Good morning, I hope someone can help me with this problem, it has been driving me crazy for a couple of months now and I just found your site on google.....I have a problem with the bronco II when I first begin to drive it sometimes it will begin to stumble and if I accelerate it will downshift and continue (automatic with overdrive) once it upshifts and goes back to cruising speed it will do it again I start all over, up and down as it stumbles and hesitates......other times it will start off ok and will run fine with no problems at all until I stop for coffee and turn it off. I get back in and start it up and take off it goes back to the stumble and downshift all over again......when it is going to run like this I can tell almost from the very start that it is of isn't going to do it......now for the best part of all, when it is acting up and I come to a stop sign or just pull over and come to a complete stop it will not run bad any more 95% of the time and all is well. If it starts out from the start running good and I do not turn it off and restart it the problem does not occur until the next time that I start it up.....maybe. Hope all this makes sense as this is driving me crazy.......like the damn thing.....and do not want to get rid of it as it is in great shape for its age and NO RUST.....Live in OHIO and everything rusts here. Any help would be greatly appreciated......Have a nice and thanx
1986 Bronco II problem
- Thread starter popeye46
- Start date
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andre
New member
check if down shift cable not stuck best bet is remove cable from tranny
not hard to do try it out to see
also check vacum hose to tranny modulator valve
not hard to do try it out to see
also check vacum hose to tranny modulator valve
popeye46
First, check each and every vacuum line, hose and connector. Chances are you have some sort of a vacuum leak, I think most of these older B2's do. There should be a sticker under the hood showing the routing of all these hoses. (What year is yours?) Also, replace the PCV valve (a few bucks) just to be sure.
And it wouldn't hurt in diagnosing the problem to get a code reader (if your vehicle has an engine codes computer) and see if you are getting engine error codes, and if so, which ones.
That said, your problem sounds very similar to the beginning of a problem I had for YEARS. Doesn't get better, gets worse with time. After changing out numerous parts and checking many things, (it eventually became almost undriveable, with terrible gas mileage) I pulled the connector off the O2 sensor located on the exhaust pipe just before the catalytic converter. Instant end to the problem. (Bad O2 sensor, with NO "check engine code" to indicate a bad sensor.)
Might be a solution for you, might not. But easy to check.
Good Luck.
CraigK
First, check each and every vacuum line, hose and connector. Chances are you have some sort of a vacuum leak, I think most of these older B2's do. There should be a sticker under the hood showing the routing of all these hoses. (What year is yours?) Also, replace the PCV valve (a few bucks) just to be sure.
And it wouldn't hurt in diagnosing the problem to get a code reader (if your vehicle has an engine codes computer) and see if you are getting engine error codes, and if so, which ones.
That said, your problem sounds very similar to the beginning of a problem I had for YEARS. Doesn't get better, gets worse with time. After changing out numerous parts and checking many things, (it eventually became almost undriveable, with terrible gas mileage) I pulled the connector off the O2 sensor located on the exhaust pipe just before the catalytic converter. Instant end to the problem. (Bad O2 sensor, with NO "check engine code" to indicate a bad sensor.)
Might be a solution for you, might not. But easy to check.
Good Luck.
CraigK
Thanx for the reply. I saw your reply to another individual about the 02 sensor and that was the first thing that I tried.....nothing......didn't run better or worse.....I will check all of the vacuum lines and connections to see if that is what is causing anything......it is funny that when I come to a full stop when it is acting up and then continue on it seems to cure the problem......could there be a link to the transmission that would cause this problem......such as the vacuum modulator located there......I appreciate your time about this as it is fslowly driving me crazy.......by the way it is a 1986 with the 2.9......would also like to put in a 4.0 from an explorer but that is a ways down the road......My grandson will get it after I do that......thanx again and I will try what you suggested and get back to you.......Mike
Try this, There are square relays on the passenger side over the front tire. Get the vehicle running when its not acting up and with your pointer finger just tap them, one at a time, and if it starts to stumble you found the problem. I had a similar problem years ago and it cost me $$ to find out this little ditty. You'll be surprized . If it works, good. Geo.
popeye46
If you look back at the first response to your initial question, "andre" suggested checking the vacuum line to the tranny modulator valve. On my '87, this vacuum line goes from a T connection at the back of the engine back down to the tranny (it also T's off to the brake assembly). Again, if you have a vacuum leak in this system anywhere, it will effect the vacuum going to this valve also. And remember to replace that PVC valve!
CraigK
If you look back at the first response to your initial question, "andre" suggested checking the vacuum line to the tranny modulator valve. On my '87, this vacuum line goes from a T connection at the back of the engine back down to the tranny (it also T's off to the brake assembly). Again, if you have a vacuum leak in this system anywhere, it will effect the vacuum going to this valve also. And remember to replace that PVC valve!
CraigK
