Accelerator pedal resistance - 70 SS - Chevelle Tech
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post #1 of 20 (permalink) Old Mar 3rd, 19, 11:57 AM Thread Starter
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Duane
 
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Accelerator pedal resistance - 70 SS

I have an issue that has lft me scratching my head.
I have a 7040205 Qjet on my 70 SS with original big block.
The throttle seems to operate smoothly when I depress the gas pedal full range while the car is off.
However, when I go to punch it while driving down the road it seems to get a distinct resistance when getting to the point of the secondaries opening. I've checked the cable as best I can and cannot seems to find and areas where it would be binding. Like I said, when the car is shut off the pedal goes from top to floor without and noticeable difference but when the car is driving down the road, the pedal moves freely about 2/3's of the way and seems to bind slightly until you push through it and the car launches as the secondaries open.
What could I be missing?
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post #2 of 20 (permalink) Old Mar 3rd, 19, 12:02 PM
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autumngold
 
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Re: Accelerator pedal resistance - 70 SS

Wierd.Doesnt make sense unless your motor mounts are loose or worn causeing the motor to move when going.
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post #3 of 20 (permalink) Old Mar 3rd, 19, 5:34 PM
 
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Re: Accelerator pedal resistance - 70 SS

disconnect the cable from the carb , then move the throttle arm on the carb , then start it and see if it requires more effort

im guessing its something in the throttle plate binding while under vacuum
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post #4 of 20 (permalink) Old Mar 15th, 19, 10:45 AM Thread Starter
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Re: Accelerator pedal resistance - 70 SS

checked the motor mounts, all looks good. Move on to the next possible cause. I can't start it at the moment but that will be the next test.
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post #5 of 20 (permalink) Old Mar 15th, 19, 11:01 AM
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Re: Accelerator pedal resistance - 70 SS

Are you sure you have good electrical grounds on your car and that the battery/alternator aren't trying to ground through the accelerator cable?

I have found some horrible grounding situations going on because of ground cables going to brackets that weren't well grounded to the block, heads or intake manifold. The cure was to ground the battery directly to the block or head.
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post #6 of 20 (permalink) Old Mar 15th, 19, 11:45 AM
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Re: Accelerator pedal resistance - 70 SS

My carb linkage ball mount was rubbing the bottom of the air cleaner base as it swung straight up. I had to put a small dent in it.

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post #7 of 20 (permalink) Old Apr 6th, 19, 1:27 PM
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Re: Accelerator pedal resistance - 70 SS

Found that model Qjet is also called the R4-4MV. More info here including an exploded parts view.

My engine originally had a 4MV model, and I recall the vacuum diaphragm and lockout lever (parts 50-56 on the parts view) prevented the secondary throttle valve from opening when vacuum was high. This mechanism on the passenger side of the carb could be a cause for throttle binding during operation.
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post #8 of 20 (permalink) Old Apr 6th, 19, 1:50 PM
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Dan
 
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Re: Accelerator pedal resistance - 70 SS

Quote:
Originally Posted by duanec View Post
checked the motor mounts, all looks good. Move on to the next possible cause. I can't start it at the moment but that will be the next test.
When you can start it...open the hood, put in gear and give it some gas with brake on a bit more at a time and see if the motor mount or week motor mount is lifting on the drivers side.
Had a bad mount in a 69 impala back in the day and had similar issues as you until it finally broke...then while giving it gas going around a corner in would damn near give it full throttle= not good!
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post #9 of 20 (permalink) Old Apr 7th, 19, 11:20 AM
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Re: Accelerator pedal resistance - 70 SS

Quote:
Originally Posted by Malibu70 View Post
Found that model Qjet is also called the R4-4MV. More info here including an exploded parts view.

My engine originally had a 4MV model, and I recall the vacuum diaphragm and lockout lever (parts 50-56 on the parts view) prevented the secondary throttle valve from opening when vacuum was high. This mechanism on the passenger side of the carb could be a cause for throttle binding during operation.
This is where I'd be looking, especially since you feel resistance at the point where the secondaries are activated. I would also take it for a spin without the air cleaner.
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post #10 of 20 (permalink) Old Apr 8th, 19, 9:01 AM
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Re: Accelerator pedal resistance - 70 SS

I had a wiring harness making my gas pedal hang up once. Check it all out..
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post #11 of 20 (permalink) Old Apr 18th, 19, 8:42 AM Thread Starter
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Re: Accelerator pedal resistance - 70 SS

The motor mounts are solid. I should be able to get it out of the paint shop in about a month to try some of the other suggestions. Thanks!
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post #12 of 20 (permalink) Old Apr 18th, 19, 10:40 AM
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Re: Accelerator pedal resistance - 70 SS

Do you have any type of 4 hole spacer. If so - See if that is not binding somewhere. The one hole spacers not so much a problem as the hole is usually very large.
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post #13 of 20 (permalink) Old May 17th, 19, 3:55 PM Thread Starter
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Re: Accelerator pedal resistance - 70 SS

Quote:
Originally Posted by dyno jonn View Post
Are you sure you have good electrical grounds on your car and that the battery/alternator aren't trying to ground through the accelerator cable?

I have found some horrible grounding situations going on because of ground cables going to brackets that weren't well grounded to the block, heads or intake manifold. The cure was to ground the battery directly to the block or head.
Wow! I would never in a hundred years expect it to be a ground issue. I will definitely check that out.
Thanks for the feedback!
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post #14 of 20 (permalink) Old May 17th, 19, 3:56 PM Thread Starter
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Re: Accelerator pedal resistance - 70 SS

Quote:
Originally Posted by hydro462 View Post
I had a wiring harness making my gas pedal hang up once. Check it all out..
Another good suggestion. I'll inspect that. Thank you!
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post #15 of 20 (permalink) Old May 17th, 19, 3:58 PM Thread Starter
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Re: Accelerator pedal resistance - 70 SS

Quote:
Originally Posted by Lew540 View Post
Do you have any type of 4 hole spacer. If so - See if that is not binding somewhere. The one hole spacers not so much a problem as the hole is usually very large.
No spacer....except I do have that spongey thick-ish carb to manifold gasket. I'll have to check it out. Thanks!
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