Bronco II sputtering and no power

[ScarletStang]

Hi folks,
I am extremely frustrated with my 1989 Bronco II with the 2.9 engine(5 speed manual 4wd manual hubs & transfer case if that matters). It was 100% fine one day, then literally the next day it wasn't. When accelerating it's sputtering and losing all power. It Usually starts and idles fine(some times with a noticeable miss), but once I start to accelerate it starts sputtering, and if I push the throttle more it stops sputtering and completely cuts out. Also backfiring through the intake. I let off the throttle it resumes running, but will resume sputtering when given throttle again. It progressively gets worse the longer it runs, then it idles really rough touch the throttle and it dies. Don't touch the throttle and the rpms slowly go down till it dies. Some times you start it back up and it idle fine till you try to drive. When it's sputtering there's a smell, I want to describe it at raw fuel but not quite.
I changed the fuel filter then removed, tested and cleaned the injectors to no avail. Went on to the TPS and tested it with a multi-meter and it tested fine. Checked to see if the distributor was loose and it wasn't. Changed the TFI, plugs, new plug wires, new coil, and replaced the profile ignition pickup(PIP) in the distributor, no dice. Cap an rotor still looked fine. I read on another forum about a 2.9 with similar symptoms, someone suggestred to unplug the O2 sensor and see if it went away. I tried this too with no change.

These are the codes I'm getting(if I'm interpreting it correct)
6
7
6
7
Pause
1
Pause
4
1 - System Lean
Pause
9
6 - Fuel pump monitor circuit shows no power
Pause
4
1
Pause
9
6

Please any help would be appreciated. I really love this little Bronco, but it's driving me insane.
-Wesley

 

[DirtBronco]

This would be better in the 2.9 threads.

It sounds like your fuel pump in need of attention and the engine is leaning from fuel starvation. Hence the cutting out under throttle. Flapper opens, too much air/not enough fuel, stall.

Your ‘89 should only have 1 pump, in the tank. It’s not that hard to replace, just tedious. Might be a good idea to once over the underside wiring as well.

I would bet the filter sock either fell off and or has straight up disintegrated and some sediment flew up the intake. Check the tank for rust while it’s out. You may need a new one. It’s an old vehicle.

Exact same symptoms occurred on mine and a new pump drastically improved the performance until i realized my block was cracked.

 

[ScarletStang]

This would be better in the 2.9 threads.

It sounds like your fuel pump in need of attention and the engine is leaning from fuel starvation. Hence the cutting out under throttle. Flapper opens, too much air/not enough fuel, stall.

Your ‘89 should only have 1 pump, in the tank. It’s not that hard to replace, just tedious. Might be a good idea to once over the underside wiring as well.

I would bet the filter sock either fell off and or has straight up disintegrated and some sediment flew up the intake. Check the tank for rust while it’s out. You may need a new one. It’s an old vehicle.

Exact same symptoms occurred on mine and a new pump drastically improved the performance until i realized my block was cracked.

Thank you for your reply. And sorry you cracked your block, man.

I thought about the fuel pump possible being weak, but ever time I pressed the schrader valve on the fuel rail, the gas would hit the under side of the hood. Yeah, it's only got the one high pressure pump in the tank.

I bought a new cap and rotor last night and if that makes no difference, I'm gonna go ahead and drop the tank. Which is kind of a PITA, it's got the skid plate and a class 3 hitch in the way. I had it out earlier this year to replace the fuel float. I seen a little rust in the tank, but not enough that I wanted to mess with. I also replaced the fuel sock while I was in there. I probably should have done the fuel pump too.

New fuel pump will be my next course of action, But if anyone else has anything to add on, I'd love to hear it.

Also how can I move this to the 2.9 threads without assistance from an admin?

 

[DirtBronco]

Your best bet is PM'ing an admin.

The skid plate and definitely annoying. I left both of them off after the first time removing. Save the weight for something useful lol

If you have time, get the rust out with a kit from walmart. Definitely something you don't want oxidizing with your fuel.

 

[gaz]

When my Dakota exhibited the same symptoms, it was the MAP sensor had gone out.

 

[rusty ol ranger]

It defiantly sounds like its leaning out.

Get yourself a fuel pressure gauge and check the fuel pressure.

 

[ScarletStang]

When my Dakota exhibited the same symptoms, it was the MAP sensor had gone out.

Thanks for the input. Do the Ford 2.9s have map sensors? I know they're speed density and not MAF.

It defiantly sounds like its leaning out.

Get yourself a fuel pressure gauge and check the fuel pressure.

I think you're right. I got it to sputter while sitting still by holding the throttle open. I pressed the schrader valve on the fuel rail and there was very little pressure and the engine immediately died.

As of right now, I'm cleaning the rust out of the tank(it's worse than I remembered), the new fuel sock I put in earlier this year with the new float looks like it's stopped up. Also the fuel pump looks like the original, so I'll replace it and cross my fingers.

 

[JerryC]

You have a lean code, did you check for vacuum leaks?

Define what you mean by "backfiring". Can you see fire, hear the bang? If so, then you most likely have a jumped timing chain, but it could be a bad intake valve or valves or both.

 

[DirtBronco]

Can you see fire, hear the bang? If so, then you most likely have a jumped timing chain, but it could be a bad intake valve or valves or both.

Plus 1 on checking the valves if the new pump doesn't fully fix the problem.

 

[ScarletStang]

You have a lean code, did you check for vacuum leaks?

Define what you mean by "backfiring". Can you see fire, hear the bang? If so, then you most likely have a jumped timing chain, but it could be a bad intake valve or valves or both.

I have done a basic visual inspection on all the vacuum lines, but not an actual test using carb cleaner or propane.

There's a loud popping coming from the intake when it starts sputtering. It makes the whole air box jump when it pops. I removed the intake tube from the air box and it's about as loud as a 22lr.

I don't believe it's a valve, I neglected to mention I did a compression test when I did the plugs.
Passenger side front to back:
185
190
175
Drivers side front to back:
180
170
180

But jumped timing chain is a possibility I didn't want to think about.

 

[JerryC]

There's an old diag we used back when I was young to get an idea of how bad the timing chain was.
Pulling the spark plugs will make this easier.
Pull the distributor cap so you see the rotor.
Bring the engine around so you can see the timing marks and stop.
Now watch the rotor as you rotate the engine in the opposite direction stop when the rotor moves and look at the timing marks.
This will show how much slop the chain has in it. A couple of degrees is ok, several is not good, more is ugly.

 

[rusty ol ranger]

I have done a basic visual inspection on all the vacuum lines, but not an actual test using carb cleaner or propane.

There's a loud popping coming from the intake when it starts sputtering. It makes the whole air box jump when it pops. I removed the intake tube from the air box and it's about as loud as a 22lr.

I don't believe it's a valve, I neglected to mention I did a compression test when I did the plugs.
Passenger side front to back:
185
190
175
Drivers side front to back:
180
170
180

But jumped timing chain is a possibility I didn't want to think about.

At those compression numbers you can pretty much rule out anything valve/timing related.

Super lean condtions can cause the popping you describe, replace the pump, filter, and probably tank and go from there.

 

[gaz]

Yes, the MAP sensor is near the firewall just to right of upper intake manifold.

 

[gaz]

The MAP sensor is near the firewall to the right of the upper intake manifold, at the rear hood line.

 

[JerryC]

As I was looking at this thread again a thought came to mind.
Make sure you have the firing order correct. A couple of crossed up plug wires could cause your sputtering and backfiring.