86 Bronco II Quitting on Me!

[Mhollis1]

Need your help folks... 86 Bronco II 2.9v6 E.F.I automatic - 94,000 miles. I have had this vehicle since 2013 so I know it pretty well now. Problem I am having is this - once the motor reaches a warm temp ( lets say by the temp gauge needle approaches the O in normal ) the motor begins to surge and stall as if it is not getting fuel or air. This happens quite quickly on Hot /Humid days but still behaves the same in colder climates. Once it begins this phase it will quit and will not start again until it sits for 10 - 15 minutes. After it starts again I can take off and drive on just fine unless I hit stop and go traffic or lights. Once I hit stop and go traffic or lights it will repeat this and quit again. I have talked to several Mechanics / gear heads young and old and those whom have given suggestions I checked/tested to no avail. I replaced the pickup(distributor) and even moved the ignition module off of the distributor and over to the firewall. I replaced the fuel pump relay, idle control, map sensor, both fuel pumps ( yes with remanufactured pumps but note it was doing this before I replaced them), fuel filter, removed the cat, checked fuel pressure it is in spec. , replaced coil on fender by the battery, checked the Inertia switch. I am really at a loss on this. One notable fact it appears that it no longer has the Pep or power that it once did.
Any advice would be greatly appreciated-

 

[Uncle Gump]

The first thing to do would be to actually see if you have spark when the vehicle quits.

 

[FIngerstyler]

Mhollis1 - that problem started on my 1986 EB 4wd automatic 2.9er in March of 2020. I did the same things you did, new distributor, new TCM on distributor, new wires, new coil, all new relays, new relay connectors, new battery, new alternator, new cables all the way, check out the roll over switch by taking it apart works great!, new connectors on both new fuel pumps 3 times each, most all this work was done/diagnosed by ase mechanics, i'm just the researcher, those are all the relevant parts anyhow that have been replaced...the biggest news is that up until today i can't find the answer especially since i have used 8 ECM's in 2 years, all A1 Cardone, 1 MasterPro but that's A1 anyhow, replacing it cured the 18 minute runtime then die but now i get a new ECM and 2 of them have smoked as soon as i start up the car for the first time, the others seem to last and run good and cure those other problems like too rich and lack of pep, but only for a couple of months then they either head in 1 of 2 directions 1) No longer will turn on the fuel pump or 2) No longer will turn either the fuel send unit pump off or the rail pump off. We still keep saying it is a bad ECM so we took a Cardone that was still under it's 1 year warranty and sent it to some company in miami, they supposedly fixed it but we installed it and it does the same thing...won't turn off the rail pump, yes car runs ok for now but not going to drive it like that. Incidently last year we hooked up a pressure gauage and watched it with a steady almost 40psi for 18 minutes then watched it go down to 10 when the time limit was reached and the car stalled in the driveway. I'm taking it back to shop for 10th time this week they are going to once again go thru the wiring and tell me it can only be an ECM issue which i believe but last week i installed a new one and it smoked so i went right back and replaced the older one and it does not get smoked it just keeps the fuel pump running.

 

[Mhollis1]

Mhollis1 - that problem started on my 1986 EB 4wd automatic 2.9er in March of 2020. I did the same things you did, new distributor, new TCM on distributor, new wires, new coil, all new relays, new relay connectors, new battery, new alternator, new cables all the way, check out the roll over switch by taking it apart works great!, new connectors on both new fuel pumps 3 times each, most all this work was done/diagnosed by ase mechanics, i'm just the researcher, those are all the relevant parts anyhow that have been replaced...the biggest news is that up until today i can't find the answer especially since i have used 8 ECM's in 2 years, all A1 Cardone, 1 MasterPro but that's A1 anyhow, replacing it cured the 18 minute runtime then die but now i get a new ECM and 2 of them have smoked as soon as i start up the car for the first time, the others seem to last and run good and cure those other problems like too rich and lack of pep, but only for a couple of months then they either head in 1 of 2 directions 1) No longer will turn on the fuel pump or 2) No longer will turn either the fuel send unit pump off or the rail pump off. We still keep saying it is a bad ECM so we took a Cardone that was still under it's 1 year warranty and sent it to some company in miami, they supposedly fixed it but we installed it and it does the same thing...won't turn off the rail pump, yes car runs ok for now but not going to drive it like that. Incidently last year we hooked up a pressure gauage and watched it with a steady almost 40psi for 18 minutes then watched it go down to 10 when the time limit was reached and the car stalled in the driveway. I'm taking it back to shop for 10th time this week they are going to once again go thru the wiring and tell me it can only be an ECM issue which i believe but last week i installed a new one and it smoked so i went right back and replaced the older one and it does not get smoked it just keeps the fuel pump running.

I am truly at a loss with it. My next step is placing the ignition module somewhere near the radiator fan, it’s over on the fender now but I noticed it is getting Ridiculously hot. Not sure how or why that is but I will take a look at that wiring when I do. If you find anything out please let me know I will do the same.

 

[FIngerstyler]

Yeah i would think your TFI would really not be that hot now condisidering how hot it must get on the distributor position. We did not move the ICM/TFI like all those articles suggest, but the first time we replaced it, would not start. So went and got another one. Now i am going to ask they check that this week. I try to always buy Motocraft or Fomoco parts because of that experience. I also replaced the key switch in the steering module. I think it was the new ECM that got us past the 18 minute run time but now like i said we I get a Cardone reman ECM and it either, 1) burns up in 1 minute of run time 2) works great for ~1 month and stops turning on fuel pumps so it won't run or 3) works great for ~1 month and won't turn off the rail pump or some ECM's won't turn off the fuel send pump.

I have been reading about this for 2 years now, there's plenty of forums talking about it since 2008 maybe. Really can't find a solid answer or their answer was not the solve for my issue. They are calling it "The curst of the B2 or 2.9". I will let you know after this week what they say about mine once again.

 

[FIngerstyler]

Well today after i installed a new 'rod assembly" in the automatic stick shift (maybe the last rod assembly on earth that is correct part) and a new T-shift handle, i unplugged the ECM and turned key to ON not running and the rail pump came on, so that i would think is not and ECM problem but rather a wire issue, fuel pump issue, or relay issue. The relays are new so is the pump. Their going to have to check pump and relays again.

 

[FIngerstyler]

They finally figured the issue of the HP fuel pump on rail staying on...somewhere down the line a mechanic had cut one of the fuel pump relay wires and grounded it right there about 8 inches away from the relay! That explains the ECM's that burn up as soon as they get plugged in, but no explanation whatsoever about the ECM's that don't work correctly but don't burn up. So they found the correct wire and reconnected it, now the fuel pump only comes on when it is supposed to, when you turn the key on it runs for a couple seconds, and of course whenever else it is supposed to run. Now the final issue of when it gets warmed up or hot...it sputters and stalls then won't run until a little cool off for about 30 minutes. I'm not sure how long it will run after than cool off becuase i keep it close to home and it always happens around the corner, i start it, it runs i get home and park it. I noticed the other day the ECM gets really hot, not enough to burn you but if you put your hand on it you want to remove your hand right away. That kind of temp does not sound right, i could expect it to be luke warm but not that hot.

 

[Bronco 2 man]

Sounds electrical to me. Good luck with it

 

[Uncle Gump]

Electronics get hot...

Your run til warm... then quit and won't restart til cool sounds like classic TFI.

 

[FIngerstyler]

Uncle Grump - that's what i keep thinking....i think i told the mechanic that but i don't think they listen. I'm thinking on try to make it run bad again then place some ice on the TFI ICM whatever and see if that cures it. I could buy another ICM but i replaced 1 and still got the same result, i think i bought a MotoCraft and that did not help, other peoples are saying buy the best one that is lifetime warranty. Other peoples have replaced it and did not help either https://www.broncocorral.com/forums/index.php?threads/blasted-tfi-ignition-control-module.121187/

 

[Uncle Gump]

I was going to say... stay away from the cheap replacements.

You did put the heat transfer grease on the module... right?

I'm thinking I'm going to br proactive with mine and remote mount it.

 

[FIngerstyler]

You did put the heat transfer grease on the module... right?

Yes! I can still see that grease if i look very carefully! The thing about remote mount is "why did mine and thousands of others work for about 34 years"? I have all records in a spreadsheet and i see that module being replaced only a couple of times.

 

[Bronco 2 man]

I’m agree with uncle Gump sounds like tfi but ecm getting hot is puzzling!

 

[Uncle Gump]

Made with pride in America?

All I can say is... there are truckloads of really junk parts now days.

 

[JerryC]

They finally figured the issue of the HP fuel pump on rail staying on...somewhere down the line a mechanic had cut one of the fuel pump relay wires and grounded it right there about 8 inches away from the relay! That explains the ECM's that burn up as soon as they get plugged in, but no explanation whatsoever about the ECM's that don't work correctly but don't burn up. So they found the correct wire and reconnected it, now the fuel pump only comes on when it is supposed to, when you turn the key on it runs for a couple seconds, and of course whenever else it is supposed to run. Now the final issue of when it gets warmed up or hot...it sputters and stalls then won't run until a little cool off for about 30 minutes. I'm not sure how long it will run after than cool off becuase i keep it close to home and it always happens around the corner, i start it, it runs i get home and park it. I noticed the other day the ECM gets really hot, not enough to burn you but if you put your hand on it you want to remove your hand right away. That kind of temp does not sound right, i could expect it to be luke warm but not that hot.

Sounds a little like a problem I had years ago. The wires to the HP pump were loose. Actually the female spade connectors got loose somehow. They just opened up a little, crimped them down a little and that fixed it.

Sometimes it would run for hours, sometimes 30 minutes from cold. My guess is the loose connection got hot pulling current through it and expanded, add in some vibration and it lost the connection.

Oh, how loose were they? I went to check the connection and it came off when I touched it. The rubber boot was likely the only thing keeping on.

 

[Mhollis1]

They finally figured the issue of the HP fuel pump on rail staying on...somewhere down the line a mechanic had cut one of the fuel pump relay wires and grounded it right there about 8 inches away from the relay! That explains the ECM's that burn up as soon as they get plugged in, but no explanation whatsoever about the ECM's that don't work correctly but don't burn up. So they found the correct wire and reconnected it, now the fuel pump only comes on when it is supposed to, when you turn the key on it runs for a couple seconds, and of course whenever else it is supposed to run. Now the final issue of when it gets warmed up or hot...it sputters and stalls then won't run until a little cool off for about 30 minutes. I'm not sure how long it will run after than cool off becuase i keep it close to home and it always happens around the corner, i start it, it runs i get home and park it. I noticed the other day the ECM gets really hot, not enough to burn you but if you put your hand on it you want to remove your hand right away. That kind of temp does not sound right, i could expect it to be luke warm but not that hot.

Awesome!… I am now at the point of moving my TFI from the fender (originally on the distributor) to somewhere near the radiator fan to help cool it. It gets hot to the touch and I can’t find anything else as a culprit that I haven’t replaced. Tired of not being able to drive it around town in stop and go traffic. Will be doing that here in the near future and will post the results.

 

[Mhollis1]

Mhollis1 - that problem started on my 1986 EB 4wd automatic 2.9er in March of 2020. I did the same things you did, new distributor, new TCM on distributor, new wires, new coil, all new relays, new relay connectors, new battery, new alternator, new cables all the way, check out the roll over switch by taking it apart works great!, new connectors on both new fuel pumps 3 times each, most all this work was done/diagnosed by ase mechanics, i'm just the researcher, those are all the relevant parts anyhow that have been replaced...the biggest news is that up until today i can't find the answer especially since i have used 8 ECM's in 2 years, all A1 Cardone, 1 MasterPro but that's A1 anyhow, replacing it cured the 18 minute runtime then die but now i get a new ECM and 2 of them have smoked as soon as i start up the car for the first time, the others seem to last and run good and cure those other problems like too rich and lack of pep, but only for a couple of months then they either head in 1 of 2 directions 1) No longer will turn on the fuel pump or 2) No longer will turn either the fuel send unit pump off or the rail pump off. We still keep saying it is a bad ECM so we took a Cardone that was still under it's 1 year warranty and sent it to some company in miami, they supposedly fixed it but we installed it and it does the same thing...won't turn off the rail pump, yes car runs ok for now but not going to drive it like that. Incidently last year we hooked up a pressure gauage and watched it with a steady almost 40psi for 18 minutes then watched it go down to 10 when the time limit was reached and the car stalled in the driveway. I'm taking it back to shop for 10th time this week they are going to once again go thru the wiring and tell me it can only be an ECM issue which i believe but last week i installed a new one and it smoked so i went right back and replaced the older one and it does not get smoked it just keeps the fuel pump running.

I tried a bit of an experiment and placed a large fan on top of my motor ( same vehicle and amenities as you) aiming at my TFI (relocated to the fender) and after about 15-20 minutes of running she sputters and dies out. So moving it further forward near the radiator fan is pointless. I did some digging on the wiring (while checking the coil- thinking perhaps the coils windings could be bad causing the TFI to overheat) I pitched this problem to my brother and he asked me if there was a resistor going to the wiring of the TFI. There is. I have not tested it yet because I’m still trying to figure out exactly how they got this electrical wiring set up on this vehicle I’m gonna include a picture of mine I wanted to see if yours is just like mine or if somebody has messed with it at some point because it seems a little odd. I have a green wire with yellow stripe coming off of the coil as well as I’m assuming it’s a plug from the ignition and that joins up with the green and yellow wire with the resistor coming from the ECU and they all seem to converge into the TFI although I cannot find the green and yellow wire coming from the plug in the schematic in the manual. When you get the time or if you can actually take a look and see if these green and yellow striped wires come together in yours like it does mine. In the pic you can see The green wire with the yellow stripe and resistor joining the two coming up from the bottom right to the junction that I uncovered. it’s bare copper now as you can see and those three turn into one and that goes to the TFI.

 

[Bronco 2 man]

The two tan wires do they have a red stripe?

 

[Bronco 2 man]

I see they come together like the green one’s

 

[Mhollis1]

I see they come together like the green one’s

They appear to be tan with a black stripe but there is a tan w/ red that goes to a diode and comes out green w/white stripe on the other side