Car stuck accelerating

Hello so had a bad experience today while driving my cab (MK1 GTi 1.8 DX 1987 with K jetronic injection). Was taking the car out for the first time since November and it was running sweet like it used to but suddenly it revved up without warning so turned engine off and luckily I was only 4mins from home so pushed it back. Tried multiple times but as soon as I start the car it revs up and doesn't stop. Checked the cable on carburetor to see if it was stuck but nope even when the flap is in off position it still revs so don't think the problem is coming from the accelerator pedal. Could the problem be within the carburetor itself and the valve is stuck ? Any help would be appreciated

That's CIS not Carbed.
If the Cable is free, as you can take it off and the cable moves in and out freely then your issue may be with the cold start injector or WUR.

Of course you want to check and eliminate vacuum leaks.

Hello yes silly me meant the throttle body, could the flap be stuck open ?
Will look into the warm up regulator and I've changed the other 4 injectors but never the cold star injector I reckon it's never been changed and the car has 180k miles.
Will have a look into this weekend and see what I can find. How can I rule out the WUR from being faulty ?

There are tests outline in the Bentley.
Diesels and Digifant I know…cis not so much.

Ok so had a quick look today the flap (valve) of the throttle body is fine so that's not the issue. I don't think it could be from the accelerator cable because it works fine when i push the accelerator i can see from the inside the cable moving and opening closing the valve of the throttle body.

Note: After starting the car multiple times the revs stop at 3500-4000rpm and the problem happened all of a sudden after a bit of acceleration in 2nd gear at 4000rpm went to neutral to go into 3rd gear and then realised while in neutral car was revving for no reason

Just out of curiosity looked at the oil dipstick and it did smell a bit petroly. Gonna have another look tomorrow after work and just check the idle screw on the back of the throttle body to see if something is wrong (loose or rubber seal gone bad). If i can't find anything there, then might look into buying another injector for the cold start. I only know heritage parts so if anyone else has any good websites for buying golf parts that would be a great help.
 

Ok update I removed the connection to the 5th injector and the car struggled to start but did eventually and was still at 4krpm. So I doubt the 5th injector is at fault because even if it was stuck open it wouldn't have struggled as much to start it.
But on the other hand after inspecting and removing a load of pipes because they seemed dirty as if they were leaking I found this. Gonna order the parts and hopefully it should resolve the issue 🤞

 

Vacuum leaks are the bane of Dubhood.
Don't forget to test the rear of the throttle body there is a 7mm brass screw if it turns easily with your fingers the o-ring s bad.  Gimmee Wrap the Treads of the thing only the threads with Teflon tape.

Thanks for the quick reply i was able to slightly turn the brass screw by hand without tools, didn't want to touch it much in case i messed something up, should i order an o-ring for it ?

Yep. or take it out and get a new one at a hardware store.

Remember to wrape the threads with teflon tape.

place it back in, tighten it till it stops then back off about 3/4 turn.

Jon Hodgon said

 

What is the green connector hooked up to on the front of the throttle body? I have the same on mine but nothing is plugged into it…

Off the back of my head i can't remember what the green connector plugs into. I should receive the new 3 way hose I need tomorrow so I'll take a look while I'm there at my garage and let you know

Ok so just popped to the garage and replaced a couple of hoses and temporarily taped up the 3 way hose (new one arrives tomorrow) to see if it solved the issue and no…..
The car's idle is still 4000rpm which I doubt is because of air leaks now and more because something is stuck or open when it shouldn't be. Note that this happened while driving after a little acceleration at 4000-5000ish rpm.
Throttle flap is fine and free, the air flap above air filter is also free and moves by hand. The cold start injector when electrical connector is disconnected car struggles but eventually starts leading me to rule that out because if stuck open mechanically it would have been the same plugged or unplugged.

It's too dark to work now.
(Idea : Tomorrow will wind in the idle screw to the max and see if car starts, if the car manages to start then would that mean that it's getting air from somewhere else ??) Let me know if the idea is sound or pointless.
If anyone has any ideas let me know I'm all ears !
This is my very first project car btw so I'm new to the whole car world and a complete beginner. Car did run excellent last year FYI

Jon Hodgon said

Off the back of my head i can't remember what the green connector plugs into. I should receive the new 3 way hose I need tomorrow so I'll take a look while I'm there at my garage and let you know

Thanks - looks like it could be a throttle position sensor, I have the same on mine but the throttle body is from an audi 80 and there isn't anything standard on the mk1 engine to plug it into as far as I'm aware, so would be interesting to see how yours is set up…

Found this picture from another post it seems to go behind the throttle body it's not easy to see.

Tightening the idle screw didn't do anything because my car isn't idling but instantly accelerating so car doesn't get a chance to idle
Just an idea could my k jetronic system be faulty ???
Forcing my injectors to spray as if accelerating when they shouldn't be ?

Thanks, but trying to trace where the wire that is plugged into that is connected to..

Hope you sort your issue 

When it is running at it's high idle, does it sound okay?
K-jet is relatively simple in the principles of it's operation - as the throttle opens, more air is pulled past the air-flow plate, which in turn moves a small piston in the metering head to allow more fuel to the injectors. Vacuum leaks normally admit 'unmetered air' that is to say it has no impact on the air flow plate position, so you'd end up with a leaner mixture as you'll have more air than fuel.
On the back of the inlet manifold you'll find the Auxiallary air valve (AAV), this allows metered air past the throttle body on cold starts (it's basically a flap is open when cold and closes as the car warms up). If this is stuck open, it could be the issue.
Clamp the hose that comes out of the AAV (will come at the back of the inlet manifold, left hand side as you are facing the car, if you stand to the left of the engine you'll see it clearly) and see if that makes any difference.

I also have no idea what that switch on the throttle body does, it's not on my '83 k-jet. It may be worth unplugging that to see if it makes any difference. It's a microswitch that makes something happen, could be some kind of fuel enrichment at a more open throttle position…no idea.

That green connector on the throttle body I think has something to do with enrichening the mixture slightly when the engine is under acceleration and still cold, it may go to a switch that opens the fifth injector for a fraction of a second.
Your problem must be to do with an air leak, excess fuel would slow the engine down, what about the hose that goes to the brake servo, are the brakes okay
There are some one way valves in the system as well but I confess I don't fully understand how all that works.

I'm not free this weekend to work on the car so I'll get back to it on Tuesday. I did unplug the connector but it didn't do anything.

Your accel cable is a tad rusty.  I would remove it from the TB and spray it with TRI-Flow oil as it needs to be shiny, and slick.  Let it get in to the cable sheath I used to hold mine up with a piece of string tied to the bonnet, and let it slide its way down the entire cable.