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Thread: Engine Rough Idles after hard brake

  1. #1

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    Post Engine Rough Idles after hard brake

    Hey All,
    So I have had this truck or a few year now and its always had a problem where if I brake hard/firm braking, RPMs will drop to like low 200s/ almost stall. Revving the engine remedies the issue a it idles normal.
    I believe its called "back pressure" but I have no idea how too fix it. Thanks in advance!

  2. #2

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    I'd check the vacuum line and check valve to the brake booster. If the hoses aren't a firm fit to all of the barbs, it could pull air under high vacuum. You should get a couple of good pumps on the brakes without experiencing issues under normal circumstances.
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  3. #3




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    It could also be an improper float setting in the carb - if set wrong or bad, hard braking could sent it to a point that the needle valve shuts off the gas to the motor. What carb do you have?
    Pennyman1
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  4. #4

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    Quote Originally Posted by pennyman1 View Post
    It could also be an improper float setting in the carb - if set wrong or bad, hard braking could sent it to a point that the needle valve shuts off the gas to the motor. What carb do you have?
    Its a Weber I installed right after I bought it.

  5. #5

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    I will check that. Thanks!

  6. #6

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    when I bought my truck, my weber was installed with the fuel bowl towards the fire wall. It would do the same thing under heavy braking or just pointed down a steep hill. I remounted the carb with the fuel bowl towards the front of the truck and the problem went away. The fuel bowl should always be mounted towards the front. This will enrich the mixture when going up hill or accelerating hard, and lean it under heavy braking or coasting downhill. When it's mounted backwards, the fuel level in the float bowl is effectively raised under hard braking or pointing downhill, and it will flood the engine enough to make it sputter pretty hard or stall.

  7. #7

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    Quote Originally Posted by Giovanni89 View Post
    when I bought my truck, my weber was installed with the fuel bowl towards the fire wall. It would do the same thing under heavy braking or just pointed down a steep hill. I remounted the carb with the fuel bowl towards the front of the truck and the problem went away. The fuel bowl should always be mounted towards the front. This will enrich the mixture when going up hill or accelerating hard, and lean it under heavy braking or coasting downhill. When it's mounted backwards, the fuel level in the float bowl is effectively raised under hard braking or pointing downhill, and it will flood the engine enough to make it sputter pretty hard or stall.
    I might have to do that myself, because I work on top of a mountain and extreme uphill/downhill is going to be an everyday thing. lol

    Did you have to lengthen the brake booster line when you flipped the Weber around? That and the throttle linkage might get a little weird...

  8. #8

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    Whoever installed my weber put a separate take off on the throttle pedal for the kick down cable. I forgot that most people have the linkage mounted on intake to the kickdown. I flipped the throttle cable so that it comes out of the firewall headed towards the drivers fender. I had to lessen the bend in the steel portion at the beginning of the throttle cable to clear the booster. Didn't have to touch the booster hose, but I don't think my booster hose is oem. Basically the throttle cable points towards the drivers side fender and does a gentle u turn. Been that way for 60k miles. No problems with the cable binding.
    Quote Originally Posted by WarStryker13 View Post
    I might have to do that myself, because I work on top of a mountain and extreme uphill/downhill is going to be an everyday thing. lol
    Did you have to lengthen the brake booster line when you flipped the Weber around? That and the throttle linkage might get a little weird...

  9. #9

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    I've got a manual, so I don't need to worry about the kickdown. Good to know for if I ever get an automatic...

    Thanks.

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