hesitation on acceleration

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Jun 30, 2013 | 09:09 AM

miihere24

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From: Charleston

hesitation on acceleration

Hey,
I know this issue has been covered in a few threads, but my situation is a bit different so I thought I'd see what advice y'all have. When accelerating from a stop and at low speeds there is a hesitation; almost like it's going to die, but then doesn't.

It's an automatic 1970 Ford F100 5.0L 302 v8 c4 tranny 2wd

I have replaced:

carburetor (including fuel filter that attaches to carb, accelerator pump came new on the new carb & gasket)
distributor (points are gone, it's electronic ignition)
spark plugs
spark plug wires (upgraded to 8mm)
oil & filter
anti-freeze (including thermostat)
transmission filter/gasket
transmission fluid (non-synthetic)
gas tank (did not replace sending unit)
water pump
fan belt
air filter (the housing is stock and the top doesn't close as tight as I'd like it too - going to replace it with an edelbrock 14" x 3" filter and housing)
Oil cap is new & hose leading from oil cap to air filter housing
Throttle return spring

I know some of those things don't correlate with my issue, but I just wanted to put it all out there. I do know that I don't have a stock throttle arm.

http://www.fordification.com/images/...tleLinkage.jpg

I only have the upper arm without the trapeze lower bit. That about covers it all. Any suggestions??

Jun 30, 2013 | 11:04 AM

elgemcdlf

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From: Alton, MO

Still sounds like accelerator pump. Could be timing though. How much slop do you have in your timing chain?

Jun 30, 2013 | 11:30 AM

miihere24

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From: Charleston

The timing was adjusted when the new distributor was put in. As for an actual chain...no idea where that would be to check it. I read adjusting the timing is a good way to know if you have too much slack in the chain. The timing has been looked at by 3 different mechanics over the past few months while I had the work done. It was adjusted once prematurely (before new distributor) and again after. Both timing marks were nearly over lapping.

Jun 30, 2013 | 01:44 PM

elgemcdlf

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From: Alton, MO

Checking the slop is easy. Roll the engine to 0. Then roll it back until you feel resistance. Check how much you changed in degrees. This will tell you timing slop in degrees

Jul 1, 2013 | 11:46 AM

Freightrain

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Joined: Jan 2003

Posts: 9,893

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From: Ohio

All the Autolites I've ever had stumbled like you describe. The poor design of the linkage for the accel pump made them difficult to work correctly(for very long).

Get under the hood, work the throttle linkage with your hand(quickly snap it open) and watch the accel pump linkage on the front of the carb. You will see that it doesn't always pump fully(or it is very slowly to react).

If you look closely down at the throttle shaft, just at the edge where it goes into the body of the carb, you will see a spring wound around it. This spring is what moves the accel pump arm. As you work the throttle, the spring then follows your motion and pulls the accel arm to pump fuel. Spray some WD40 on the spring area and see if that loosens it up and makes it work better(quicker). If that area gets gummy, it will be slow to react to your throttle input and thus cause a stumble.

This design flaw is the reason I throw them away ASAP. You can get them to work okay for awhile, but the stumble always comes back.

Jul 2, 2013 | 07:53 PM

JEFFFAFA

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From: Phoenix, Az.

Quote:

Originally Posted by elgemcdlf

Checking the slop is easy. Roll the engine to 0. Then roll it back until you feel resistance. Check how much you changed in degrees. This will tell you timing slop in degrees

This way or you can check it with your timing light. Both at idle and around 1200 RPM watch the timing mark with your light. If the chain is good the timing mark will not bounce around. If it is bad the mark will bounce around the amount of degrees it is bad.

Jul 3, 2013 | 06:02 AM

miihere24

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Joined: Apr 2013

Posts: 191

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From: Charleston

Hey, thanks for all that. I will have the timing chain checked with a timing light and try the wd-40. I have noticed the problem doesnt seem to be as bad while the engine warms up and have recently put fuel cleaner with some new gas, it might be in my head but it seems like that has helped. What does that tell me? Clean the fuel lines or replace? Check the fuel pump? When I starts to experience the hesitation I mash the gas harder and it lags for a split second and then takes off fine.