High Idle in Reverse Only

[vwman55]

I have a strange problem going on with my AS. Has been fine for the 8 or so years I have owned it. Here it is: this happens in reverse only, shift into reverse, press on the gas pedal, revs real high, have to pull it out of reverse to keep from smashing into something. Once I pull it out of reverse it idles back down. Tried blimping the throttle to idle down, no good. Doesn't happen in forward gears. Tried low gear only thinking that it was something to do with the low gearing. All hoses correct and connected. Replaced 12mm vacuum hose, from Belmetric, reinforced type. I thinking that it may be vacuum related. Pulling air back though the CV? Shifter points adjust related?
I don't know. Doesn't seem to happen if I pull into reverse and don't touch the gas and let it roll but, it's sort of a inconsistant problem. Can't think of anything different from reverse and forward geras except shift lever position. Any ideas? 

[Bookwus]

Hiya 55,

You hit the nail on the head with your description of this problem.

Strange indeed!

My first thought was a vacuum related problem also.  I can't see how the shift lever points would come into play here if the tranny stays in Reverse all during this "idle-up". 

Something here has to be at work getting more gas and air into the combustion chambers.  Since that's the carburetor's job, I'd start looking there and at the accelerator cable.

[68autobug]

Now that is an odd one...lol

in Reverse or LOW gear shouldn't be any difference..

Have some one put it in reverse and revving the engine

while You check out what is happening...

make sure the emergency hand brake is working..

I'd hate to hear You had been run over...

something very odd..??  is happening...
too much air being sucked into the carby or inlet manifold...??
causing the engine to rev ..
can't see how any extra fuel could be flowing??

if You think there is extra fuel flowing...
take the air cleaner off and look down the throat of the carby..
whilst standing on Your rear bumper...

best of Luck

LEE in Australia

[jaywiz]

mine was doing this when i first showed the wifey how to drive it,turns out the carpet was moving when she pushed down the shifter to go into reverse.It would wad up by the pedal if you didn't touch the gas it was fine but touch the pedal and you were racing backwards.I ended up velcroing  the carpet down.(never happened to me just her)

[68autobug]

mine was doing this when i first showed the wifey how to drive it,turns out the carpet was moving when she pushed down the shifter to go into reverse.It would wad up by the pedal if you didn't touch the gas it was fine but touch the pedal and you were racing backwards.I ended up velcroing  the carpet down.(never happened to me just her)

Excellent answer...
the carpet can cause problems...
I did have the  opposite problem...
My carpet would get behind the gas pedal  and stop the pedal from being pushed down... lol
Also only happened to My Wife,,, lol

I moved the carpet and underlay and also adjusted the accelerator cable on the carby...
so, the accelerator is much more responsive....

LEE

[vwman55]

There is something different from forward and reverse, has something to do with torque and the way the engine and trans are mounted together.
Anyone...............................................?

The trans torques the oppsite direction. It's lifting the left side of the trans up and off the broken trans mount, therefore pulling the accelerator cable tight causing the high idle.
Pull it out of reverse gear, torque removed, trans drops back down and returns to idle. Probably explains the shifting into reverse thumping I had for a while.

[68autobug]

There is something different from forward and reverse, has something to do with torque and the way the engine and trans are mounted together.
Anyone...............................................?

The trans torques the oppsite direction. It's lifting the left side of the trans up and off the broken trans mount, therefore pulling the accelerator cable tight causing the high idle.
Pull it out of reverse gear, torque removed, trans drops back down and returns to idle. Probably explains the shifting into reverse thumping I had for a while.

Hi
Now that is a good answer..??
My beetle used to lift up at the rear when reversing and using the hand brake..
My beetle has new engine mounts... and nothing wrong with the old ones..
so, I still think its the brakes... ??

LEE

[vwman55]

Hi Lee,
Not sure what the ?? means. You don't think that's what's happening?? Here's what I've looked at under the car. The throttle cable is attached to the top of the trans.
Goes through the tube and a nylon grommet anchored to the trans. That's where the pulling is coming from. I can push up on the left side heater box and see it lift the trans an inch.
My mounts are oil soaked and soft. Something else I've came across is 2 different lengths of throttle cable, 2650mm and 2642mm. About an 1/4" difference.
Don't know if that would provide enough slack and still allow WOT. Either way I don't think VW designed it to work that way. I mean if you weren't ready to pull this thing
out of gear you would smash into something pretty quickly. I did slack the cable with the 1/4" of the cable sticking out of the barrel and that provided a bit of headroom
before it sticks open. Could you explain the brake theory?
Anyway, your thoughts? Anyone's thoughts?
'73 SB A/S