Erratic throttle response when cold

[Bandycoot]

I've been getting the very same problems on my FL S8. Just to add a bit more confusion into the mix; have you checked for air leaks. Since my problems started I have found a few air leaks in the induction system and have replaced the two rubber elbows on the air box and throttle body and now I feel I have air leaks in the manifold.

Like you I've changed my MAF and a few other things without any result.

One thing you can do which may help is to give your throttle body a good clean with some carb cleaner. Refit with a new gasket and see what happens. You may have to do a throttle body adaption afterwards but this is a simple process.

My problem doesn't happen that often now as I think I'm getting close to solving this once and for all but a trick I use when it does occur is this: stop the engine then turn the ignition back on without starting the engine and leave it for at least 30 seconds before turning the ignition off. Turn the ignition back on and start the car. During this process DO NOT TOUCH THE THROTTLE PEDAL or else it won't work. If this procedure works for you then it could indicate a problem with the throttle body.

Hope this helps.

Steve

[HPsauce]

Thanks for those observations, and yes I'm still getting it at times.

The thing is it goes away immediately if I blip the throttle, so no need to do that procedure. And I have done the TBA process (using VCDS) a while back, it all went smoothly and nothing really changed.

Is it possible to access the throttle body directly on the car and give it a bit of carb cleaner squirting there? I'm not really quite sure where it is.
The air pipes I'm pretty sure are fine.

[HPsauce]

Well it happened again today, when the car was totally warmed up near the end of an 80-mile run.
I was leaving the M25 after several miles at "motorway" speeds, down a reasonably long slip road, so braking gently for maybe 200 metres to a roundabout under the motorway.
At the bottom I had to come to a complete stop as there was traffic (one small car!) on the roundabout, I then entered the roundabout and took the next exit, following it.

As I moved off I could tell it was misbehaving again, but it's a very quiet junction with nothing behind me or even in sight apart from the car I'd waited for, so I just lets things develop.

It moved off quite gently, even though my foot was down a reasonable amount, revving up to maybe 3500 before changing up a gear then carried on the same. It was a bit like driving a manual car with a slipping clutch. It was in full auto mode so I don't know what gears it used.

After the gear change I got bored and "blipped" the throttle, reverting everything to standard behaviour and overtook the little car (empty dual carriageway with 70 limit).

Does this give any clues anyone can interpret.

Fuel today was Sainsburys "Super" (97?) as we had a 10p off per litre voucher to use!

[HPsauce]

Today I replaced the Fuel Pressure Regulator, as discussed in this thread: http://forum.a8parts.co.uk/showthread.php?t=8351
I did buy a "cheap" Meat & Doria one (MD75013) but am prepared to get the OEM Audi one in due course if that is unsatisfactory.

Although I did release the pressure by undoing the 17mm nut on the fuel feed pipe it wasn't actually pressurised, though the car had been unused for nearly 2 days and it was in the cool of the early morning.
Getting the old FPR out was a bit of a struggle, it was very tight. Mole wrench to the rescue, with lots of wiggling and rotating. The new one went in fairly easily with just a firm push and a twist.

Turned the ignition on and could briefly hear the fuel pump refilling the unit until it stopped. No leaks evident so started the car and it was fine.
Went for a short drive and all seemed OK and suitably brisk, but the symptoms are intermittent so only time will tell.

[Architex_mA8tey]

Originally Posted by HPsauce

I did buy a "cheap" Meat & Doria one (MD75013)

is that Meat & 2 VAG?

[HPsauce]

Hmmmm, well it's a bit different, but I've only done a handful of short runs (1 to 3 miles).

Once moving it seems as normal, but:
Starting is different, less "instant" and in one case (when warm) took a few seconds to catch. What are other people's D2's like to start?
I've noticed one possible brief "higher revs but sluggish progress" event after pulling out at a T-junction when the car was warmish from earlier use but had only been driven about 200 yards that time.

Starting, after I changed the coolant temperature sensor, was always quick and "violent" with a short burst of high revs (over 1500rpm) before quickly setlling down to idle.
Now it takes a bit longer but just goes straight to normal idle speed after a tiny initial blip at maybe 1000rpm.
Maybe fuel pressure was too high before and isn't high enough now? But "on the road" it's as responsive as ever - I had a little "play" this morning to check.

[steamship]

Have been reading this thread and noticed that no one else seemed to experience a similar problem. Since the meet in June, I've been focusing more on trying to sort out my garden and have been not paying attention to the car. I was out the other day, and experienced the exact same symptoms. I live down a very rough lane so I tend to crawl up it anyway. When I went to move onto the road, there was lots of revs but very little movement. It was almost as if you were driving with the handbrake on. It was only a short 4-5 mile run, but I noticed the same sluggishness several times, usually around junctions. I know I still have issues with SAI and fuel mixtures, but the one thing I did discover was that I was low on oil. Very low in fact, as it was just below the minimum mark (told you I hadn't been paying attention to the car). Anyway, I topped it up and the following day when I was out on another short run, it was as responsive as ever. Don't know if this is significant or not, but as you've experienced this on a number of occasions, it if was solely a low oil issue, I'm sure you would have spotted it before now. Mine is also LPG, so it doesn't appear to be fuel/petrol related.

[HPsauce]

Originally Posted by steamship

When I went to move onto the road, there was lots of revs but very little movement. It was almost as if you were driving with the handbrake on. It was only a short 4-5 mile run, but I noticed the same sluggishness several times, usually around junctions.

That does sound similar, though I can't see how engine oil level would have that effect.
I've recently had a full major service (cam belt, water pump, the WORKS) so would be very surprised if the oil level was wrong. No warnings, though I haven't checked it lately.

[HPsauce]

I'm still confused by this, it's certainly a bit different since I changed the FPR. I was going to swap it back but have had problems with the other car (Focus - fuel pump fuse blew!) so I'm not touching the Audi at present as I am relying on it.

I now seem to have 3 modes of operation:
1. Normal (most of the time)
2. Sluggish, rare as reported above, resolved by a quick "blip" of the throttle
3. Scalded cat!

The latter is new. Just using middling throttle (definitely not flooring it) it will sometimes take off much faster than I'm expecting. And you can really feel the power kick in as the flaps open at higher revs.

Forgot to add, starting is still a bit "iffy"; I find that if it doesn't catch quickly I turn off and try again and it's usually OK 2nd (or 3rd) time.

[HPsauce]

Finally decided to swap the Fuel Pressure Regulator back as I still keep getting little glitches at inconvenient times.
Just been for a little drive round in road conditions that often trigger it and all seems OK so far. At least I didn't break the old one getting it out with a mole wrench.

This time I used a little rubber-surfaced gadget we have for getting the tops off jars, that is much more gentle and enabled it to be wiggled out very quickly.

There's a good discount at ECP at the moment so if I want a genuine Bosch one they're only about £60.