Author Topic: Hard starting/ rough idle when warm  (Read 1179 times)

Offline Q451m

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Hard starting/ rough idle when warm
« on: 01 June 2020, 19:03 »
Hi All,

Thank you for accepting me to the forum, I have owned my 09 mk6 GTI since 2018. Abit of a back story, March 2020 the timing chain snapped on my car, the resolution was to purchase a rebuilt engine and fit. Since then I have barely driven the car due to the Covid-19 lockdown. However now I have started driving the car it has developed a fault with the car idling rough when hot and sometimes stalling when stopped and also hard starting when starting it 10/15 minutes after it has been driven. We have tried changing the coil packs however the issue persists. A scan using vagcom only shows p0172 system too rich bank 1.

Sorry if this has already been logged by someone else if so please point me in the right direction. If not I’d really appreciate your advise. Thanks in advance

Offline Snoopy

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Re: Hard starting/ rough idle when warm
« Reply #1 on: 02 June 2020, 15:51 »
Possible Causes

    Fuel system
    Excessive fuel pressure
    Leaking or contaminated fuel injectors
    Leaking fuel pressure regulator
    Low fuel pressure or running out of fuel
    Vapor recovery system
    Air leaks after the MAF
    Vacuum leaks
    Improper seated engine oil dipstick
    Stuck EGR valve
    Oil overfill
    Cam timing
    Cylinder compression
    Exhaust leaks before or near HO2Ss.


If I had to guess from the most common I would say fuel injector sticking open.
Current Stable: Mk6 GTI, Mk1 GTI, Mk1 Leon & 3 non VW.

Offline Q451m

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Re: Hard starting/ rough idle when warm
« Reply #2 on: 11 June 2020, 12:28 »
Thanks for the reply Snoopy, I’ve checked the fuel rail pressure on vagcom and that is well within the threshold, tried a new set of injectors, coil packs sparks, and the cam timing also changed the tensioner to be on the safe side. Will look at the other suggestions below too

Offline Q451m

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Re: Hard starting/ rough idle when warm
« Reply #3 on: 21 June 2020, 13:55 »
Hi All just a quick update, the issue is very intermittent. You think you’ve fixed it and then it comes right back at you, drove the car for 20 miles today and all was good, got to the end of the drive and it started to misfire again.

I have had a mechanic complete a compression test and the compression on all 4 cylinders is fine. I am currently trying to find someone in West Yorkshire who would be able to do a smoke test to look for leaks.

Are you also able to advice how the vapour system and low pressure fuel pump can be tested?

Offline weejockvw

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Re: Hard starting/ rough idle when warm
« Reply #4 on: 21 June 2020, 16:10 »
Can’t it be something as simple as a spark plug

Offline Q451m

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Re: Hard starting/ rough idle when warm
« Reply #5 on: 21 June 2020, 18:04 »
It maybe, it’s very intermittent I plugged it in to the vagcom and got approx 50 misfires from cylinder 2 swapped coils around and that dropped down to 20 odd, I have ordered some coil packs from awesomegti and will change the spark plugs too

Offline Snoopy

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Re: Hard starting/ rough idle when warm
« Reply #6 on: 22 June 2020, 06:24 »
Hi All,

Thank you for accepting me to the forum, I have owned my 09 mk6 GTI since 2018. Abit of a back story, March 2020 the timing chain snapped on my car, the resolution was to purchase a rebuilt engine and fit. Since then I have barely driven the car due to the Covid-19 lockdown. However now I have started driving the car it has developed a fault with the car idling rough when hot and sometimes stalling when stopped and also hard starting when starting it 10/15 minutes after it has been driven. We have tried changing the coil packs however the issue persists. A scan using vagcom only shows p0172 system too rich bank 1.

Sorry if this has already been logged by someone else if so please point me in the right direction. If not I’d really appreciate your advise. Thanks in advance
I thought you had already changed the coil packs?
Current Stable: Mk6 GTI, Mk1 GTI, Mk1 Leon & 3 non VW.

Offline Q451m

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Re: Hard starting/ rough idle when warm
« Reply #7 on: 22 June 2020, 10:52 »
Hi, yes they were changed, however the ones used were from euro car parts so I was advised to change them again and get better quality ones

Hi All,

Thank you for accepting me to the forum, I have owned my 09 mk6 GTI since 2018. Abit of a back story, March 2020 the timing chain snapped on my car, the resolution was to purchase a rebuilt engine and fit. Since then I have barely driven the car due to the Covid-19 lockdown. However now I have started driving the car it has developed a fault with the car idling rough when hot and sometimes stalling when stopped and also hard starting when starting it 10/15 minutes after it has been driven. We have tried changing the coil packs however the issue persists. A scan using vagcom only shows p0172 system too rich bank 1.

Sorry if this has already been logged by someone else if so please point me in the right direction. If not I’d really appreciate your advise. Thanks in advance
I thought you had already changed the coil packs?

Offline Q451m

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Re: Hard starting/ rough idle when warm
« Reply #8 on: 25 June 2020, 14:35 »
Hi,

Quick update, I have changed the coil packs to the r8 style and that has solved the misfiring issue, however the car is still showing p0172 and occasionally idles abit rough. I have two questions,

Will I need to reset the fuel trim adaptations for it to adapt.
And secondly is anyone aware of a reputable garage I can take it to near West Yorkshire to investigate, a lot of indies seem to be fobbing it off because the fault is not pointing towards an exact fault and I don’t want to visit the stealers 😫

Offline Snoopy

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Re: Hard starting/ rough idle when warm
« Reply #9 on: 25 June 2020, 16:54 »
The ruff idle to rule somethings out as just have a feeling.

What miles are on the replacement engine. There maybe excess carbon on the valves causing the misfire. Have you had it compression tested?

Do you have an oil leak between the gearbox and engine. Look under front of car and see if oily between gearbox and engine. Increased crankcase pressure that result in rear main fail can cause idle issues too.

If you ask on the main forum someone should be able to point you to a specialist in your area.
« Last Edit: 25 June 2020, 22:28 by Snoopy »
Current Stable: Mk6 GTI, Mk1 GTI, Mk1 Leon & 3 non VW.