Did a few searches and havent found much so I will ask. I have a 89 full size bronco with a 5.0 and an AOD tranny. Aftermarket mods include Eldebock performer heads (broken in). MSD distributor, MSD coil, MSD plug wires, BBK throttle body, and K%N filtercharger. I plan to install my Hooker super comp headers once i can get the exhaust biult for me. Possibly as well a mass air flow mod.

When I pulled my old heads off a friend of mine who is certified looked at the piston shafts and said they were great very smooth with no scratches. The rings looked good as well. I have changed the oil twice since then driven right at 6000 miles.
All problems with the truck seem to be very small while cold, ( first thing in the morning driving 0-5 miles). After that anytime during the day problems are there. Engine temp rarely gets to "N". Engine leaks about a quart of oil every month. I add as needed.

1. A hard shift. Had U joints replaced 3 months ago, they had gone bad(sloppy play), afterwards problem was same as before. I have tried to twist the drive shaft with the truck in park, it won't budge at all.

2. At 35 and at 45 mph when letting of the gas, truck will downshift. Then literally a second later upshift. Some people had suggetsed tighting the Pinion nut for this. Tranny fluid looks good been replaced 11 months ago. There is a very very small leak out of the linkage though.

3. Oil pressure fluctuates from (using normal) "R" to "N" while driving. Basically it dows what it wants when it wants.

4. While slowing down to a light. Right before I stop (maybe 2 inches at most). There is a clunk. Almost like the driveshaft is still sloppy and the tranny is slamming it into the rear diff. The clunk also happens when I pull off from the light, a foot or so after starting to roll. I believe this is also related to the hard shift.

5. While slowing down to a light my idle die's to about 500 rpm. then jump back up to a grand while at the same time slamming the tranny shaking the whole truck. If I aproach slowing down well slowly, and not slamming the brake, I can control the idle dieing better and the tranny doesn't jump, but the idle will jump back to a grand.

6. While sitting still, I can press the brake and the idle will noticably drop about 50 RPM or so. I let off the brake and it goes back up. I know that my vacuum line off of the smog can will not stay on no matter what I do, but could this cause such a large problem? I figure I have more of a leak somewhere. Possibly from changing the heads.

7. There is a constant roar from the rear diff. Sounds like a cross between going really fast in reverse and driving on the interstate with superswampers at 70. Back in january i had the bearing changed in it. the mech said the ring and pinion where fine afterwards all good no noise whatsoever. It came back 4 months ago as a light sound, while driving at 45 mph, only to steadily increase over time. Now instead of doing it only at 45 mph, it does it from 25 to 55 mph.. Going back to him is impossible.

8. Did a diognostic, KOEO and KOER tests several months ago. All I remember from both showing the throttle position sensor was out of range or something to that nature and the egr valve opening not detected (33). Changed out the TPS, the egr sensor, and the egr valve but no luck. I will do another diagnostic soon to get the codes again.

9. My back window will only go up if I use the door switch. Door switch works fine but the console switch only works in down. Plus to make matters worse the tailgate will not let down for any reason. Seems the right latch is faulty and won't unlock.

10. It takes a good 10 tries of priming the fuel pumps (key on hold key off, rinse, repeat) to get the truck to start after it has sat overnight or for a day or so. After that it starts fine.

11. Also now there is a rough idle. And at times the truck will die for no reason, just for half a second then go back up to idle. Other times it dies compleatly. It only hapens at idle.

Any help will be apprieciated. Oh and This has been making me mad for a while.

 

Phew....that's a mouthfull......Let's see......for the first 2,I believe the AOD uses a TV Cable to tell throttle position instead of a vacumn diaphram.Proper adjustment of the cable is critical to proper shifting.It controls pressure to parts of the valve body and circuits in the tranny.It might fit in to a plastic grommet that may be broken,It could cause strange shifting and downshifting too.....

Oil pressure could just be the sending unit taking a dump or the gauge itself..The only real way to tell is to put a real gauge on it and see what the pressure actually is.

You say you had a bearing replaced in the rear diff?The noise was gone then came back.What bearing did he replace?If he replaced the inner or outer pinion bearing and didn't set the preload correct it could cause the bearing to fail.That's what it sounds like.One of the bearings in the diff is howling.Hope I'm wrong on that one.

As for the mutiple tries to get the truck to start,Could be the pump in the tank going out.Can you hear it running when the truck is?Usually if you can hear it,it's getting on in age.Could be the regulator on the fuel rail also.Maybe the fuel filter?

The brake/idle issue.....Could be the brake booster has a leak internally that only opens when the diaphram is moved due to the pedal being pushed.That ones unusual but possible.

Not sure about the oter's.They could be related to each other.Best of luck to you.

Chris.

 

Well first of I am an electrician on F-15's for the Air Force so my mechanical skill and trouble shooting are at least at a descent level.

The oil pressure gauge and sensor are working fine because as I gun the engine the oil pressure increases. As the idle dies when I approach a light, the pressure dies as well.

The mech said he changed out all the bearings and that the ring and pinion were fine. No visible damage or undue wear on them.

Yes the pumps are audible at all times. Sometimes the engine will die for a split second and come back leading me to believe the pumps are dieing. Filter has been changed twice for good measure in the last year. I only go with Fram.

Could my TV cable going to my tranny have been torqued when I changed out my heads? Would this cause the shifting problem? I did have them sitting off to the side with the trottle cable.

OK you have to tell me exactly how the brake booster works. I know it operates off of vacuum pressure ( or at least that is what I have been told) so since I know that I have a vacuum leak somewhere, could this added loss of vacuum due to the brake being pushed cause my idle to drop further?

 

not sure which year they switched to fake oil pressure gauges but im almost sure it was prior to 89. the fake gauge acts as a light at something like 3.5 pounds it reads normal and below it reads none (unless of course its been changed out with a real one) so it could be a ground problem with the sender.

 

I was having similiar problems as far as the shifting and down shifting goes and it was my vehicle speed sensor in the transfer case. Cost less than $25. from Ford. Try cleaning your throttle body with TB cleaner only, not carb cleaner. While you have it off, replace gaskets and clean / replace the air bypass valve. Also, replace the throttle position sensor since it is cheap and easily done while the TB is off. My 89 is the type that does not need adjustment, some need it though. My oil pressure has fluctuated for the past 12 years but has been more steady the past year since I started ading a qt of Lucas Oil Stabilizer to each oil change. I also added a couple of qts of Lucas Transmission additive to the tranny and made a noticable difference in the smoothness of the shifts as well. I would drain the rear diff and refill with the proper fluid and additive since this never hurts. The rough idle and stalling could be resolved maybe by the above cleaning. When you start your Bronco, do you just get in and turn the key ? If so, turn the key to on until the pumps cycle for 2 seconds and try it that way and see if it makes a diference.

Long winded huh ? Sorry.

Good luck.

 

Nah I was long winded.

It has a regular oill pressure guage.

Haven't thought of the speed sensor yet. It could have been damaged when the mech replaced everything in the diff.

It has a new BBK thottle body on it. So it is clean. I have installed a new TP sensor on it and it has new gaskets. However the Idle air bypass valve I believe is working correctly because at startup the engine has the high idle untill I hit the gas or untill it warms up ( working as advertised I beleive).

Put lucas in mine when I could find it and yes it works better than anything I have ever seen. I also have just purchased a bottl of lucas tranny fluid so we will see what happens with that.

When I start the truck in the morning yes I must turn the key to run wait a few seconds turn it off and repeat this process a few times to get it to start. When it does this it starts perfectly. In the afternoons usually no problem whatso ever.

Anyone knowledgeable in the point of fuels pumps please tell me if this could be the high or low pressure pump.

Thanks

 

Hard shift? Clunking? Roaring noise? I had all similar issues until I dropped the rear shaft, lubed the slip joint and most of all tightened the pinion nut where the rear diff attaches to the shaft. Fixed 100%

 

"9. My back window will only go up if I use the door switch. Door switch works fine but the console switch only works in down. "

I think I might be able to help you with this one. If you take your dash switch apart, and look at how it works, you will see four sets of "points." They are brass or copper and get bent over time in one direction. This can cause the window to only go in one direction, or cause one switch to work and no the other.

It's easier for you to take it apart and look at it then for me to try and explain it, it only took me a few minutes to figure it out after I took it apart. It's hard to explain, just push them with your fingers (not something metal) with the key on and you will see how it works. Remember that they have to be bent just right, if you bend it back too far it can cause the opposite problem. It's pretty nuch trial and error for a few minutes, but it's free (cheaper than a new switch!)

One hint: if you have someone at the back with the door key, operating the back window when you tell them to, it makes this easier. I have had to do this twice to my switch in two years, and it involved bending the tabs so the front worked, then takking out the key and going to the back, and testing that; I had to do that several times before it was adjusted perfectly and it gets annoying.

 

Anybody else have some idea's???

 

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Looking through a few other threads and some one else said it better than I did.

By Wolfman2405

88 Bronco 302, AOD tranny.
I have had this problem over the last few months but thought nothing of it. I changed my tranny fluid and filter(along with torque converter fluid). Shifting is just fine no problems I even seem to have a little more power in OD than I did before the fuid change. But the problem I am having I had before the fuid change, when slowing down to stop the RPM's drop to 400 then SHOOT up to 1,100 with a hard downshift from 2nd to 1st. I think it is my ideling, my Bronco idles with a warmed engine at 800-1,000RPM's in park or in gear.
I think that idle is too high, my idle speed went up after I cleaned out my IAC valve, I removed the valve from the IAC motor so I did not get any cleaning fluid in the motor. What could the problem be?? the TPS?? if so can the TPS be cleaned in some way??
Also could resetting the computer fix this, does it need to relearn the IAC now that it's clean??
EDIT, I just thought of something, I really OPENED up my air intake, could that be the problem???? Too much air???
Thanks,


Same prob as mine, STarted to drive the vehicle in Drive instead of Overdrive and the problem compleatly disapeared, as well as the hard shifts. People in his post said it was possibly the Torque converter. My Tranny fluid was changed last november.

Any body else got an idea?????

 

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Ok now since I have been driving while the tranny is in 'drive' for a week now it is started to have the same hard shifts like it did while I had it in 'OD'. Any body with good tranny knowledge have any idea's?