Cutting out while driving.

ZRZ

Active Member
Dec 30, 2014
284
0
Hertfordshire
Hey all,

Recent issue, has happened twice now! Car has randomly cut off while driving, losing power steering etc.

Doesn't restart form just turning the key, it fires for about a second and then dies again. Will restart when holding foot on accelerator while turning key but then sits at around 1200RPM as if the choke has kicked in?

What can cause this sort of issue? Is happened the first time about a week ago, no issues until tonight when it happened again. Hopefully nothing too costly!


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mty12345

Active Member
Jun 17, 2011
3,727
451
bristol
Bit of a random one mate. not heard of similar before. Are there any fault codes stored? Have you checked battery connection is ok?
 

ZRZ

Active Member
Dec 30, 2014
284
0
Hertfordshire
Battery is brand new and all in tact, terminals are all on properly.

No unusual fault codes that I wasn't already aware of!


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mty12345

Active Member
Jun 17, 2011
3,727
451
bristol
Are all the electrics still on when it happens? If so then i'd guess it's not getting enough fuel for some reason :think: maybe the fuel pump or the fuel pump relay intermittantly failing??

Have you changed fuel filter recently? If not then maybe worth doing that too.
 

RichyH

Active Member
Dec 20, 2015
290
7
Lincoln, UK
Dirty throttle body? Dirty MAF could be issues. Both DIY jobs. Maybe a fuel issue, try a new fuel filter if the two above don't work and/or super unleaded for a while


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ZRZ

Active Member
Dec 30, 2014
284
0
Hertfordshire
Electrics were still working so rules out alternator!

MAF was cleaned about a month ago so shouldn't be that.

Will have the try TB clean and change the fuel filter. Would either cause it to be so intermittent I.e nearly a week apart!

I'll have a look at hose Chris, thanks!


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ChrisGTL

'Awesome' LCR225
Nov 17, 2007
2,459
2
Huddersfield
Electrics were still working so rules out alternator!

MAF was cleaned about a month ago so shouldn't be that.

Will have the try TB clean and change the fuel filter. Would either cause it to be so intermittent I.e nearly a week apart!

I'll have a look at hose Chris, thanks!


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Any pattern to your problem? Does it only do it when engine is up to temperature or does it do it completely random?

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ZRZ

Active Member
Dec 30, 2014
284
0
Hertfordshire
Both times engine has been up to temperature, both times it's happened when revs are low or clutch has been pressed. Both times at a very low speeds of 5-10mph


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ChrisGTL

'Awesome' LCR225
Nov 17, 2007
2,459
2
Huddersfield
Both times engine has been up to temperature, both times it's happened when revs are low or clutch has been pressed. Both times at a very low speeds of 5-10mph


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Why did you clean the MAF out of interest? Did you feel like the MAF was dying so you cleaned it? What did you clean it with? Isopropanol Alcohol?

My thinking is a split hose or sensor problem. Also have a look under the manifold for split vac hoses.

Are you running the Forge DV?



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ZRZ

Active Member
Dec 30, 2014
284
0
Hertfordshire
Had some issues with the car going into limp mode so cleaned the MAF although it looking pretty new anyway. Was cleaning with contact cleaner.

Yeah running a forge recirc


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ChrisGTL

'Awesome' LCR225
Nov 17, 2007
2,459
2
Huddersfield
Had some issues with the car going into limp mode so cleaned the MAF although it looking pretty new anyway. Was cleaning with contact cleaner.

Yeah running a forge recirc


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Was the MAF the reason for limp mode? My experience is that MAF's often look in good condition even though they are failing.

I guess you could unplug the MAF next time you have a stalling issue and see if it helps. If your engine runs better without the MAF plugged in I would suggest replacing with a genuine OEM part.

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ZRZ

Active Member
Dec 30, 2014
284
0
Hertfordshire
Limp mode is caused by something to do with the EPC that still hasn't cured itself but is also an intermittent issue.

Next time it happens I'll try unplugging the MAF and see if it restarts without touching the accelerator.


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ZRZ

Active Member
Dec 30, 2014
284
0
Hertfordshire
Throttle Body has been checked and apart from a very small amount of grainy dirt it was very clean. Gave it an extra clean but doubt that will have been the culprit.

So, no EML code to the issue, battery light illuminating and requiring some accelerator depression to start are the symptoms.

Possibly fuelling issue? If so where to start?


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mty12345

Active Member
Jun 17, 2011
3,727
451
bristol
Limp mode is caused by something to do with the EPC that still hasn't cured itself but is also an intermittent issue.


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IMO that will 99% be the cause of the issues, definitely the not responding to the pedal when you restart it syptoms...... I'm pretty sure i remember reading in ELSAWIN somewhere that when the ecu can't determine the throttle position from the EPC, then it defaults to "fast idle" at 1200rpm so it's possible to drive home etc.

The stalling may be unrelated, but you need to sort the EPC issue first as it may just be cutting out because it doesn't know where the throttle plate should be.

You say you cleaned the TB. did you do the realignment with VCDS/vagcom?

Can you post up ALL the fault codes you have especially the EPC ones.

If the maf is working properly then you should see between 2g/s and 4.5g/s at idle on the AUQ engine. In my experience they are usually pretty reliable unless you are running an oil covered airfilter, in which case they tend to get covered with the oil and die pretty quickly.
 
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ZRZ

Active Member
Dec 30, 2014
284
0
Hertfordshire
These are the fault codes I got from a simple code read:

EDIT: Car is decatted

39c1dd398d67e04537db2fb4134cfc35.jpg



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mty12345

Active Member
Jun 17, 2011
3,727
451
bristol
I think you need to get it on VCDS mate. Both to realign the TB after you cleaned it and to get more idea of what that EPC code is. The VCDS code should be a lot more specific than on torque or any other OBD2 reader.

I'm guessing that with the front O2 sensor heater not working that it's permanantly running in open-loop mode? You can check that on torque by adding a new display and selecting the "fuel status" gauge from the list. It should say "closed-loop" when up to temp.

If it's in open rather than closed, then it's effectively guessing at the fuel mixture needed rather than using the O2 sensors. Combine that with the fact it's not sure where you foot is on the accelerator, then i can understand it misjuding the fuel enough for it to just stall when the revs are close to idle.

I'd get both the O2 sensor and the EPC fault sorted first if i was you mate, otherwise i think you'll just be constantly chasing your tail so to speak.


EDIT: Just looked here and seems that O2 sensors and EPC share a common connection inside the ECU and can cause all sorts of issues. http://forums.vwvortex.com/showthre...-code-p2138-EPC-Problem-PLEASE-LOOK-NEED-HELP
 
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ZRZ

Active Member
Dec 30, 2014
284
0
Hertfordshire
Nobody local to do a VCDS check is the issue to be fair. Might have to chuck it over to SEAT to have a look at the codes.

Is the 02 code not caused by the decat then by the looks of things?


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mty12345

Active Member
Jun 17, 2011
3,727
451
bristol
No, P0030 and P0135 are both for a fault with the front O2 sensor, which is the one before the cat. That sensor is responsable for the fueling mixture of the engine..... It's quite possible that the wiring to it was damaged when the cat was removed. That would be the first thing i would check before you go to the dealer.

Chances are if you can find the problem on that, than the EPC code might be sorted too, judging by the thread i linked you too above.

I would disconnect the battery before you start looking, just to be safe, as i've heard cases of the O2 sensors shorting out and frying the ECU at the same time.

The P0420 code,cat below threshold is related to the decat though and nothing to worry about as such.
 
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Maria

my mid-life crisis car
Jun 22, 2016
143
20
South-West
Sounds to me more like fuel starvation ie bunged up filter, dirty injector or something, rather than a leaking hose.
If it was a leaking hose you'd expect it to happen reliably and progressively worse when booting it eg pulling away.
 
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