Sticking Throttle... What's wrong?

[ProjectPurity]

Hey, i've had an 81 rabbit for a while now, and it's always had a problem where the throttle will not drop the whole way when switching gears or putting it in neutral. The problem has worsened over time. to the point where i can be at regular idle, put the gas in a little and it will not drop AT ALL whereas it used to eventually return.

I've entertained the idea of it being one of the springs on the IP. I've entertained the idea that it's "running away" but since i'm venting the crankcase and the valve cover, i don't think it's due to blowby. The injectors have been removed recently, cleaned, and reinstalled after re-setting the heat shields. I'm not sure if they are problematic or not, haven't really thought about them that much.  I've also read around this forum and a "residual fuel screw" seems like it could also be the problem.

Oh, one more thing, if it's stuck at 1/4 throttle (for the sake of things i'm saying 1/8 is idle), i can knock it back to 1/8th throttle (idle) by sticking it in gear and letting out the clutch to bog it down a little.

What could this be?

Thanks,
JB

[Doug]

Does the throttle arm move back to the physical screw stop on top of the injection pump? Sometimes the spring assembly gets dirty and rusty enough to hang up. Lube and work it well. Check your cold start lever to see that the same situation is not occurring. Remove the throttle cable to see if it is moving easily within its sheath. Satisfy yourself that there is no external problem that is age and dirt related before you start to tinker with the pump internals.

[somolovitch3]

Don't think it is a "throttle" problem at all.

Sounds like a pump problem. (Know you did not want to hear that!)  :twisted:

You can back the idle scew way down, proble won't change the "runaway" all that much if at all. :roll:

My 79 Rabitt did the same thing. I bult a "kill" switch to mount on the shifter. It (via a normaly closed relay) opened the fuel valve's power feed, thus momentarily "killing" the engine to reduce the Revs.

Made shifting a lot easier, and was a great way to go down hills without using the brakes all that much. Just watch the Revs.

My 81 caddy had the same problem to the point of actually running away. :oops:
Ended up getting the pump rebuilt and timed.
Took care of the problem and the running away.

Good luck. :twisted:

[rubadubdub]

Quick and easy check to see if its pump or cable related: Pull lever on the top of the pump with the accelerator cable still attached (and presumably the revs will hang). Now remove the cable and recheck. If its the cable thats sticky then the revs shouldnt hang with it detached. If it does then it must be something on the pump.

Theres a black arm attached to the pump accelerator lever which ive been told is responsible for damping down the effects of the spring so the revs dont snap back down really quickly when you take your foot off the peddle. On mine you could move the position slightly so it has slightly more/less travel and therefore alters damping effect. Although when I tried it on mine and it didnt do anything!

Failing that blast the spring with WD40 working it back and forth, using that little red plastic tube to get it right into the nooks and crannies. I asked about this a while back and got some advice on how to remove the spring but i never needed to do it in the end. Search 'sticky gack in the throttle' or something similar, if memory serves.

Probably worthwhile ruling out the simple easy to check stuff before fiddling with the pump.

FYI mine was worse when cold and got better once warmed up, congealed oily gunk maybe? I could also pull the revs down by hooking my foot under the accelerator pedal and pulling it up. This suggested to me it was something sticking and not returning to position rather than something internal to the pump.