Cutting out helllllp

So…… when I hammer the break my mk1 gti 1985 1.8 cuts out and I can’t for the life of me work out why I will list everything I have changed/ ruled out see if any of you wonderful people have any ideas

From the back
In tank pump
Under body pump
Fuel lines all the way to the fuel filter
Fuel filter
Ignition module
Fuel distributor (whole top of the air box)
Warm up regulated
Fuel pump relay
Cleaned the earths under the glove box (crown connection)

I think that’s it

Any help would be great


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Also runs really lumpy when left out in the sun all day not sure if related


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Are you saying it cuts out when you brake hard? Sorry it's a bit difficult to understand the question (maybe my age lol). Anyway if that's the case, have you got any hissing noises coming from your pedal area? Thinking vacuum leak from servo.

Yes it runs and drives fine if you are gentle but any hard braking and it stalls, then it’s just turn key on and off again and it’s fine, I have changed the vacuum pipe on the part connected to the air box


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Find yourself a deserted road. Disconnect your vacuum hose from servo and block it off. Your brakes will be hard, hence the deserted road. See if it still cuts out.

Ok great thanks I?ll try that tomorrow ?


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This hose, disconnect and block hose off with some sort of plug.

Should i bloke the hose or the connector on the servo


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The hose it's self. Does it cut out idling if you press the brakes hard?

Ok cool I’ll try that no it doesn’t if sitting still


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May not be the problem, give it a try anyway.

Thinking about it it can’t be the brake servo vacuum because when I pull the hand brake up hard it also stalls out, I am well and truly stumped


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Forget the brakes for a minute. If it's only happening under hard deceleration then maybe something is being moved. Have you checked there's nothing loose on your wiring. Bad connectors etc. I wouldn't of thought it was a fuel issue, but it could be. Is your clutch fully disengaging?

Yer it feels as if something is rocking as I slow down and breaking a connection or suffocating the engine, I have looked around for something loose but can’t see anything,the engine and everything on it all seems to be very sturdy when dropping the anchor

If the clutch wasn’t disengaged wouldn’t it slip and smell bad (it doesn’t)


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No it would be the opposite. You would have  a low biting point and it may crunch when putting it into gear.

Put it in neutral then brake hard, does it cut out?

No it’s only when moving or stopping fast


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What is the idle speed?

Get the engine warm and try increasing the idle speed via the screw on the throttle body to 1200 rpm, blip the throttle a couple of times and then lower it to 1000 rpm.

I could be the idle screw is working it's self lose and the car is ticking over on the anti stall device, the sudden stopping could be the device is not kicking in quick enough to stop it stalling.

Its a simple thing to try and is free   

It idles at 1000rpm quite well, although when I blip the throttle sometimes it drops a little below 1k and comes back up would that be expected if the screw was loosening is this the screw I should be checking this is a spare throttle body I have


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No that's not the idle screw..

Its here.  I think you need a 7mm spanner.
http://www.mk1maintenance.com/adjusting-the-idle-on-a-1.8lt-injected-engine.html