1985 Ford Bronco stumbling on acceleration

RGUMNS

MEMBER
1985 FORD BRONCO

Engine Performance problem
1985 Ford Bronco V8 Four Wheel Drive Manual

My engine stumbles from idle to about 1500 RPM then smoothes out. It has little power until about 1500 RPM.
I have replaced the EGR valve and that didn't help. The problem has been steadily getting worse. I have been told many things from plugged fuel filter, to catalytic converter. I don't want to just throw money at it hoping to find the problem. It is also fuel injected with the 302 engine

4 Replies

SERVICE WRITER

MECHANIC
9,123 POSTS

Need to start eliminating (finding) the source. When the problem happens, what is the fuel pressure. Hook a gauge up and run it to the windshield, tape it so it stays then drive it and watch for the pressure changing (or not changing ) when the problem happens.

https://www.2carpros.com/car_repair_video/test_fuel_injection_pressure.htm

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Friday, June 6th, 2008 AT 5:31 AM

THIS IS MIKE

MECHANIC
686 POSTS

Here are some more things to check.

Have you had your car scanned for trouble codes. There could be some sensors like the MAP sensor or coolant sensor that have failed.

You should check ignition timing, it may need to be advanced.

You can check for good compression in all your cyclinders. Low compression can be a problem.

How many miles since you did a major tuned up?
Fuel filters should be replaced regularly.

If you want to test the fuel pressure you will need to connect a guage to the fuel rail on your car. You may need to consult a technical repair manual for the exact location and what the recommended pressure should be. All cars have different requirements.

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Friday, June 20th, 2008 AT 12:33 PM

RGUMNS

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3 POSTS

Thanks for your additional info. The problem that I am having as far as checking the fuel pressure is that I cant find the fitting for the fuel pressure guage.I have checked the manuals that I have and it says nothing about the location of the fuel pressure fitting. I have checked both fuel rails and followed the fuel line down to the high pressure fuel pump with no luck. I also checked the timing and the plugs. The catalytic converter is ok and I dont have any air restrictions. I have also replaced the fuel filter. Any additional help would be greatly appreciated.

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Friday, June 20th, 2008 AT 7:04 PM

SERVICE WRITER

MECHANIC
9,123 POSTS

I found a couple tsb's that mention fuel injectors plugging from carbon build up. A can of seafoam may help this.

Another one made reference to an air by-pass valve being replaced (has it been changed? If not ignore this one.)

One more I found says, "Detonation (spark knock), hesitation, surge, stumble or poor fuel economy, may be caused by leaking or damaged vacuum lines."

If the engine vacuum harness -9E498- contacts hot EGR tube or exhaust manifold, the above drive concerns can result.

Visually inspect vacuum harness for improper routing and/or heat damage (i.E, burned or melted nylon tubing).

MAke sure vacuum harness is routed away from EGR tube and R.H. Exhaust manifold.

I could not locate any specific location for the test port other than it has one. Info can be poor at times.

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Wednesday, June 25th, 2008 AT 7:49 AM