Desperate for advice! Car stalls when braking, but not in reverse

Hi all,

I am really stumped by this issue and very desperate for any information that might help me.

I have just got a 93 Cabriolet (Manual transmission) thats been sitting in storage a while. It runs perfectly but for one thing: When I brake, even a little, the engine stops. No sputter or sudden power loss - it just cuts out like a kill switch has been pressed.

Weirdly enough, this does not happen when I use reverse.

I thought it might be the brake booster vacuum hose leak but the brakes feel fine and the issue does not occur when I brake in reverse. In fact I can lock up the wheels in reverse and the engine seems fine.

The engine cuts out when braking both in gear and in neutral.

The engine itself starts, accelerates and idles fine.

Ive cleaned the throttle body, distributor cap and replaced the old stale fuel with fresh fuel.

Other than that I dont know what else I can do at this point. Fuel pump relay, distributor coil?

Any help anyone can offer is much appreciated!

EDITS:

Here is a better video of the problem: https://www.youtube.com/watch?v=ec4wQ-8Oqy4

I've also crossed possible brake booster issues from my list. I disconnected the brake booster vacuum hoses altogether and tested - the problem still persists.

What I now think  guess is happening is the engine is flooding - something about that little jolt when you brake causes petrol to serge into the engine (no idea how this happens with injection) and the plugs get wet. Just a guess, but Im out of ideas.

Hi and welcome first of all.
To be honest I haven't go a clue as I've never heard that before on any car.   

But I'm confident we will have members here that will have and can tell you what to do!  

Stay tuned.  

Is it a carb model?

If so, I will put money on the carb rubber mount having a big split in it, on the rear side.

As you break, the weight of the carb causes it to tip forward, opening the crack in the rubber mount causing air to be sucked in after the carb, meaning no fuel is being added. Instant cut out…

Doesnt happen in reverse as the weight of the carb is applying pressure to the split side, keeping it sealed.

AL_Mk1 said

Is it a carb model?

No its the K-Jetronic injection. That being said, can what you described be applied to the injection unit as well?

I'll check if its loose.

meltingdog said

AL_Mk1 said

Is it a carb model?

No its the K-Jetronic injection.

Ah well…

No - The k-jet wouldn't suffer from this sort of issue as there are no "Rubber mounts" like I described above.

It is very odd that it happens going forwards, but not backwards. I think it could still be an issue with something moving, such as the whole engine tipping forward and pulling on a dodgy electrical connection which wouldn't happen if it tipped backward. this should be fairly easy to spot as you would have some pretty tight cables.

Try increasing the idle speed, as it might be running on the anti stall device as the idle bolt/screw can come lose or even fall out. Wait for the car to warm up before adjusting the idle speed turn the idle up to 1500rpm ish (if you still have the screw in the back of the throttle body) then adjust it back down to 950 to 1000 rpm and don't forget to blip the throttle once you have adjusted the idle either way.

Hi all,

Just thought I would do an update of this post as I am still experiencing the problem.

I unplugged the brake booster vacuum hose and sealed the hole to the engine. Test drove and till have the problem. I also tried braking with the hand brake - still the same issue. So Im pretty sure I can cross the brake booster as being the problem off my list.

I've also checked the fuel pump relay, and that is fine.

I've also made a quick video of the problem.

Golf stalling issue - YouTube

The next step is to take a look at the IAC valve.

Any help is still very much appreciated!

If it still happens when you brake with the hand brake, I think you can rule out the main braking systems vacuum tubes/servo etc.

I cannot think of any logical reason for this happening.
The lack of answers to your post says a lot too - You have stumped all the techy boffins!

If you get the car moving, put the car into neutral, lift the revs with your right foot and brake with your left foot, does it still stall?

I think this has to be electrical, though I can't think of any obvious things to check!
The fact it only happens in forward gears and not in reverse is extremely puzzling.
Does it happen when going backwards but with the box knocked into neutral before applying the brakes?

When the engine cuts out do all the lights on the dash also go out ??? In other words do you lose power ??? 

Try checking the earths I had this problem with one of my old golfs 

Maf sensor can cause to cut out as well if it has one 

i would say an earth or short somewhere along the ignition line, have you done a fuel pressure test whilst holding the brake on?
it can only be 3 things;
spark, fuel, air!

ill have a further thing and see if i can come up with something else!

Didn't some of some  the old alarm systems use an immobiliser connected to the brake pedal somehow ?    …thinking you had to press the pedal before the engine would fire up …
a long shot but might be interested worth  doing a search on Google ? 

mk1jim said

Didn't some of some  the old alarm systems use an immobiliser connected to the brake pedal
somehow ?    …thinking you had to press the pedal before the engine would fire up
…
a long shot but might be interested worth  doing a search on Google ? 

I had one like that when I had a mark 2 

But would the car not still stall when in reverse if it had a electrical device/alarm fitted to the brake pedal as the car only stalls when going forward???????
This is really a stange problem and one I've never seen/heard of before…….

Well I admit that I shot myself in the foot when I said we could solve this, I'm sorry mate!    

But I have one Ace up my sleeve, a guy called John, no disrespect to other members but if he can't fathom this out no one will.
It's rumoured that when he was born his Parents used to liquidise Golf MK1/2 workshop manuals and bottle feed him!     

So rubjonny , John can you get your head round this Sir?     

LennyD said

When the engine cuts out do all the lights on the dash also go out ??? In other words do you lose power ???

Havent tried it with the headlights on but there appears to be no loss of electricity - gauges and radio remain on. I can start it straight back up again too.

golfcabrio said

Well I admit that I shot myself in the foot when I said we could solve this, I'm sorry mate!    

But I have one Ace up my sleeve, a guy called John, no disrespect to other members but if he can't fathom this out no one will.
It's rumoured that when he was born his Parents used to liquidise Golf MK1/2 workshop manuals and bottle feed him!     

So rubjonny , John can you get your head round this Sir?     

No problem!    thanks for all the suggestions! I'm officially well passed the limits of my knowledge and so have book her into a local VW mechanic.

Ill be sure to post whatever he finds here!

very bizarre problem, did you check the lifter pump is all ok, plus the fuel reservoir under the car near the filler neck?

also, listen carefully to the sound the fuel pump(s) make just as the car cuts out. do they carry on runnign for a few seconds after the cut, and do they get louder just before? listen carefully for any clicks from the fusebox area as well.

the cut out looks quite gradual, and it does seem like the revs are 'caught' just before they fully cutout but whatever is doing the catchign cannot compensate and so revs fully die. there may be a idle speed valve on the driver side turret, but with it being so late it might be a bit different since it'll probably be using some kind of CIS-E system rather than the basic stuff you normally see here.

I'm not sure exactly which system you have, but have a look thru this link at the CIS-E stuff see if anything matches up:
http://vnc.thewpp.ca/stuff/bentley/ep0niks.ctech.ca/vw/eva2/FU01/index.html

Hi all,

Well the VW mechanic has (probably) found the issue:

There is a rubber o-ring or grommet on the fuel transfer pump assembly that has disintegrated (probably becuase the last owner left a good amount of fuel in the tank whilst it was in storage) and as the car slowed and the fuel sloshed around this was exposed letting air into the fuel lines.

Unfortunately he thinks this has broken the pump as well, so I am sourcing a replacement pump.

I say 'probably' as theres no way of telling this is the problem until we replace and test.

Thanks for all the help and suggestions! Will let you know how it turns out!