6n2 polo cuts out when driving

[Finleye2000]

Hi there, I have a 1.0mpi 6n2 as my first car. Just passed it’s MOT with 0 problems and has started having a problem with the engine cutting out and sometimes not starting.
The engine only occasionally cuts out when accelerating and loses all power steering and brakes along with it. Nothing on the dash is lit up other than the battery icon.
Once it does this it can start first time or sometimes take 3/4 tries before it fires and runs properly.
At other times it will continually crank for 10/15 seconds before anything happens at all.
The fuel pump does not prime every time I turn the key.
Scanned the ecu with my OBD11 device and also with VCDS but no faults appeared at all.

I’m going to try a new fuel filter as I can’t see it’s been changed at all in the service history, just hoping I can get it sorted as am planning to sell it next month.
Any help or suggestions will be greatly appreciated

[Hamza mostafa]

I would say it’s either the fuel filter or fuel pump, sounds like it doesn’t deliver the necessary amount of fuel to keep the car running while driving and sometimes upon startup. Also you did mention that the fuel pump sometimes does not prime before starting which leads me to think that it is the fuel pump that has gone, hope this helps


Sent from my iPhone using Tapatalk

[Finleye2000]

Thanks for the reply, I’ll see how I get on with the fuel filter first and then move onto the pump if it doesn’t improve as it’s an expensive replacement.
Yeah that’s right I’ve not heard it prime every time but I did read on another thread that the 6n2 doesn’t prime every time anyways.
Could it be water in the tank? I did jet wash my car the about a week ago so water could’ve got in the tank. Not sure what the symptoms of water in fuel are though

[937carrera]

I think that's an electrical problem, rather than fuel. Alternator light is a clue, the steering and brakes are a bit perplexing

Try the easy stuff first:

Connections onto the battery, alternator connections, engine earths, main fuses on top of the battery (I'm assuming it's the same as a GTi

Can you get a multimeter and see what the voltage across the battery is when the engine is idling ?

Also make sure all the intake hoses are secure and not leaking, especially onto the throttle body

[Finleye2000]

Just did a little multimeter test:
12.5v non running
13.5v running 800rpm
14.1v at 1500/2000 rpm
My knowledge with multimeters is limited so I don’t know how to test ground wires
I can hear some sort of suction noise as you sharply rev the engine while stationary with the bonnet open, but I have no idea wether it sounded like that before.
I’ve removed the rear seat and pump inspection cover so I can hear the pump more clearly, but haven’t had it stall on me again yet.
Next thing to do it replace the filter when I get it tomorrow and have a closer look at wether the intake should be making that suction sound.

[937carrera]

Alternator readings are as I would expect, so that's working fine.

My idea(s) are, either there's a bad electrical connection which makes / breaks as then engine moves back under accelleration. Put the meter onto resistance / ohms and make sure there is good continuity (zero ohms) along the earth connections and the main fuses on top of the battery. Check these in particular as they can get micro cracks which cause problems.

My second idea is that movement of the engine is allowing an air leak on the intake which messes up the fuelling information for the ECU. The suction noise is pointing towards that, nice & easy check to make sure that all the connections are on properly and secure

[Finleye2000]

I think it’s safe to say it’s nothing to do with fuelling. Replaced the filter this evening and fuel ran through it just fine,although there were some black gritty deposits flowing out the back.
Ive now discovered that when the engine is idling, if you slightly but sharply stab the throttle, you hear the engine suck in a load of air and the revs drop to about 3/400 but no stall. I guess when under load accelerating this is why it will sometimes stall. However if you gradually increase the throttle, engine runs sweet.
There is a slight noticeable hissing while engine is running and also for a short while after the engine is turned off. But cannot he heard when doors and bonnet is closed.

Any places that fail on the intake manifold in particular? I removed the cover and made sure all the hoses were connected properly but still making the sounds.

[937carrera]

I don't have the 1.0l engine so can't give you too much specific advice, sorry.

There's a decent chance that now the likely problem has been identified you can solve it, just have to find out where the leak is.

Other forum members, & especially Alex, can hopefully point you in the right direction. Keep posting

[alexperkins]

I had a 1.0 6N2 many years ago

This sounds like a typical faulty ignition switch

Hissing might be a split in the servo hose from the TB to the brake servo as these often split

[937carrera]

Thanks Alex

Ah, the welcome voice of experience

Looks like you have two potential faults. I would access the ignition switch and wiggle the connections while the engine is running to see if it cuts out

[Finleye2000]

Sorry for late reply guys, I’m middle of sorting a few cars out.
Ok thanks for the info, I’ll give that a try. I guess the switch is in the ignition barrel bit somewhere? I have had all the locks fail on me now so wouldn’t be surprised if it’s that

[Finleye2000]

Finally got round to having a proper look at this problem. Ended up being that the plastic brake servo hose had completely split and was obvious when I had the cover off and engine running. New hose was £35 from local garage and should be back running sweet again soon.
I had been driving it for a few miles when I noticed I had very little assistance with braking, (pedal suddenly became hard to press after it had stalled) so should’ve known it was that all along!!

[alexperkins]

Super stuff

Was the ignition switch faulty also? As the brake servo hose won’t stop it starting or the fuel pump priming

[Finleye2000]

Not sure, it’s definitely stopped hissing. I’ll drive it a bit tomorrow and see if it will stall. The ignition barrel is noticeably worn after using my golf. Doesn’t really click into each one, just feels really loose. Are they a pain to replace? I’m meant to have someone coming to look at it to buy on Sunday.
Also having it sat in gear for a couple weeks has caused the clutch biting point to be on the floor, but I’m hoping a quick adjustment of the cable will sort this. Still gets into all gears including reverse fine.

[Finleye2000]

Ok so we got a few more stalls and trouble starting annoyingly. When I turn the key in the ignition it will crank the engine and attempt to start but cutout straight away. Would a faulty switch still allow the engine to crank over?? There’s no immobiliser (I don’t think) so it can’t be a problem with that.