Popping at high idle, no power

BroncoJesseJames

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Oct 15, 2020
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Ok, here we go...My bronco starts easy, runs ok at idle, but will after a short while start to stall. if kept running(play with gas pedal), it will smooth back out then cycle through the stall/smooth. At high rpm it will pop through intake ( it will only run at high rpm when the idle is smooth). But there is no power trying to drive (warm or cold). Fuel pressure is good, fuel regulator tested, seems fine, EGR tested good. New injectors. Any thoughts? It has 5.0L and is a 94
 
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Tiha

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Jul 22, 2020
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Check for vacuum leak?

Fuel pressure is good while it is acting up?

Ignition module then, would be my best guess.
 

Skitter302

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Those are some good guesse, I was thinking the pick up inside the distributer.
 

pltommyo

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Is this running the old-style SD EFI or is it the "modern" MAF EFI? If SD, any mods to airflow would cause issues like that.
 

GunnySutton

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Ok, here we go...My bronco starts easy, runs ok at idle, but will after a short while start to stall. if kept running(play with gas pedal), it will smooth back out then cycle through the stall/smooth. At high rpm it will pop through intake ( it will only run at high rpm when the idle is smooth). But there is no power trying to drive (warm or cold). Fuel pressure is good, fuel regulator tested, seems fine, EGR tested good. New injectors. Any thoughts? It has 5.0L and is a 96
I would replace the fuel pressure regulator. Mine tested fine and it was the problem in the end. Cheap start and only three screws to replace.
 

Jasgeer

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Ok, here we go...My bronco starts easy, runs ok at idle, but will after a short while start to stall. if kept running(play with gas pedal), it will smooth back out then cycle through the stall/smooth. At high rpm it will pop through intake ( it will only run at high rpm when the idle is smooth). But there is no power trying to drive (warm or cold). Fuel pressure is good, fuel regulator tested, seems fine, EGR tested good. New injectors. Any thoughts? It has 5.0L and is a 96
"Pop through the Intake" could imply exhaust in the intake would shoot fears through me that an intake valve is leaking. By all means start by measuring intake vacuum. If it idles at >15 inches and is regular then celebrate that the intake valves appear to be sealing. From my experience the valve guides on 302s seem to wear and valve problems develop. Lack of power indeed could be related to fuel pressure or ignition.

How many miles are on the engine?
 

BroncoJesseJames

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Oct 15, 2020
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"Pop through the Intake" could imply exhaust in the intake would shoot fears through me that an intake valve is leaking. By all means start by measuring intake vacuum. If it idles at >15 inches and is regular then celebrate that the intake valves appear to be sealing. From my experience the valve guides on 302s seem to wear and valve problems develop. Lack of power indeed could be related to fuel pressure or ignition.

How many miles are on the engine?
The mileage reads 125,000, but I don't feel that it is correct. There is also at least one dead cylinder. I was leaning toward a bad cam lobe...but have not tested valve movement or vacuum on the intake.
 
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Jasgeer

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The mileage reads 125,000, but I don't feel that it is correct. There is also at least one dead cylinder. I was leaning toward a bad cam lobe...but have not tested valve movement or vacuum on the intake.
A 96 5.0 should have a roller cam. There is little chance of a bad cam lobe as cam wear is low unless something broke.
Better find out the cause of the dead cylinder.
 

Jasgeer

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Ford changed to the roller cam with 1985 302/5.0L engines. They unfortunately never tooled the 351 for a roller cam although several aftermarket cam companies offer roller setups for the 351. It allowed significantly more HP because the 'integrated value' of the valves being open is much higher. The ramps that open and close the valves can be much steeper/faster for a roller follower than a flat tappet.
 

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