Suggestions Requested

[Afishhunter]

1986 Bronco II Eddie Bauer.
2.9 liter V6
Automatic Transmission
4 wheel drive
4.10 axle ratio, according to Ford.

NEW: (not used/rebuilt)
Distributor
TFI Module
Heads (Improved version)
In tank fuel pump, strainer, and fuel lines
Frame mounted fuel pump
All fuel filters
Spark Plugs and wires
Front transmission seal and bushing
Vacuume Modulator (Transmission)
Heater core

The fuel tank was removed, and cleaned with muratic acid prior to reassembly.

Tested at various shops:

Timing. The shop suspected the shop that replaced the heads and distributor did not disconnect the SPOUT connector, when they set the initial timing.
Result: "The timing is dead on the money at 10° BTDC with the SPOUT disconnected."

Vacuume
Results: 17 inches at idle. Increased RPM to 3,000 and held there.
Vacuume dropped to zero (normal) but did not build up vacuume after the engine stabilizedcat 3,000 RPM.
DIAGNOSIS: "Restricted Catalytic Converers" (This shop does not do exhaust, suggested a shop that does.)

Exhaust Backpressure at an exhaust shop.
They drilled two holes, tested the back pressure, and welded the holes closed.
Results: "No backpressure at the cats or muffer; you're waisting your time and money if you replace the cats."

Needless to say, these two shops consider the other to be owned and staffed by morons that do not know what they are doing. Both swear by their own analysist.

The problem:
No power under load and horrendous fuel mileage with or without a load.

The mileage varies between 5.5 in town to 10 on the highway, with no load. Obviously, the mileage should be at least double or triple this. My racing days have been over for no less thsn 40 years. I don't try to spin the wheels, etc. and go the speed limit.

I have a trailer I need to pull with this Bronco II. The trailer scales at 2,100 pounds.
The brakes were removed from the trailer, the wheel bearings repacke, and the grease seal was replaced.
The bearings are properly adjusted. (Wheels turn on their own when jacked up)

With the trailer attached, I can ALMOST hit 50 mph on level ground.
With the trailer left at storage, I can hit 65 mph with no problem.

I have a new O2 sensor, which will be installed Monday.

Any ideas as to what is wrong?

I KNOW this thing can pull this trailer. With the 4.1 axles and auto trans, the owners manual says a max combined weight of 8,500 pounds. I scale at a little over 6,000 pounds. Also, this Bronco II has pulled the trailer in the past, with no problems, at 55 to 60 mph, on level ground.

This thing has also gotten near 20 mpg in town and right at 30 mpg on the highway, without the trailer.

Thank you in advance, for your help.

 

[wildbill23c]

Brakes dragging? The brakes on my 88 B2 I think drag a bit...something I need to take a look at as they must be dragging a lot more seems it takes more go pedal to get it moving. Normally an automatic transmission vehicle will kind of start rolling on its own as soon as you let off the brakes but mine does not so I think the rear brakes are sticking...pretty easy fix and I just keep forgetting about it, but at the same time if I'm going to tear into them I may as well just get the stuff and replace the brakes while I'm at it LOL.

Possibly a transmission issue. I had the transmission rebuilt in my Bronco 2 earlier this year, on the drive home from the shop it seemed extremely sluggish, and the engine was really heating up...funny it never did that before, I started thinking ok now what's going on. I got home called the shop and told them what was going on and they said it may be the valve body in the transmission. Took it back the next day and sure enough the valve body was bad, it wouldn't shift into 1st gear on its own so I was taking off from 2nd gear, plus it wasn't going into overdrive either. They replaced the valve body and its been doing a bit better, but like I previously mentioned I think I have some brakes dragging now causing the power loss issue.

Another thing would cause a bit of power loss would be the fan clutch being stuck in the engaged position. This pulls a lot of power spinning that fan at full speed all the time. Shut the vehicle off and try to spin the fan, it should spin somewhat free, if not the fan clutch is shot and needs replaced.

 

[JerryC]

What size tires?
How long have you had this problem?
Long enough to get a new tank of gas?

 

[wildbill23c]

20mpg city and 30mpg highway with 4.10 gears, how do you manage that? Downhill all the time?

I forgot to ask earlier is your parking brake sticking or the linkage sticking? This will surely cause some definite power and fuel economy loss.

 

[buck119fa]

Torque converter, they can cause this symptom as well. How does the trans shift? soft or hard, what color is the fluid, smell burnt?

 

[Afishhunter]

What size tires?
How long have you had this problem?
Long enough to get a new tank of gas?

The tires are standard 215/75/R 15 "all terrain".

I've had problems with it for years; acting like it is out of fuel when the tank is full, won't run when warmed up, etc. (several fuel pumps, fuel filters, and ignition modules later, I find out that problem was caused by a bad TFI sensor)
The truck sat for 9 or 10 years. Would not start, so took it to a shop. They replaced tge distributor. It started "and runs great". Go to pick up the thing, won't start. No compression on two cylinders, low compression on the rest. After some research, I determine it has the old head design. The heads need rebuilt, sucking at least one valve, so I order a set of new, improved heads, and have those installed.
After the heads and everything else overvthe ladt 3 weeks, I've filled the tank several times. Mileage ranged from 10 to 13, then dropped to 5 something.

Just filled up again today, after the O2 sensor was replaced.

 

[Afishhunter]

Torque converter, they can cause this symptom as well. How does the trans shift? soft or hard, what color is the fluid, smell burnt?

Shifts fine. Had to replace the front seal and bushing. Also had the tranny serviced, new filter and fluid, and a new vacuume modulator. That was 3 days ago.
The old fluid was pink, no burnt smell, and the pan was clean on the inside when it was taken off.

 

[Afishhunter]

20mpg city and 30mpg highway with 4.10 gears, how do you manage that? Downhill all the time?

I forgot to ask earlier is your parking brake sticking or the linkage sticking? This will surely cause some definite power and fuel economy loss.

2200 rpm at 55 in overdrive. 2800 rpm at 55 in 3rd, roughly 3100 rpm at 60 in 3rd.
I don't expect 30 plus mpg on the hiway like my XLT got (Bronco II, same engine, but a 5 speed manual instaed of tge automatic) but the 4.1 gearing should not cause a mileage penalty in the top gears, since Ford appears to have put taller ratios (lower numerically) in to compensate. Kind of like a semi with 5.3 or so in the rear(s) even at 60 mph your engine is only turning 1700 give or take rpm.

Brakes are not dragging or sticking.

 

[Afishhunter]

I've done all the obvious, including taking roughly 1500 pounds out of the trailer, removing the ancient trailer brakes (were not even connected during the 20 odd years I've had the trailer. They DID start dragging, found a broken spring in them. Also repacked the wheel bearings.)
In over 40 years of wrenching, I've never run across a situation like this. I'm stumped.

In "perfect 20/20 hind sight" I should have scrapped or sold this thing and used the 5 grand spent on repairs to buy something else. I KNOW I'll never get my investment back.

 

[JerryC]

Ok, so I'd start looking for a vacuum leak and checking the sensors.
ACT and ECT. Those three things will send your air/fuel ratios out of whack and send your mpg down the drain. If you're lucky it was the O2 sensor that you just replaced.

Oh, you might try running some fuel injector cleaner through it for a couple of tank fulls. If the spray pattern is bad, that would do it too. Sitting for years may have killed them by gunking them up.

Does the 86 have an EGR system ?

 

[Afishhunter]

Not sure if it has EGR. I don't see any EGR tubes coming off the exhaust manifolds, but I suppose Ford could have internalized the EGR system.