bogging down on take off

Red Green Jr · Jun 29, 2008

On my 78, whenever I would accelerate from a stop, I had to go really slow otherwise it would bog down and occasionally stall. It turns out I fixed it by mistake. When I was checking the spark, it was really weak, so I looked in the distributor and noticed it was all rusted and corroded. So I got a new one, I had a **** of a time getting the old one out and installing the new one, but I noticed that on the old one, the vacuum that advances the spark was seized solid. So whenever I would accelerate, it would pour on the gas but the distributor was still spinning at idle speed so the spark was lagging behind. After I got the new distributor in, I went for a test drive and it was amazing, the throttle response was unbelievable! I figured this might be a fairly common problem so if your truck bogs down a lot or has bad throttle response, check your distributor.

BroncoJoe19 · Jun 29, 2008

Red_Green_Jr,

Thaks for taking the time to post helpful information like you did above.

Please allow me to help fill this thread out a little bit more.

A little CYA here... be sure that you are not wearing any loose clothing or jewelry that can get caught in anything when you are looking or leaning into an engine compartment with it running.

How to check the vacuum advance (at least what I know about it) with the engine running, from inside the engine compartment, goose the throttle, and watch the actuator portion of the vacuum advance. You should see it move. if it does not, you either have a vacuum leak, or a broken diaphram in the advance.

Also, another thing that could give a hessitation in a carbureted system, would be a funky accellerator pump. Normally when one looks into the throat of the carb, and if he/she pumps the throttle, one will see a squirt of gas get shot into the carb throat. IF not, that is a good sign that the accellerator pump is shot and needs to be replaced. It would be part of a rebuild kit, but I imagine that it can be obtained separately.

In both the older broncos, and the newer ones, a vacuum leak make be a cause for hessitation/bogging down on take off.

Innsufficient fuel supply is another (primarily the accellerator pump as described above).

Improper base ignition timing is another.

in the newer ones, the TPS (Throttle position sensor) would be the first thing I would suspect, but first thing I would do is check for vacuum leaks, and pull codes.

Johnny Reb · Dec 29, 2008

BroncoJoe19 said:
Red_Green_Jr,Thaks for taking the time to post helpful information like you did above.

Please allow me to help fill this thread out a little bit more.

A little CYA here... be sure that you are not wearing any loose clothing or jewelry that can get caught in anything when you are looking or leaning into an engine compartment with it running.

How to check the vacuum advance (at least what I know about it) with the engine running, from inside the engine compartment, goose the throttle, and watch the actuator portion of the vacuum advance. You should see it move. if it does not, you either have a vacuum leak, or a broken diaphram in the advance.

Also, another thing that could give a hessitation in a carbureted system, would be a funky accellerator pump. Normally when one looks into the throat of the carb, and if he/she pumps the throttle, one will see a squirt of gas get shot into the carb throat. IF not, that is a good sign that the accellerator pump is shot and needs to be replaced. It would be part of a rebuild kit, but I imagine that it can be obtained separately.

In both the older broncos, and the newer ones, a vacuum leak make be a cause for hessitation/bogging down on take off.

Innsufficient fuel supply is another (primarily the accellerator pump as described above).

Improper base ignition timing is another.

in the newer ones, the TPS (Throttle position sensor) would be the first thing I would suspect, but first thing I would do is check for vacuum leaks, and pull codes.

bogging down on take off

Red Green Jr

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BroncoJoe19

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Johnny Reb

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