cools off, then it runs just fine again.

A fourth similar instance turned out to be the throttle position sensor. In both the case of teh ICM's and the TPS, the part would eventually get hot enough and completely stop working, and then work perfectly once it had cooled down enough.
Depending on the weather, the distributor's location, the vehicle load, and driving conditions, (stop and go vs highway) it could take a few minutes or a very a long time for the problem to show up, but once it does anywhere between 15 minutes and about a half an hour will generally be long enough for it cool off.

My 1987 Ford-5.0L with the bad TPS was especially frustrating because in that particular case the problem would not show up until I'd intentionally STOPPED the engine. Then tried to REstart it. I could drive that vehicle for 2+ hours with no problem, (I was delivering papers at the time) but if I shut it off and didn't restart it within a minute or so "heat soak" would get it too hot, and I'd have a 20 minute wait. Once I'd figured out what it was, (but before I replaced it), I started carrying a spare key and would let it run while I did quick errands. (That car had a big radiator, trans and power steering coolers, and a good cooling fan.)

For those who are interested, the quick and dirty way to test for and either confirm or eliminate both the TPS and the ICM (testing for each separately of course) is with ON ENGINE hot/cold testing.

You start and run the engine (while near a source of water or ice) and let it run until the ignition cuts out.
Then run cold water directly over the part or put a bag of ice around it. If the engine starts when you've sufficiently cooled ONLY the part and the immediate area around it, you've found the culprit. To double check it, repeat the process.

Better ICM's-those with a lifetime warranty can cost nearly as much as a complete, ready-to-mount distributor in some cases.
(MY 1986 2.9L 4WD Auto B2 was such a case.)
Don't EVER be tempted to get a CHEAP, SHORT WARRANTY ICM (or complete distributor replacement without a lifetime warranty) for a Ford engine of that era with a distributor mounted ICU, if you intend to keep the vehicle long-term. That way, after replacing the part, if it happens AGAIN, at least you can then return the bad one and get the NEXT one free.

By the way, any 1986 B2 with automatic will benefit from additional trans cooling-and the early Explorer cooler works with small amount of effort. Every little bit helps that trans.

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