BroncoII4x4.com

My 1986 Bronco II is getting poor fuel economy (around 12-13 MPG). What is causing this? Bad ignition timing?

Sorry for this simple problem and question, as I am not heavily skilled in automotive mechanics.

That's a pretty open ended question. Has there been a recent change in fuel economy? What engine, tranny and gears do you have? Tire size & and type?

Here are the things I think affect fuel economy the most.

1. Driver and type of driving.

2. Overall condition of the engine.

3. Choice of fuel. Depending on your location, you may be getting the "winter fuel" which takes a toll on mileage.

4. Tires and air pressure.

Nobody wrote:That's a pretty open ended question. Has there been a recent change in fuel economy? What engine, tranny and gears do you have? Tire size & and type?

I have a fuel-injected 2.9L V-6 with roughly 138,000 miles on it, automatic transmission (4-speed, I think), and I am not sure about the gears (they are probably stock).

Here are the things I think affect fuel economy the most.

1. Driver and type of driving.

I drive it. I don't have a "lead foot." I usually do combined driving (highway and city).

2. Overall condition of the engine.

It seems to be running fine at 138,000 miles. I am losing coolant, and there are no signs of external leaking or leaking into the oil (I am getting this checked soon. It can't be a bad readiator cap, as I just replaced it).

3. Choice of fuel. Depending on your location, you may be getting the "winter fuel" which takes a toll on mileage.

I am using "winter fuel" (this is Minnesota), but it has been getting bad economy ever since I purchased it (since October 2003). I thought "Oh, it's an SUV. It is going to get bad mileage. After I did some looking up of info, I realized that my mileage is very bad). If anything, it has been getting a little worse.

4. Tires and air pressure.

I believe that the width is 205, and that the pressure is 35 psi. I keep an eye on the pressure.

Maybe I will get this checked tomorrow as well, if the mechanic has time (I know him personally, so I just go to his house for such things if possible).

Well, the loosing coolant throws a red flag. Definately sounds like a head gasket issue, which certainly can affect mileage. Pull the plugs and see what they look like. They are the best indicator of how your engine is running.

Automatics generally get worse milage than a manual tranny.

I'm not sure what the BII was rated at from the factory, but I'd guess 18.

Nobody wrote:Well, the loosing coolant throws a red flag. Definately sounds like a head gasket issue, which certainly can affect mileage. Pull the plugs and see what they look like. They are the best indicator of how your engine is running.

Automatics generally get worse milage than a manual tranny.

I'm not sure what the BII was rated at from the factory, but I'd guess 18.

The old plugs were in bad shape, but then again, the mechanic, of whom I know, said that they were the wrong type of plug.

I am really worried about the coolant loss and such. I hope that it is not an issue with a cylinder head and such, given that one would pretty much have to overhaul parts of the engine and such to solve that problem, I think. That would take a long time and cost a lot of money. Maybe I would almost be better (if this is the case) off trying to get a .302 V-8 in the truck instead, for those engines are rather cheap, given the mass quantities of them produced. Wait...ach, crap! I would need a new tranny and all sorts of stuff if I dropped a .302 in, wouldn't I?

I'd do a 302 swap again in a heart beat. Heck I get 13-14 with No overdrive and 36's. But yes the 302 can be a can of worms, where you'll end up needing better tranny, and axles.

The 4.0L on the other hand is a good alternative. It will drop right in, and should improve milage.

Nobody wrote:I'd do a 302 swap again in a heart beat. Heck I get 13-14 with No overdrive and 36's. But yes the 302 can be a can of worms, where you'll end up needing better tranny, and axles.

The 4.0L on the other hand is a good alternative. It will drop right in, and should improve milage.

The 4.0L must be the engine of the Ford Explorer Sport (which basically looks like a Bronco II with a new look), I take it. How much would a 4.0L Ford V-6 cost, as well as the labour to remove the 2.9L and replace it with the 4.0L?

Check out DBrown's 4.0L Swap

iv had 3 BII's and all of the just suddenly for no reason at all started getting bad milage the last one I had I tried to fix and just finnally said screw it and put a 5.0L in now I get better milage than it ever got :)

if you have to pay for someone to swap in a 4.0L they are going to rape you on labor. you better find someone that can wire EFI also because that is the hardest part of the swap. if you have a friend that can help you that will cut the cost quite a bit.

personaly I would run codes and see if anything comes up could be a $40 fix to get better milage.

Nobody wrote:Check out DBrown's 4.0L Swap

Ach! I don't know if I know how to do that, as I lack mechanical experience.

From DBrown:

if you have to pay for someone to swap in a 4.0L they are going to rape you on labor. you better find someone that can wire EFI also because that is the hardest part of the swap. if you have a friend that can help you that will cut the cost quite a bit.

personaly I would run codes and see if anything comes up could be a $40 fix to get better milage.

That is what I was afraid of. Whenever someone else does it for you, labor tends to cost the most.

I am going to get this checked, hopefully sometime soon. I will tell you what the mechanic says.

Well, the timing is dead on, so that was not the problem. The mechanic (he knows me, and I was not in a shop) stated that it could be a number of things, and it would probably be pretty expensive to take care of things. He said that I might as well drive it until it pretty much quits, then decide on if I want to put money into restoring the vehicle or getting something else.

autozone will pull the codes for free and they will tell you exactly what is wrong with your truck. that is why I suggested it. they can even price you the part right on the spot. it's at least worth looking into.