1990 bronco 351

ive got a 1990 bronco with a 351 and im getting less than 10 mpg, and i have no idea why, i dont drive it hard and its in fairly decent shape, can someone give me some help?

When was the last time it was tuned up?

i am not sure i just bought it but the oil looks fresh and the plugs arent burnt, it does smell a little rich while its running.

yo 90bronco86,

Also the Check Engine Light (CEL) comes on when the electronic engine control system is not working properly. The check engine warning indicator comes on briefly when the ignition switch lock cylinder is turned to ON, and should turn off when the engine starts. If the check engine warning indicator does not come on when the ignition switch lock cylinder is turned to ON or if it comes on while the vehicle is moving, the system is malfunctioning

If the CEL does not light up at all when starting it; then suspect that someone removed it.

So is CEL lit at any time?

Regardless, try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19

The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test.

Run it around to heat the engine up and shift thru all gears incl Reverse. Then turn off all accessories/lights, etc.

Make sure A/C is off and transmission is in Park (automatic) or in Neutral for a Manual & release clutch.

Do Key On Engine Off (KOEO) portion first.

Look Codes up in my broncolinks.com site using the new Search function.

And Post em here according to:

KOEO

&

KOER

===========

Pull and inspect a few spark plugs

Misfiring spark plugs may cause an unburned fuel air mixture to pass through the catalyst, which could cause higher than normal catalyst temperatures.

Firing End Analysis, General Source: by gnttype.org

The Cel light comes on when the key is in the on position but goes away when I start the truck. And I haven't noticed it coming on while driving. But when the key is in the on position the cel does not go off untill I start the truck.

And in an un related question why does my 90 have auto hubs but a manual floor shifter. All the broncos ive seen from 89 on have hadbpush button 4wd.

yo,

OK, do that Self Test for Codes anyway

You are lucky to have that BW1356 manual transfer case!

But, the auto locking hubs get iffy, mainly due to wear esp lack of maintenance (cleaning & lubrication) and over lubrication, grime, mis-use, etc., etc.

Take ttme to read this by Ford

Four Wheel Drive (4X4) General Information, Operation & Troubleshooting TSB 92-1-8 for Bronco, F Series & Ranger (COMPLETE); Includes Electric Shift On The Fly (ESOF) Troubleshooting & Hub Operation, etc.

miesk5 said:

yo,

OK, do that Self Test for Codes anyway

You are lucky to have that BW1356 manual transfer case!

But, the auto locking hubs get iffy, mainly due to wear esp lack of maintenance (cleaning & lubrication) and over lubrication, grime, mis-use, etc., etc.

Take ttme to read this by Ford

Four Wheel Drive (4X4) General Information, Operation & Troubleshooting TSB 92-1-8 for Bronco, F Series & Ranger (COMPLETE); Includes Electric Shift On The Fly (ESOF) Troubleshooting & Hub Operation, etc.

Click to expand...

M

Does me having the BW1356 t case give any clue to what transmission I have? I know there is a way to look it up on the door placard but mine was painted over.

my 90 with a 351 has an E4OD the pan has 20 bolts holding it on. thats how i figured out what mine is. There are other ways to identify transmissions like paticular pan shapes number of pan bolts the presence of or lack of a vacume modulator but when i went to but the filter and gasket for mine the guy asked me how many bolts are in the pan (20)= E4OD

yo,

as Elmo advised;

and some E4OD, AOD & C6 Pan Identification & Driver Side pics;

Source: by Kenneth at http://www.technicalvideos.com/identify_my_transmission.phtml

E4OD have 20 pan bolts

AOD have 14 pan bolts

C6 have 17 pan bolts

miesk5 said:

yo,

as Elmo advised;

and some E4OD, AOD & C6 Pan Identification & Driver Side pics;

Source: by Kenneth at http://www.technicalvideos.com/identify_my_transmission.phtml

E4OD have 20 pan bolts; P-R-N-D-2-1 shifter pattern - pic by Chris A

AOD have 14 pan bolts, see diagram & pic; P-R-N-(D)-D-1 shifter pattern, note, OD is actually a (D) - pic by trigger @ http://img.photobucket.com/albums/v663/RampageFSJ/a4-1.jpg

C6 have 17 pan bolts, see diagram & pic; P-R-N-D-2-1, shifter pattern - pic by miesk5

Click to expand...

Ok thanks, is there a transmission that better than the others? Because a few people have told me.to do a c6 swap on my truck.

Those adviseing you to do a C6 swap are baseing their advise on the old school experience that the C6 was one of the most dependable trannys of its day. I would not ever think of swapping my E4OD for a C6. While it is a good idea to strive for the best MPG possible keep in mind that we are talking about a vehicle with the aerodynamics of a brick on wheels. Now 10 is a bit low and considering that you just bought the truck i would say check out or have a reputable shop check out the truck for proper operation. Look for Diagnostic Trouble Codes(DTC) useing the manner described in earlier posts and address any that are found. Also check that the speedodometer is accurate and that the tranny is functioning properly and the converter is locking up like and when it is supposed to. Are we working on a stock truck factory engine suspension and factory reccomended tire size ? Help us help you by filling out your signature (on your profile page) with your trucks information and any mods that have been done.

Elmo said:

Those adviseing you to do a C6 swap are baseing their advise on the old school experience that the C6 was one of the most dependable trannys of its day. I would not ever think of swapping my E4OD for a C6. While it is a good idea to strive for the best MPG possible keep in mind that we are talking about a vehicle with the aerodynamics of a brick on wheels. Now 10 is a bit low and considering that you just bought the truck i would say check out or have a reputable shop check out the truck for proper operation. Look for Diagnostic Trouble Codes(DTC) useing the manner described in earlier posts and address any that are found. Also check that the speedodometer is accurate and that the tranny is functioning properly and the converter is locking up like and when it is supposed to. Are we working on a stock truck factory engine suspension and factory reccomended tire size ? Help us help you by filling out your signature (on your profile page) with your trucks information and any mods that have been done.

Click to expand...

As far as I know right now everything on the truck is stock accept the tires which are 33 12.50 15. And the tranny seems to be working fine, it doesn't slip or anything, the only thing ive noticed is it makes a small noise when going into reverse, but it wasn't anything I was concerned about, now it does smell like its running rich a little bit.

When i have the 33s on my truck with my gearing 355 i can see a difference in my milage i havent checked it but it is noticably lower than when i have 31s on it. At what rpm does the truck idle at ? A vacume leak could be causing the HEGO2 sensor to get a faulse reading therefore richening up the fuel/air mixture.

to get the best possible mileage without re gearing you would have to run 235/75R15 which is the stock tire size. I noticed a big change going from 235's to 31's but that's with my extremely low 3.08 gears. if there is nothing wrong with your trans I wouldn't even consider a c6 swap, with the right gearing overdrive can be a gas mileage savior, wrong gearing and it will just **** the gas right out of your tank. If I were you I would consider going to a 32 or 31" tire size when its time to replace those 33's if you don't want to re-gear.

Elmo said:

When i have the 33s on my truck with my gearing 355 i can see a difference in my milage i havent checked it but it is noticably lower than when i have 31s on it. At what rpm does the truck idle at ? A vacume leak could be causing the HEGO2 sensor to get a faulse reading therefore richening up the fuel/air mixture.

Click to expand...

In park it idles around 1200 hut when I put into drive it goes down to about 700. And I have an E40d transmission, I counted 20 bolts on the pan, I also noticed I have a leak from the pan, and I'm missing the plug for the bell housing, could that cause problems?

Krafty said:

to get the best possible mileage without re gearing you would have to run 235/75R15 which is the stock tire size. I noticed a big change going from 235's to 31's but that's with my extremely low 3.08 gears. if there is nothing wrong with your trans I wouldn't even consider a c6 swap, with the right gearing overdrive can be a gas mileage savior, wrong gearing and it will just **** the gas right out of your tank. If I were you I would consider going to a 32 or 31" tire size when its time to replace those 33's if you don't want to re-gear.

Click to expand...

I'm not sure if I should re gear, it's my daily driver and the hardest thing it will ever do is pull my mudtruck on a trailer.

the point i was trying to make was that your engine is working harder just to move the 33" tires over the stock sized tires. The re gearing would provide stock like mileage and performance and would cause less wear and tear on your drive train than in its current configuration. the next best solution to re-gearing is smaller tires.

Krafty said:

the point i was trying to make was that your engine is working harder just to move the 33" tires over the stock sized tires. The re gearing would provide stock like mileage and performance and would cause less wear and tear on your drive train than in its current configuration. the next best solution to re-gearing is smaller tires.

Click to expand...

Ahhh ok, I didn't know it would make that big of a difference, now does it matter between mud Terrain and all Terrain?

It just depends on what you're using it for, all terrains have a much quieter ride than the mud terrains, but I don't think there is any sort of notable mileage difference.