VAG codes - Help Please ( bit long winded , sorry )

2004 A3 2.0 fsi sport.

While driving the other day my car lost power and became unresponsive to throttle input ( travelling at 70mph in 6th gear ) I put my foot on the clutch and pressed down on the throttle and the engine revved freely, took my foot off the clutch and still no power. The power returned after a few seconds and was driving normally until it happened again when I was just at the top of a hill and took my foot off the throttle.
When driving in town it has also started to lose & regain power, usually on a slight upward slope and when I have just changed gear from 1st to 2nd or from 2nd to 3rd. Has also lost power when on the flat in 3rd, 4th & 5th gear, usualy for a couple of seconds then power on for a second then no power again then it comes back and is fine.( has happened at various speeds between 20mph - 70mph )

Pulled the codes and came up with.

16825 - evap emission control
16575 - fuel pressure sensor - plausible signal error
18974 - low fuel pressure
17480 - nox sensor

Had the following done..
Pressure tested fuel rail
Cleaned rail pressure valve & sensor
Stripped & cleaned throttle body & TPS
Replaced fuel filter.
Checked all connections & hoses ( none loose and no cracked hoses )

Took it for a spin and the problem still exists but is now more frequent.

Pulled codes again and only got.. 16575 - fuel pressure sensor - plausible signal error

Power loss seems to only happen when engine is warm.
Seems to happen only when you have eased your foot off the throttle and reapplied it.

MIL has not come on before, during or after any power loss event.

Probably coincidence ? but I have had 3 bulbs blown in the past week.

Now thinking of replacing fuel pressure sensor but not sure if that will achieve anything ?

Any ideas ?


Thanks

Haven't got round to rescanning, last scan was this morning and only 16575 appeared. Have cleared that and waiting for the fault to appear again. Will probably rescan on Friday.

Previous scans have all had , 16825, 16575, 18974.
The second last one also had 17480

The fault occurs regardless of how much fuel is in the tank.
I have noticed that the idle speed is fluctuating when sitting in neutral, falls down to 650 rpm then back to just under 800 rpm.

Intrestingly this problem only started to happen after I switched to using Shell V Power a month ago. Wonder if that could be upsetting some sensor or other ?

Toying with the idea of putting in RON95 to see if that cures it. lol. But I know the emission sensors wont like that and the MIL will come on.

FUNKYCLIFF said:

The 2.0 fsi sport has been known to have issues with the Crank angle sensor,the crankshaft sensor and the coolant temperature sensor, i replaced these when i had my cambelt done and i dont get anymore error messages or idling problems but maybe i just got lucky :thumbsup:.

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When is the cambelt due ( is it 60,000 miles ? I've got 51,000 on the clock at the moment )
Replaced coolant temp sensor months ago after the MIL coming on and the cooling fan running constantly.
Crankshaft inspected earlier this month and found to be ok. No codes related to crankshaft being thrown up.

Khufu said:

I've used Shell V in mine with no problems. Using Ron95 wont cause any problems with the MIL light etc, it will just ****** the timing slightly meaning slightly less power/mpg but you wouldn't really notice it.

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Noticably less power / mpg And kept having activated charcoal filter codes coming up with the MIL on when running on RON95 along with the temp problem above.

NHN said:

I would change the sensor then go from there as obviously if its not reading correctly it will have fairly adverse effects on the car.

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That was my thought, but what are the chances of the sensor being fine and the ECU being faulty ?

Originally thought it might be the ESP kicking in and the ECU cutting the power but the ESP checks out ok with no relavant codes recorded ( or ESP light on dash when driving )

New sensor ordered and hopefully fitted by the weekend.

Thanks for all the comments everyone.