Cursed with the bucking 2.9L


Jakeb86B2

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Hey guys my name is Jake, and I am new to this forum. I just bought (3 days ago) an 86 Bronco 2 4x4 manual 5 speed. Truck runs great at idle.

Here are the symptoms I'm dealing with.

• bucking on anything more than 1/8 throttle
• lack of power above 3000 rpms
• bogging at freeway speeds past 1/8 throttle (3rd-5th gear)
• all around PITA

Here are the parts I've replaced

• fuel pump
• plugs, coil, (wires are okay)
• distributor, cap, rotor, tfi module
• O2 sensor
• junkyard ECM out of an 89 ranger 5 speed 2.9

I have been reading these forms for two days and i think I have my timing correct but the tfi module is pointing straight back and before I swapped out the distributor (still had the bucking issue before the swap) the plug in connection for the tfi was pointing towards the passenger side.
Firing order is correct, truck idles great just a bit high. I put the engine on #1 compression Stroke. Pointed the dizzy/rotor at the number one plug on the distributor cap.

I'm at a loss for ideas paid 1000$ for the truck and sold my daily. Soooo this thing needs to run correctly.

It feels like it's Lossing fuel pressure under Full throttle, in first and second gear it will fall on it's face if I floor it but fine if I barely touch the gas pedal.

I could really use some help. I don't have and can't afford a multimeter right now to test ohms and such.
 


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Nez'sRanger

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My 2.9 was pretty similar when I first got it... From personal experience, I'd recommend changing the fuel filter, fuel pressure regulator, and the injectors... They're 33 years old, and most likely aren't functioning well. Especially the filter. If it's starving for fuel, it's not going to respond well to opening up the throttle and putting tons of air in the cylinders. You might want to run some fuel system cleaners through after you change the filter.
You'll also want to check the throttle cable... It's more likely than not stretched, and won't allow full acceleration even when everything is in tip top shape. There is a tech article about fixing it.
Apparently, the 2.9 has weak 4th and 5th gears, but 1-3 are (should be) absolute beasts.
Keep at it, it'll take some time, money, and a nice dose of frustration to get it operating pain free, but I and many others would say it's well worth it!
 

Paulos

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It could be a number of things. I would consider clogged injectors/fuel system first, or maybe even a bad MAP sensor. Have you pulled trouble codes? Fuel pressure test with KOEO and KOER? My '87 acted in a similar way for a while, and I threw a lot of new parts at it, including rebuilding the entire fuel system, except for the injectors. Replacing the injectors definitely fixed the problem. Ethanol has a tendency to kill the fuel injection system in these old Rangers if they sit for any length of time. Especially if the fuel is exposed to the humidity in the air due to a bad or no gas cap. Rebuilt injectors usually run around $12 each.

You'll probably have a code 95 due to that '89 ECM in your '86. You need to run a wire from pin 8 of the ECM to the hot (line, input) side of the inertia switch if you're going to keep using it. Unplugging the EGR Solenoid, the EGR position sensor, the knock sensor, and removing the vacuum line that feeds the vacuum reservoir is probably a good idea if you're using the '89 ECM also. Putting a thin blank shim between the intake and the EGR valve would be a good idea also, if the EGR valve doesn't fully seal.
 

Jakeb86B2

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Thank you Nez'sRanger I will try those, I feel like an idiot because I put the fuel filter back when I first went to AutoZone for this issue 🤦‍♂️
 

Jakeb86B2

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Paulos, correction it's an 87 ranger ECM.
And no I haven't checked codes as I'm not sure how with this old thing 😣 I know where the connection is under the hood, maybe I'll go and buy one of those easy OBD1 readers from the parts store.
 

Paulos

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Check with your parts stores to see if they can read the codes for you. I have heard that some will.
Believe me, you can throw parts at that thing all day, every day, and get nowhere but closer to the poor house :). I threw parts at mine for a year and got basically nowhere until I first cleaned the injectors myself (more money), and then, when that was only a 90% improvement, I broke down and bought new injectors, which solved the problem.

The good news is, my Ranger runs a lot better, I have all new ignition and emission parts/sensors, and some good new spares :).
Looking back, I would have been better off taking the truck to a mechanic to at least diagnose the thing (or perhaps, push it over the nearest cliff). I'm a decent mechanic, but my lack of fuel injection system knowledge cost me a lot of time, money, and embarrassment as my truck bucked and surged and smoked to work and back every day.
 

Jakeb86B2

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Okay guys, finally got the distributor in the correct place.....lots of fun on the side of the California 805 South in rush hour. But it's there now. Anyway fired it up and limped it to the next exit and parked it. Had my GF come pick me up with the trusty bugeye WRX.

I noticed while I was turning the distributor with KOEO the high pressure fuel pump would kick on and prime....don't think that's normal. Almost like it was hitting a switch
and with key in the on position turning the dizzy would actually Activate the starter for a brief terrifying second.

Anyway going to do a fuel pressure test tomorrow. I have the cartridge type fuel filter on the truck too it seems. Is there another one further back??? Like the cylindrical regular type?

On a side note while it is running all the injectors are firing. Verified with a long flathead screwdriver placed on each injector and placed the other end on my ear.

The sending unit was recently replaced along with the in-tank pump but I'm not sure I'm getting that pump to actually work. Will verify tomorrow for sure. That could definitely be the cause of all the damn issues. 🤬😤

How does one conduct a Fuel pressure test on the 2.9? I'm assuming just the valve on the fuel rail right?
 

rusty ol ranger

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My credo
A legend to the old man, a hero to the child...
Yup. Thru the valve on the fuel rail. 40psi is spec.

But if you got starters engageing and fuel pumps priming while your playing with the distributor, you got wirein issues.
 

Jakeb86B2

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I wish I could upload a video but every damn file is to big
 

Nez'sRanger

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Might have to put it on you tube and post a link to it.
 

Jakeb86B2

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Thanks everyone for your help, pulled the cartridge fuel filter and it was absolutely disgusting!!! A solid 1/4" of rusty goo/gunk all the way around it allowing no fuel to get through. Put a new one in and drove 100 miles pulled that one and it was still pretty dirty. But the truck runs worlds differently now

I think I'm going to order a new fuel tank after looking in the one that's currently in the truck. All I can find is 23 gallon tanks which I believe is the OEM size. But 45$ filled it from empty which is only 11.5 gallons 🤷‍♂️🤷‍♂️🤷‍♂️ could the tank really bad that effed up and full of crud? It has a new sending unit in it.
 

tSecurity

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Sounds like something in your tank definitely.
 

gaz

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Jake,

The BII 23 gl tank and the optional Ranger behind the axle tank are near the same shape, though the Ranger's rear tank is a mere 12 gl. Perhaps a former owner installed the optional Ranger tank?

When I 1st started reading your post, all I could think was vacuum, so please go through your lines and fittings.

The next thought I had was, is this chap disconnecting his distribution "pigtail", with a warmed up engine while he is adjusting his base timing???
 


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