Restore of my 1986 Bronco XLT

[Gary Lewis]

Yes, I've only disconnected it for testing.

But if this line is closed with open brakes, how could it have a leak?

The problem only occurs when the car is standing still and mostly when set in parking...

Is my idle not too low when cold? I've read the 347 stroker should have about 800 to 900 idle speed...

And about the vacuum value. Is it OK?

What could be the reason for the steadiness?

I don't see why the idle needs to be higher than ~650 RPM. And the vacuum looks good.

But I'm not sure that we are saying the same thing regarding the brakes and vacuum. The vacuum valve connected to the brake pedal should be closed when the brake pedal is up and the brakes aren't applied. If it was me I'd try to pull a vacuum on the line going to that valve. If it is leaking it could cause problems with the idle.

You can cap that line and test drive the truck. I wouldn't use the speed control, although it would probably be fine. It is just that the vacuum dump is a safety in case the system doesn't kick off when the brake lights come on.

[ReneH]

I don't see why the idle needs to be higher than ~650 RPM. And the vacuum looks good.

But I'm not sure that we are saying the same thing regarding the brakes and vacuum. The vacuum valve connected to the brake pedal should be closed when the brake pedal is up and the brakes aren't applied. If it was me I'd try to pull a vacuum on the line going to that valve. If it is leaking it could cause problems with the idle.

You can cap that line and test drive the truck. I wouldn't use the speed control, although it would probably be fine. It is just that the vacuum dump is a safety in case the system doesn't kick off when the brake lights come on.

So, I've found the problem. Actually it were two...

1st: the rpm, when warm was about 860 to 950...this seems to high. If I reduce it to about 720 to 750 with IAC disconnected, it runs very smooth without shaking.

2nd: the cable of the cruise control wasn't set correctly. It stops the throttles to reach the idle screw and holds the idle rpm high.

[ReneH]

So, I've found the problem. Actually it were two...

1st: the rpm, when warm was about 860 to 950...this seems to high. If I reduce it to about 720 to 750 with IAC disconnected, it runs very smooth without shaking.

2nd: the cable of the cruise control wasn't set correctly. It stops the throttles to reach the idle screw and holds the idle rpm high.

I have tested the 4WD today. It works so far.

But if I lock the hubs and let the car roll without giving gas, it makes not a good sound in my opinion:

What could cause this sound? As I don't need the 4WD in the upcoming holidays it's not very important...but good to know as I want to order new rotors, I can add the part that causes this noise...front axle bearings or propeller shaft? Differential?

[Gary Lewis]

I have tested the 4WD today. It works so far.

But if I lock the hubs and let the car roll without giving gas, it makes not a good sound in my opinion:

What could cause this sound? As I don't need the 4WD in the upcoming holidays it's not very important...but good to know as I want to order new rotors, I can add the part that causes this noise...front axle bearings or propeller shaft? Differential?

Rene - Several things.

On the RPM, if you have to unhook the IAC to get the RPM down then the computer is trying to keep the RPM too high. Or maybe it is the speed control cable? I'm not sure I understood that bit.

As for the noise, that is the sound of the transfer case in 4LOW. I'll bet it doesn't sound like that in 4High. That sound is normal given the straight-cut gears in 4LOW, and it is especially loud through the opening in the floor.

You do know that you aren't supposed to be turning corners on pavement with the hubs locked and the transfer case in 4WD - right?

[ReneH]

Rene - Several things.

On the RPM, if you have to unhook the IAC to get the RPM down then the computer is trying to keep the RPM too high. Or maybe it is the speed control cable? I'm not sure I understood that bit.

As for the noise, that is the sound of the transfer case in 4LOW. I'll bet it doesn't sound like that in 4High. That sound is normal given the straight-cut gears in 4LOW, and it is especially loud through the opening in the floor.

You do know that you aren't supposed to be turning corners on pavement with the hubs locked and the transfer case in 4WD - right?

OK, so maybe I've not exactly described what I've done. I've found a procedure to set/change the idle speed for the 302 EFI end of last year as I have had this big problems. That's the procedure:

Link to ford-trucks.com

So as having a 302 not anymore, I've read that the idle should be a bit higher.

Disconnecting the IAC is only while setting the new idle rpm.

My speed control cable wasn't set correcly, so it stops the throttle-plates to reach the idle-stop screw. That fact has nothing to do with the procedure itself. It's another issue.

About the 4WD: I know that not to turn corners on pavement as having no central differential.

But the noise occurs in 4High and also 2WD, haven't tested 4LOW. As hearing the noise first time with hubs locked and 4High set driving on a wet meadow, letting the car roll, I've set back to 2WD and do the samt test.

That's on the video:

Accelerating straigt on pavement with hubs locked in 2WD mode. Letting the car roll out. While rolling, you hear this noise. It seems to com from the front axle or propeller shaft...not easy to locate...but sure, sounds like straight-cut gears. Similar noise as driving in rear-gear with my CJ7 and let the car roll with pressed clutch pedal.

When unlocking the hubs, the noise isn't there anymore.

[Gary Lewis]

OK, so maybe I've not exactly described what I've done. I've found a procedure to set/change the idle speed for the 302 EFI end of last year as I have had this big problems. That's the procedure:

Link to ford-trucks.com

So as having a 302 not anymore, I've read that the idle should be a bit higher.

Disconnecting the IAC is only while setting the new idle rpm.

My speed control cable wasn't set correcly, so it stops the throttle-plates to reach the idle-stop screw. That fact has nothing to do with the procedure itself. It's another issue.

About the 4WD: I know that not to turn corners on pavement as having no central differential.

But the noise occurs in 4High and also 2WD, haven't tested 4LOW. As hearing the noise first time with hubs locked and 4High set driving on a wet meadow, letting the car roll, I've set back to 2WD and do the samt test.

That's on the video:

Accelerating straigt on pavement with hubs locked in 2WD mode. Letting the car roll out. While rolling, you hear this noise. It seems to com from the front axle or propeller shaft...not easy to locate...but sure, sounds like straight-cut gears. Similar noise as driving in rear-gear with my CJ7 and let the car roll with pressed clutch pedal.

When unlocking the hubs, the noise isn't there anymore.

I think Gacknar's procedure should work well.

But I disagree about the idle speed for a non-302 being higher. I don't see any need for the idle speed on your engine to be above 650ish once the engine is warmed up since you have a fairly stock cam. I would set the RPM where the engine idles well and smoothly, with the IAC just picking the speed up a bit, like the 40 RPM suggested.

As for the sound, I don't hear anything that sounds like bearings or u-joints. It all sounds like gears. I don't think I've listened to the noises Big Blue makes in 4Hi as I rarely use it in that mode. If I'm going into 4wd I usually go into 4Lo. So it is possible it makes that noise in 4Hi as well. But it doesn't make that noise in 2wd, even with the hubs locked.

So I'm confused. Have you checked that your front differential has lube? Have you lubed the u-joints on the front driveshaft?

[ReneH]

I think Gacknar's procedure should work well.

But I disagree about the idle speed for a non-302 being higher. I don't see any need for the idle speed on your engine to be above 650ish once the engine is warmed up since you have a fairly stock cam. I would set the RPM where the engine idles well and smoothly, with the IAC just picking the speed up a bit, like the 40 RPM suggested.

As for the sound, I don't hear anything that sounds like bearings or u-joints. It all sounds like gears. I don't think I've listened to the noises Big Blue makes in 4Hi as I rarely use it in that mode. If I'm going into 4wd I usually go into 4Lo. So it is possible it makes that noise in 4Hi as well. But it doesn't make that noise in 2wd, even with the hubs locked.

So I'm confused. Have you checked that your front differential has lube? Have you lubed the u-joints on the front driveshaft?

Ok, I've checked the idle rpm. As first written, 700-720 ist best without IAC connected. If I go too low about 600 and change from parking to drive, the engine is starving... so I've set it as written upon.

I've also adjusted my TPS sensor from .85 to 0.889. Can't get more without working on the screw holes...maximum is now 4.445 volts.

About the differential: I haven't checked...in my opinion this is a relative plausible cause...maybe the former owner never used the 4WD and hasn't serviced the differential and the u-joints.

[Gary Lewis]

Ok, I've checked the idle rpm. As first written, 700-720 ist best without IAC connected. If I go too low about 600 and change from parking to drive, the engine is starving... so I've set it as written upon.

I've also adjusted my TPS sensor from .85 to 0.889. Can't get more without working on the screw holes...maximum is now 4.445 volts.

About the differential: I haven't checked...in my opinion this is a relative plausible cause...maybe the former owner never used the 4WD and hasn't serviced the differential and the u-joints.

I'm confused. You should set the idle to something like 600 with the IAC disconnected and the transmission in Park or Neutral. Then when the IAC is connected it should bring it up to about 650. And then when the transmission goes in gear the EEC will bring the idle back to 650 via the IAC.

Is that not working?

[ReneH]

I'm confused. You should set the idle to something like 600 with the IAC disconnected and the transmission in Park or Neutral. Then when the IAC is connected it should bring it up to about 650. And then when the transmission goes in gear the EEC will bring the idle back to 650 via the IAC.

Is that not working?

No, when changing from parking to reverse or drive the rpm gets lower. Cause of the torque converter? It's normal, as far as I know...

Before lowering the idle, it was ok when the transmission goes into gear, but too high when in parking. Now both transmission positions are ok and the car isn't shaking anymore.

[Gary Lewis]

No, when changing from parking to reverse or drive the rpm gets lower. Cause of the torque converter? It's normal, as far as I know...

Before lowering the idle, it was ok when the transmission goes into gear, but too high when in parking. Now both transmission positions are ok and the car isn't shaking anymore.

The EEC should bring the idle back up to the set point when you put the vehicle in gear. And yes, the torque converter is loading the engine then. But the computer should compensate.

So, you are ok with what you have? It isn't shaking and you like the idle RPM? If so then I'd say that is success.