Engine Stumbles when Cold

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Apr 1, 2003 | 04:04 PM

JJH

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From: Panama City United States

Engine Stumbles when Cold

I have a 84 f-150 with a 302 with 4 barrel Holley. The engine stumbles while accelerating until the engine gets up to temp. After that it does fine. Could this be a choke problem? If so any suggestions on adjustments would greatly appreciated.

JJH

Apr 1, 2003 | 07:36 PM

Franklin2

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From: Virginia

Engine Stumbles when Cold

Yep, sounds like the choke. I suppose it has a automatic choke. On a cold morning, take the air cleaner off, and push the throttle lever open with your hand. The choke door on top of the carb should shut completely. If it doesn't, look at the passenger side of the carb. You should see a large round black plastic thing. Loosen the screws a little that hold it on, and turn it while holding the throttle open. This adjusts how much tension is on the choke door. More tension equals more choke. It may take a few mornings to get it just the way you want it.

Apr 1, 2003 | 08:07 PM

JJH

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From: Panama City United States

Engine Stumbles when Cold

Thanks franklin2 i will try this. One question on the choke adjustment. You say to hold the throttle open while turning the round box on the other side, how much open? Wide open are just cracked open? Also the flap in the top of the carb should be completly closed right. After starting the engine should it open some? And does this affect how long it runs at 1500 rpm before it will turn loose and return to normal rpm. I am going to try it as soon as you let me know.

Thanks JJH

Apr 1, 2003 | 08:45 PM

Franklin2

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From: Virginia

Engine Stumbles when Cold

Hold the throttle pretty much wide open. This keeps the choke from hanging on the fast idle cam.

Also the flap in the top of the carb should be completely closed right. After starting the engine should it open some?

Yes it will completely close. After the engine first starts, the choke should crack open a little. This is called the choke pull off and is actuated by vacuum. Some carbs have a lever going to a vacuum can that you can see. I know some of the holleys have it built in behind the choke housing.

And does this affect how long it runs at 1500 rpm before it will turn loose and return to normal rpm?

Yes, it will affect the kickdown time. This will also be a clue as to what the choke is doing. It can kickdown to soon, and cause the stumbling. If the idle is too high for too long, then the choke is set too rich, or it's not functioning correctly.

Apr 1, 2003 | 08:54 PM

JJH

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From: Panama City United States

Engine Stumbles when Cold

I got ya! I'll give it a try and thanks for the quick reply!!

Thanks Again
JJH

Apr 6, 2003 | 05:33 PM

JJH

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From: Panama City United States

Engine Stumbles when Cold

Hey Franklin 2, I made the adjustment and that seemed to work but I have another question. The engine will not idle down until it is ready to idle down. Is there something that I can do to make the choke turn a loose when I am ready instead of waiting 5 minutes. THe engine is running to fast to put it in gear and blast off.

Thanks JJH

Apr 6, 2003 | 08:37 PM

Franklin2

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From: Virginia

Engine Stumbles when Cold

Do you have any heat assist going to the round black housing area? This would be an electrical wire connection, or a fitting on or near the housing with a steel line running down to the exhaust manifold, or a steel line running down through the intake manifold on the passenger side, and then running up to the aircleaner.

If you have one of these, they need to be working to help warm the housing, making the choke release faster. The steel line system should get warm(hot air from the exhaust warms the line into the housing) or the electrical line should have some voltage, and you should get continuity with a meter from the housing terminal to the carb metal(this style has a heating element inside the housing).

If all else fails, there is a fast idle adjustment screw on the passenger side of the carb, down behind the round housing. It's hard to see and get to, but it's there, and will adjust how high the fast idle is when the choke is on.