Stuttering and hesitation at large throttle openings

[Kodiak]

Guys, no one mentioned gas in canada and US are (RON+MON)/2 spec, not RON????????


98 RON equals to 93.5 R+M/2, so it's definitely not a fuel quality problem IMHO, unless the pump was selling crap, but Sunoco 94R+M/2 is good stuff usually ;-)

HTH,

mihnea

Yeah, that's what I thought. Thanks.

I've got a leak test kit on order. Here's hoping the leak's an easy fix, once I find it.

[jeroen]

I've got more or less exactly the same problem!!! so ill be reading these pages closely :-) thanks for all the advice up till now.
I'am an audi dealer mechanic as well butt olny see newer audi's and people here have a lot of experience with trouble shooting on this type engine! so as forr the audi dealers they will mostly start from the beginning and now you get some good advice in wich place the problem most likely is!

[S2sedan]

Great stuff. Thanks for that. I will start searching for leaks, and Lee.

The car is certainly not 'undriveable'. It's perfect except when approaching WOT.

So a hose is the most likely culprit, then? And the leak is most likely between the air filter and the turbo?

If I just run the car and have a good look, what are my odds of finding the leak? Decent, or is that a waste of time?

Forgive me if this is a stupid question (but that's why I ask before doing): How 'bout holding a lit cigarette up to the air filter and looking for smoke coming out of the leak?

Mine has same symptoms and I cleaned the MAF, did not solve I had to change it. It was perfectly driveable but gas went away fast ...

[Kodiak]

Hmm, so it could be the MAF. I guess if I clean the MAF and the boost kit shows everything's cool, then a faulty MAF is likely?

Just in case, where's the best/cheapest place to get a new MAF? Ebay?

[Kodiak]

I just tried to remove my MAF for cleaning, but I haven't got the right tool. What kind of fasteners are holding that flange to the airbox? It was a bit dark for me to see. Are they Torx? What size?

Thanks!

[JPL]

I just tried to remove my MAF for cleaning, but I haven't got the right tool. What kind of fasteners are holding that flange to the airbox? It was a bit dark for me to see. Are they Torx? What size?

Thanks!

They are Allen head bolts, can't remember what size, try 4-6mm. They may be full of crap, give them a scrape out first.

Graeme.

[Honahon]

"I'm considering dropping in a bottle of octane boost just to confirm or rule out fuel as the problem."

What is this? is this some thing you put in the tank to blast out any petrol germlins?

[jeroen]

bottle of octane booster! this changes the octane number in you tank of fuel! I heard you could get up to a race spec of RON 102/101 instead of the normal 98!!
witch means detonation would not occure as fast.

If you live in a country witch overall poor fuel (low octane)and high temps than this can make a big difference.

[Kodiak]

Yes, I was considering dropping in some octane booster to see if that cured the stuttering problem, but I'm now quite sure that the fuel isn't the problem.

The octane booster, like the name says, is a can of stuff you dump into your tank to raise the octane level. But I read somewhere on the 'net (perhaps not a reliable source) that a can of octane booster has relatively little effect on a tank of fuel. It might, for example, raise your octane rating from the pump's 94 to 94.3 or 94.4. That's not much of a difference.

So those are allen heads, eh? Anyone know what size? They look like at least 6mm, and they are full of crap. I will have to clean them out a bit. Glad to hear I'm at least looking at the right thing, and not trying to unbolt the electronic lipstick dispenser motor.

Thanks!

[jeroen]

I also read what mihnea told that 94 or 93.5 octane in canada is same as 98 in europe! so that won't be the problem.

[S2central.net]

Try throwing in a batch of MMT based octane booster to see if problems go away.

Never forget that we UK folks talk about 98RON fuel, and the N.American folks spec fuel as an average of RON and MON. MON is actually a better indicator of fuel performance under load. US spec 94 fuel should be as good as UK 98RON.

Suspect an air leak or MAF / connector problem. Check earth points around engine. Pull fault codes.


Paul

[Kodiak]

Thanks for that, Paul.

I'm going to clean the MAF shortly (after I buy the right allen driver -- do you know what size it is?).

What could be wrong with the connector? Should I just clean it with the same stuff I'm using on the MAF? How do I disconnect it? It's got that metal clip on it and I don't see how to undo it. I don't want to damage it by doing it wrong.

Check earth points around engine? I know what earthing is, but what are earth points, and what am I looking for when I check them?

Fault codes, right. I'll search elsewhere in the forum to see how to do that.

Cheers.

[Kodiak]

Update: pulled fault code 2413 last night. Seems to confirm what we already thought.

Can anyone tell me the best way to go about cleaning the MAF connector? Is it safe to spray it with alcohol, like the MAF?

I haven't yet got 'round to cleaning the MAF or testing for a boost leak, but I sure hope that doing those things identifies the problem. I'm getting increasingly frustrated being relegated to the first 75% of throttle travel.

In other threads, some people have suggested that this code points to a malfuncitoning Lamda probe. What is a Lamda probe, where is it, and what does it cost to replace?

Assuming for the moment that my car has no boost leaks (not yet confirmed), is there any way to know if it's the MAF or the Lamda that's bad besides switiching them out in trial and error?

Many thanks for any help on this sad, sad subject

[auditude]

Update: pulled fault code 2413 last night. Seems to confirm what we already thought.

Can anyone tell me the best way to go about cleaning the MAF connector? Is it safe to spray it with alcohol, like the MAF?

I haven't yet got 'round to cleaning the MAF or testing for a boost leak, but I sure hope that doing those things identifies the problem. I'm getting increasingly frustrated being relegated to the first 75% of throttle travel.

In other threads, some people have suggested that this code points to a malfuncitoning Lamda probe. What is a Lamda probe, where is it, and what does it cost to replace?

Assuming for the moment that my car has no boost leaks (not yet confirmed), is there any way to know if it's the MAF or the Lamda that's bad besides switiching them out in trial and error?

Many thanks for any help on this sad, sad subject

For the connector, I would use an electrical contact cleaner like DeOxit.

http://shopping.netledger.com/s.nl/c.ACCT113328/sc.2/category.188/.f;

[Kodiak]

I managed to clean the MAF. More of that here:

http://www.s2forum.com/forum/showthread.php?t=993&page=2&pp=40

The stuttering at large throttle openings is now less violent. It no longer feels like the car is eating itself, but the problem's still there. Next step in the plan is a boost leak test.