Bronco Running Lean

[Agui-E7TE]

My Bronco appears to be running incredibly lean and is sputtering like crazy. It doesn't have any power and can only do about 35 mph on a flat road or smooth desert. 16 mph in soft sand. I thought it could be a plugged fuel filter so I removed it and blew through one end and it sprayed all the fuel out so it's not clogged there. I carry a spare frame rail fuel pump so I swapped it out and that didn't change anything either.

I'm stumped on this one and was hoping maybe someone on here might have seen this issue before. My Bronco is an '89 with a 5.8 and a C6.

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Here's how my misfortune adventure started.

I took my Bronco out to Ocotillo over the weekend and everything was running awesome until we started idling through trails and my water temp started climbing. It came back down once we got rolling again but then I really started beating on it on loose dirt hill climbs and on one particular hill it seemed to loose power halfway up the hill. I was pinned at WOT in 4-Low in 1st gear and it felt like i didn't have enough fuel. I still have stock gears (3.55s) and a C6. I didn't think much of it because my fuel level was pretty low (like close to empty).

I drove it about another 20 miles but my tranny was puking so I took it easy and made it to the road but not before pushing it on the last long hill climb. I let it cool down for almost an hour and filled the tranny with 3 quarts of ATF and filled the radiator with water.


We headed out on the road for 15 miles to get gas and everything was fine. Filled the tank ($117) and then took off on the road and about 5 minutes into the drive it started loosing power. it felt like I had to let up on the throttle to get it to go down the highway. It got so bad I could only do 45 on the highway and I pulled over to see what was wrong near Highway 8 by the border. After having no luck finding the problem, we decided to hit the dirt for the next 30 miles and my average speed was probably about 30 mph until I got back to camp off of Highway 78 and Split Mountain Road.

The next day I checked the fuel filter and when it checked out I swapped to my spare fuel pump and it stayed the same. Decided to drive it to the big gas station in Salton City and that was interesting trying to maintain 35 mph most of the way. With a tailwind I got as high as 50 but had to pull off into the shoulder and ride the whoops while a truck and trailer passed me on 78. Had to get it towed from Salton City to a buddy's house in Yucaipa.

It was a long day and night but the trip sure was a blast.

[SteveG]

Did you take a fuel pressure reading?

[Agui-E7TE]

Hey Steve! No, I didn't. I don't have a fuel pressure tester and I was in the desert when this happened. I will most likely look into buying a tester to see what it's reading. Only problem is the truck is 60 miles from me right now. My plan was to go back with a new O2 sensor, new coolant temp sensor and a new map sensor to see if just maybe I can get lucky.


I've heard there is a low pressure in tank pump but I've also heard that if it stops working the rail pump wont suck any fuel out either way but I don't know if any of this is true or not.

[Rmc]

Possibly stuck open egr valve? That would choke it up pretty bad but fuel starvation is usually solid idle shitty acceleration. Well upon acceleration it's starts sputtering and puking. What about chunky felling like really hard shuddering? Torque convertor could be the culprit if that's the case, or possibly injector power issues? Just giving a few ideas for what it's worth.

[Agui-E7TE]

So my buddy was pulling it into his driveway and it died. This time it wouldn't start and it he said the distributor rotor was able to spin freely. I've had a roll pin go out on it in the past and I replaced it and that was over a year ago. Looks like the roll pin sheared again. everything else looks fine otherwise.

New plan is to upgrade to a different distributor but we're going to put a new roll pin in it and see what it does. My next plan is to upgrade the entire exhaust system. I will probably add Edelbrock headers and then I need to find out who makes an aftermarket exhaust pipe from the headers to the muffler with a CA smog legal cat on it. I'll throw a new O2 sensor at it and new plugs, cap, rotor and wires too because it only serves to improve it.

Stay tuned to see if my cats are plugged or not.

[Seabass]

Do you have a factory cam? What ever distributor you run make sure it has a factory ford gear on it. I'm sure you know but make sure you run the correct distributor as far as 5.0 vs 5.8

[Agui-E7TE]

I do have the factory camshaft. I'm all too familiar with the distributor issues. Learned this the hard way in my '79. The MSD Pro Billet distributor I used on it seems to be working fine over a year later and tons of miles on it.

Thanks for the heads up though.

[Phoenix0783]

O2 sensors or tps can cause a/f ratio issues.

[BDKW1]

Sheared gear pins? Check the oil pump...........

[Agui-E7TE]

What should I check specifically on the oil pump?

[BDKW1]

That it still turns...........


Every time I have had drive gear problems it has been the pump. Shearing a roll pin takes a shit load of force, a good running pump should never get anywhere near that much rotational force.

[Agui-E7TE]

So my buddy got the Bronco running right but he had to replace the distributor to oil pump shaft because it was bent. Not quite sure how it happened or how it even ran limping around at 30 mph for over 70 miles total, 30 of which were through desert that was full of sand and even some silt beds.

I'll post a photo when I get a chance.