2004 Golf 4 GTI (AGU)- Missing on full throttle

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8VALVE-zn
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2004 Golf 4 GTI (AGU)- Missing on full throttle

Post by 8VALVE-zn » Thu Jun 14, 2018 3:38 pm

Hi guys,

So a friend of mine at the workplace has a Golf 4 GTI that is currently doing a tad over 300,000km's. The engine has never been opened before, and I must say that for its age the car goes really well.

So onto the problem:

When idling: The car has a clear miss below 3000rpm, over that and it sounds clean.

When driving: The car has an even bigger miss once load is applied, the miss is more apparent at WOT than POT. However, what is very strange is that the problem is there most of the time but clears out every now and then- in this case the car goes perfectly fine like it should. In 2nd gear @ POT, the car would surge from idle to about 3500rpm and if kept at POT- @ 4000rpm the miss would clear out and the car would go perfectly.

Things that have been changed: O2 sensor, N75 valve

What are the other possible things that could be looked at?

Good help is always appreciated.
2000 Golf 1 Chico- CRANKCASE [Std bottom end, head gas flowed,ported & chopped by Fastcar, 288 Estas Billet, 4-2-1 43mm Brospeed Branch, 50mm-57mm-63mm Exhaust] + THE PART (2B1 speacials) -Final power @ Autotrix 111wkw & 210wnm :drool:

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Re: 2004 Golf 4 GTI (AGU)- Missing on full throttle

Post by farrell15 » Thu Jun 14, 2018 3:51 pm

8VALVE-zn wrote:Hi guys,

So a friend of mine at the workplace has a Golf 4 GTI that is currently doing a tad over 300,000km's. The engine has never been opened before, and I must say that for its age the car goes really well.

So onto the problem:

When idling: The car has a clear miss below 3000rpm, over that and it sounds clean.

When driving: The car has an even bigger miss once load is applied, the miss is more apparent at WOT than POT. However, what is very strange is that the problem is there most of the time but clears out every now and then- in this case the car goes perfectly fine like it should. In 2nd gear @ POT, the car would surge from idle to about 3500rpm and if kept at POT- @ 4000rpm the miss would clear out and the car would go perfectly.

Things that have been changed: O2 sensor, N75 valve

What are the other possible things that could be looked at?

Good help is always appreciated.
Does he or yourself have access to VCDS?

Sounds like maybe plugs could be gapped wrong or even a failing coil pack but I can't say for sure. If you have access to a scanner scan it for errors it's usually a good to start.

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Re: 2004 Golf 4 GTI (AGU)- Missing on full throttle

Post by farrell15 » Thu Jun 14, 2018 3:51 pm

8VALVE-zn wrote:Hi guys,

So a friend of mine at the workplace has a Golf 4 GTI that is currently doing a tad over 300,000km's. The engine has never been opened before, and I must say that for its age the car goes really well.

So onto the problem:

When idling: The car has a clear miss below 3000rpm, over that and it sounds clean.

When driving: The car has an even bigger miss once load is applied, the miss is more apparent at WOT than POT. However, what is very strange is that the problem is there most of the time but clears out every now and then- in this case the car goes perfectly fine like it should. In 2nd gear @ POT, the car would surge from idle to about 3500rpm and if kept at POT- @ 4000rpm the miss would clear out and the car would go perfectly.

Things that have been changed: O2 sensor, N75 valve

What are the other possible things that could be looked at?

Good help is always appreciated.
Does he or yourself have access to VCDS?

Sounds like maybe plugs could be gapped wrong or even a failing coil pack but I can't say for sure. If you have access to a scanner scan it for errors it's usually a good to start.

Sent from my SM-N900 using Tapatalk

2009 Hyundai Tiburon FL2 GTv6 (Big turbo project)
2009 Golf MK5 GTI dsg (SOLD)
1979 Golf MK1 2L (SOLD)
2007 Polo 1.9 TDI (BEEEEEEG turbo) (SOLD)
1998 Jetta MK3 ABF 2.0 16v (SOLD)
1990 Jetta MK2 ABF
1968 Baja bug 2.0 Kombi project ABF (SOLD)

Precision Auto Works

2003 Audi 1.8t 20v GT28
2002 Polo 9n 1.9 tdi PD100

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8VALVE-zn
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Re: 2004 Golf 4 GTI (AGU)- Missing on full throttle

Post by 8VALVE-zn » Thu Jun 14, 2018 4:13 pm

Testing of the coilpacks will happen today.

The missing story is very very irritating because it could be anything really

Thanks for that!
2000 Golf 1 Chico- CRANKCASE [Std bottom end, head gas flowed,ported & chopped by Fastcar, 288 Estas Billet, 4-2-1 43mm Brospeed Branch, 50mm-57mm-63mm Exhaust] + THE PART (2B1 speacials) -Final power @ Autotrix 111wkw & 210wnm :drool:

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Re: 2004 Golf 4 GTI (AGU)- Missing on full throttle

Post by DCmk3 » Thu Jun 14, 2018 4:20 pm

AGU coilpacks are pretty robust and don't often fail like the other 20v turbo engines coils.
Any idea if there is software on the car?
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Re: 2004 Golf 4 GTI (AGU)- Missing on full throttle

Post by 8VALVE-zn » Fri Jun 15, 2018 8:18 am

The car is completely stock.

What's baffling is that the problem is only there every now and then.

The coilpacks have still not being tested, the coilpacks have been changed over the life of the vehicle (remember its on 300k km +).

There is a bit of a fuel smell coming into the car ever since the problem started.

Today it seems like the issue of missing is there even at POT, strangely tho if kept at POT and the engine is allowed to revv up past 4000rpm the issue some what clears up.

What else can be checked at this point?
2000 Golf 1 Chico- CRANKCASE [Std bottom end, head gas flowed,ported & chopped by Fastcar, 288 Estas Billet, 4-2-1 43mm Brospeed Branch, 50mm-57mm-63mm Exhaust] + THE PART (2B1 speacials) -Final power @ Autotrix 111wkw & 210wnm :drool:

2011 Jetta 5 1.6 TDI DSG - CRANKCASE Tow Services [CPI Stage 1 with DPF Delete]
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Re: 2004 Golf 4 GTI (AGU)- Missing on full throttle

Post by DCmk3 » Fri Jun 15, 2018 9:11 am

Fuel or vacuum leak perhaps, check the injectors cups which are screwed into the intake manifold and see if they are leaking as you will easily spot if there's a leak. The injectors basically get seated in them.

Those parts fail over time I've had to replace mine as well.
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Re: 2004 Golf 4 GTI (AGU)- Missing on full throttle

Post by panic-mechanic » Fri Jun 15, 2018 10:55 am

Check the air/fuel ration on a dyno. If the thing goes lean under boost it will missfire as well. had quite few of them recently - the pumps are now at that age that they are starting to fail. The fact that it does it on WOT mostly can definitly point to a lean situation.
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Re: 2004 Golf 4 GTI (AGU)- Missing on full throttle

Post by 8VALVE-zn » Mon Jun 18, 2018 12:58 pm

what are the apparent problems experienced with a bad N75 valve? And what are the symptoms of a bad N75?
2000 Golf 1 Chico- CRANKCASE [Std bottom end, head gas flowed,ported & chopped by Fastcar, 288 Estas Billet, 4-2-1 43mm Brospeed Branch, 50mm-57mm-63mm Exhaust] + THE PART (2B1 speacials) -Final power @ Autotrix 111wkw & 210wnm :drool:

2011 Jetta 5 1.6 TDI DSG - CRANKCASE Tow Services [CPI Stage 1 with DPF Delete]
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Re: 2004 Golf 4 GTI (AGU)- Missing on full throttle

Post by DCmk3 » Mon Jun 18, 2018 2:21 pm

A failed n75 would generally result in overboosting as it doesn't handle the boost pressure appropriately or it could result in no boost if it's somehow stuck open.
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Re: 2004 Golf 4 GTI (AGU)- Missing on full throttle

Post by panic-mechanic » Mon Jun 18, 2018 6:56 pm

n75 stuck open will cause overboost. Stuck closed or have died will cause underboost or basically just wategate pressure which is 0.3 bar.
Closed is it's default valve - held there with a spring. activating the circuit opens the valve
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Re: 2004 Golf 4 GTI (AGU)- Missing on full throttle

Post by DCmk3 » Mon Jun 18, 2018 7:48 pm

Oh right, mixed those up.. :twisted:
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Re: 2004 Golf 4 GTI (AGU)- Missing on full throttle

Post by 22irwin.mercure » Sat Jun 23, 2018 9:26 am

Check if your fuel pump was replaced bud .

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Re: 2004 Golf 4 GTI (AGU)- Missing on full throttle

Post by madhoshival » Sun Jun 24, 2018 2:40 am

Is the misfire only there on boost? Did you check for boost leaks? Also check your map sensor.


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