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86 2.9l Bronco II "bucking and jerking"/ Desperation!!

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86 2.9l Bronco II "bucking and jerking"/ Desperation!!

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Old 04-01-2012, 09:06 PM
chrislang
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86 2.9l Bronco II "bucking and jerking"/ Desperation!!

Newbe here with 86 2.9l 5 speed.

I know you guys must have had this discussion come up, but I searched and cannot seem to find an answer.
Issue: Starts up and idles fine. As soon as it warms up, it begins to miss a little. Try taking off, and as soon as it is under a load it will buck and jerk violently. I just bought this, because it is in such good shape. No rust, immaculate interior.
The guy I bought it off of has tested virtually ALL of the sensors, changed both fuel pumps, replaced the tank with a BRAND NEW one, new cap, plugs and wires.... NO CHANGE...

Could it be a vacuum issue,(can't find any) Timing? (set 10deg. BTDC)..Cold spark?

I know you guys must have discussed this ad nauseam in the past. If so, please point me to the link.

I really like the BII and am determined to find the issue. I hope you guys can help. Any and all comments will be appreciated!!

Thanks in advance!

Chris
 

Last edited by chrislang; 04-17-2012 at 08:49 PM. Reason: Added to title
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  #2  
Old 04-02-2012, 01:34 PM
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a few things i would check would be the egr valve. they are cheap and i would recommend just replacing it. along with the throttle posistioning sensor..i beleibe your bII should have one of those as well
 
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Old 04-04-2012, 07:23 PM
chrislang
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Well, I said it idles fine. But I have found that on a cold startup, it will idle fine AT FIRST. Then, as it warms up, it will start to surge a little, then sputter just a little bit. But, after it is warm it will not surge or sputter. After a while it may or may not go through this cycle. It still requires you to accelerate hard in between shifts to keep it from "bucking"

Anybody know what it is? I plan on checking for SOLID grounds, may replace the stupid O2 sensor, and maybe the TPS.

NEW fuel tank. Both fuel pumps are new and pushing plenty of pressure.

Timing at 10* BTDC

Proper plugs 42Cs

New cap and plug wires

New TFI

Please help if you can.

Thanks!
 
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Old 04-08-2012, 06:07 PM
Lead Head
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O2 Sensor is something to change. They are only reliable for around 60,000-100,000 miles. TPS possibly not but likely. I doubt he tested the MAP sensor though, as they output a variable frequency, rather than a voltage. They occasionally go bad.

Is the timing at 10*BTDC with the SPOUT connector removed?
 
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Old 04-08-2012, 10:20 PM
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O2 Sensor is something to change. They are only reliable for around 60,000-100,000 miles. TPS possibly not but likely. I doubt he tested the MAP sensor though, as they output a variable frequency, rather than a voltage. They occasionally go bad.

Is the timing at 10*BTDC with the SPOUT connector removed?
Thanks for the suggestion. I guess I could try that. I bought it from an individual who is an excellent mechanic,(he has checked everything with his meters) but as we all know, simple things often go overlooked.

I have the same scenario as this guy did, from another forum. I'll post it, as it may be helpful:

Posted <ABBR class=published title=2008-12-15T15:53:03+00:00>15 December 2008 - 07:53 AM</ABBR>
<!--cached-Mon, 02 Apr 2012 16:09:33 +0000-->BRONCO 2 CURSE!!!!!!!



Well if anyone ever comes up with a resolve for this problem, and it is a common problem as I have found through this and other forums, Please let me know. It appears that the 86 and 87 Bronco 2's with a 2.9 were plagued with this problem, and as I have found no-one has ever been able to resolved the problem once it starts. I've read numerious forums and they all say the same thing. Runs great when cold, reaches normal tempertature and it starts missing and bucking like a, well for lack of a better word "BRONCO". First start it up and it runs great till it reaches normal opperating temperature and then it all starts going down hill. Black smoke, missing shaking, no power. You can cut the switch off and right back on and it will run great for a few of miles and then it happens all over again.

I give up. I've now parked this 87 Bronco 2 parked right beside my other 87 Bronco 2, with the same problem. Yep they both have the exact same problem and they both have all new sensors, new ECM, new vacuum lines, lots of new wireing. One has a new distributer and the other one has a rebuilt distributer.

Heck now this one even has a brand new, complete distributer, and oxygen sensor. Everything that I can find that could be a possiblility, has been replaced. still no resolve. From what I hear this must be the Bronco 2.9 curse!! Oh yes I failed to mention I took the plentium off and cleaned it and the intake. re-installed it with new gaskets.

Last ditch effort! Took it to FORD and they couldn't find the problem either. They said it could be the ECM, but that was not a gurantee. Well i didn't got that route as the ECM had already been replaced.

Any body want a good deal on either of my Bronco 2's, both with lots of new parts? Can't say they run too well, except when cold they nrun great, but the both look good, just setting there! I've resolved now that it is an uncureable curse!

WARNING!!!! Beware of the Bronco 2 curse!!




0 <HR><!--Begin Msg Number 89254-->
#10 ronmar1
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Posted <ABBR class=published title=2009-02-08T17:41:18+00:00>08 February 2009 - 09:41 AM</ABBR>
<!--cached-Mon, 02 Apr 2012 16:09:33 +0000-->THERE IS A GOD!!!!

In a last ditch, desperation attempt, I went out this week, and bought another ECM for my BII. I pulled the recently replaced ECM, and intalled the new one.

With a prayer and and being very carefull not to get my hopes up, too much, I got in and started the engine. Sounded fine, but it is only after warm-up that the usually missing and sputtering started. So with great antisipation I waited till the temp hand got up to normal. Hey, it still sounded good! Could it be possible? After sufficent time for warm-up had pasted, the engine was still purring. I pulled it into gear and left my drive way. 30 miles later the engine was smooth as silk, and not even a miss. A great big smile crept across my face! Could I be mistaken? Could it be true? Not wanting to be too eager to proclaim victory over the curse, I took the BII home and let her set over night. This morning I went out and cranked her up. Guess what! Smooth as silk!!!!! I drove her around for a while and not even a hesitation!

Moral of the story? I don't know one, but I do know that, I will not ever again feel that replacement parts should be considered to be always good. Strange that the first replacement ECM would create the same problem code and symptoms as the original one, but it did.

Now if my neighbors will just forgive me for creating such a disturbance, with all my joyful bliss!!!!

Hope this helps someone else along the way. Just glad I didn't give up and call the crusher, although I did give it some serious consideration!!!

Thanks for everyone's input and attemts to help on this one!

Ron



Bold and underlines were added by me.

Now. I'm starting to think I may need to swap my ECU!
Question is: What is the part number needed for my 1986 BII 5 speed with only the Fed. emissions?

I have found the A1cardone ECU # 78 4393. Is there a better one? Would my VIN indicate the exact one needed?

Please help if you can. This forum is a great resource and much appreciated!!
 
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Old 04-08-2012, 10:33 PM
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Any 5spd bronco 2.9 86-87 ECU should work (88+ dropped EGR)

I suspect an 86-87 Ranger 2.9 5spd ECU should work as well.
 
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Old 04-09-2012, 06:20 PM
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Any 5spd bronco 2.9 86-87 ECU should work (88+ dropped EGR)

I suspect an 86-87 Ranger 2.9 5spd ECU should work as well.
Thanks for the info. Lead Head!

I would assume the the major differences would be whether or not it has Cal emissions or federal, standard or auto. Would the A/C option matter?
A1Cardone seems to be highly thought of. But, they list about 6 different ones. From what I gather, I need the one associated with Ford # E6TF-LA, or LB or LC. The guys at A1Cardone have their corresponding part number as: A1 78 4393 I am tempted to go ahead and get it, but want to check with you guys first. I'd like the input of anyone who has a clue. I am really starting to think it may be the ECU......... Could I be so lucky as well?

I think I will do these things first in this order:

1. Recheck all grounds.
2. New 02 sensor.
3. Remanufactored ECU, specifically for this 86 BII.

What do you think?
Please continue with any input on this.
Thanks!
 
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Old 04-09-2012, 06:39 PM
Lead Head
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I can't help you with the ECU selection. If all else fails, you may as well go for it. Just make sure you can return it though if it is not your issue.
 
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Old 04-17-2012, 08:56 PM
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Well, I replaced the MAP sensor-no change. I have replaced the o2 sensor with a new Bosch-no change.

I have a NOS Motorcraft TPS coming in the mail from ebay.........

If this does not work, what else??

Should I try unhooking the O2 sensor at the harness, and try that? Someone here said it worked for them.

Please, if you have ANY suggestions, any at all, please post them.

I will go the route of a new cardone ECM if I have to.

Thanks to each of you for your time. I have no where else to turn.

Once again, -no codes given with the OBD1.........

 
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Old 04-17-2012, 09:56 PM
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Just tried unplugging the O2 sensor------NO CHANGE..

What is going on??
 
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Old 04-17-2012, 10:17 PM
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Don't know what to tell you
 
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Old 04-18-2012, 01:10 PM
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With it running, use a screwdriver handle and "tap" on the ECM. Is there a noticeable change? Remove ECM and inspect for water damage.
 
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Old 04-19-2012, 10:42 AM
chrislang
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IT WAS THE ECM!!! A NEW ONE INSTALLED, NOW IT RUNS LIKE A NEW ONE!!!


 
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Old 02-13-2018, 07:42 PM
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QUOTE=chrislang;11729694]IT WAS THE ECM!!! A NEW ONE INSTALLED, NOW IT RUNS LIKE A NEW ONE!!!


[/QUOTE]

Originally Posted by chrislang View Post
Newbe here with 86 2.9l 5 speed.

I know you guys must have had this discussion come up, but I searched and cannot seem to find an answer.
Issue: Starts up and idles fine. As soon as it warms up, it begins to miss a little. Try taking off, and as soon as it is under a load it will buck and jerk violently. I just bought this, because it is in such good shape. No rust, immaculate interior.
The guy I bought it off of has tested virtually ALL of the sensors, changed both fuel pumps, replaced the tank with a BRAND NEW one, new cap, plugs and wires.... NO CHANGE...

Could it be a vacuum issue,(can't find any) Timing? (set 10deg. BTDC)..Cold spark?

I know you guys must have discussed this ad nauseam in the past. If so, please point me to the link.

I really like the BII and am determined to find the issue. I hope you guys can help. Any and all comments will be appreciated!!

Thanks in advance!

Chris
 
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Old 02-13-2018, 07:44 PM
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Hi Chris, this thread was awhile ago. If you recall what was the part number of the ecm you used and where did you purchase it ? Thanks Kenrick
 
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