Erratic throttle response when cold

[HPsauce]

Originally Posted by Delboy

is it possible to log the pots in VCDS and go for drive, then once you have a fault scenario you can timestamp I vcds so the log shows when the fault was so you may find it easier lookng through the log later.

I'm beginning to think I'll have to do that, but it will probably take whole a load of test runs to get anything useful.

I added more info earlier after taking the knee panel off, but it's disappeared.
In summary I can see the unit and its moving properly, no slack no fouling, but is a pig to get at with a big air duct in the way.
I can only see one retaining screw for the duct and taking that out makes no difference, I think all the carpets and trim panels will have to come out first and reveal more fixings.

When it's a bit more springlike I'll probably do that to clean all the carpets etc. after winter and have another look.
If I still can't get the duct out I'll probably hand it over to my garage. I'd take all the trim out anyway before doing that.

But a test run logging the pedal position while recreating the problem would be very instructive. I just have a suspicion that it will show the position signals are correct..... So the sooner I can achieve that the better.

[HPsauce]

Could, and if so how, petrol brand make a difference?

For the last few days it's definitely been worse (more reproducible) than normal.
The last tankful I got ( about 2 weeks ago, desperate and on the A12!) was BP 97.

Yesterday, under extreme pressure from SWMBO aggressively wielding a Sainsburys 10p a litre discount voucher, I filled up with Sainsburys 97 in Peterborough. (She did pay )
Since then I'll swear it feels more urgent and no obvious symptoms since in about 4 assorted trips (100 miles total) yesterday and this mornings station run.

[Delboy]

I honestly feel that's clutching at straws, but if it does indeed turn out to be the cause then great.

There was a episode of fith gear where they tested the top brand juices and surprisingly Bp was the worst performing out of the top branded fuels, shell v power nitro came top.

From worst to best there was 5bhp difference in a golf gti so yes fuel is different, but is it bad enough to cause to problems you have had not so sure

[HPsauce]

Originally Posted by Delboy

I honestly feel that's clutching at straws

Well yes and no, more trying to understand the symptoms and see if that helps with a diagnosis.
This is a long-running thread and I noticed early on that changing fuel "seemed" to have an effect, but I didn't understand when and how and it clearly wasn't the whole answer.

Since then I've done loads of things and still got no nearer to a resolution. The recent observation about the response to setting cruise on is new information and I'll investigate that more. The fuel factor is an old one that isn't consistent enough to analyse as for some time now I've been running almost exclusively on Shell V-power.
I might try a tank of standard 95 soon.

[HPsauce]

Originally Posted by HPsauce

I might try a tank of standard 95 soon.

Circumstances forced me into a fill-up with BP 95.
No severe sluggishness since then, but still occasional throttle inconsistencies immediately after a cold start.

Today I decided to redo Throttle Body Alignment, repeated a few times to be certain.
It ran quickly but I noticed that the lower adaptation value, stated by VCDS to be 10% or less, was more like 15% before and after. Any observations anyone?

[HPsauce]

The saga continues............
After no serious symptoms for some time, today I headed off to buy some petrol. After maybe 200 yards from a cold start I turned left slowly at a T-junction and it was sluggish again.
Next junction (where I had to stop) was only 20 yards further so no chance to experiment; after that it was fine.
BUT the tank was pretty empty, showing 0 miles but probably well over 10 litres left. And the first 200 yards were uphill.................

Put in about 75 litres of Momentum (to flush out the BP 95) and it's been fine since.

[HPsauce]

But this evening I managed to do the cruise control thing again.
Hadn't driven for several hours and headed out with a cold engine and just got a "feeling" in the first few yards that it wasn't behaving totally properly.

So, got up to 30mph and set the cruise control. A few yards later braked and turned slowly left then almost immediately right at T-junctions.
It was very sluggish so I let the speed build up gently to just over 25 (it did change gear) and flicked the cruise on. Kick up the backside as my right foot was still a fair way down!
Lifted off smartly as I was still in a 30 limit with the 40 sign just a few yards ahead.

If I can manage it, the next time I'll try to get the car moving faster than the stored cruise setting and see what happens then when I switch it back on.

[Green Goblin]

Just a thought...

Might be worth checking for sluggish flap pivots as per this thread. Maybe dirty and/or sticking?? Bit of a stab in the dark but you never know!

[HPsauce]

And nearly a year has passed with little comment from me, but I got the symptoms again yesterday, rather more oddly this time.
And yes, it has happened occasionally over the last 9 months, I just haven't posted.

We went out for lunch, a 25-mile drive along main roads and M25 to get there (near Egham). All totally normal.
Returned mid-afternoon and being a Friday avoided the M25, so just "pottering" along back roads mostly around 30 or 40mph.

Over half way home, car totally warmed up, drove through Old Windsor then Slough and headed north towards Stoke Poges. After a roundabout got up to around the 40mph limit normally and into 5th gear but then after a little while noticed the engine in higher revs, almost as if in sport mode, but still proceeding gently (pretty sure not on cruise control). The revs meandered up and down a bit then returned back to normal after a little while, below 2000rpm, presumably in top gear.

I did try Sport mode a bit later at similar speeds and while it upped the revs initially it dropped back quite quickly to normal as I was driving gently.

All seems very odd, thoughts anyone?

It's almost 3 years and about 20,000 miles since I had the gearbox fluid/filter changed so maybe that's due another go? And I am planning (not yet arranged) to take the car to Guy sometime this spring (pre Wales/Ireland) for a thorough service and "going over"....

[Architex_mA8tey]

Originally Posted by HPsauce

All seems very odd, thoughts anyone?

It's almost 3 years and about 20,000 miles since I had the gearbox fluid/filter changed so maybe that's due another go? And I am planning (not yet arranged) to take the car to Guy sometime this spring (pre Wales/Ireland) for a thorough service and "going over"....

The gearbox oil change is recommended every 40k miles and perhaps every 5 years if less mileage is done, but have you checked all vacuum pipes for damage, and the correct operation of the manifold flaps and bellows etc, it does sound much more like something like that, or even blocked fuel filter or dodgy fuel?