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I'm new to the forum having just come back to Audi from a TVR and hoped my mechanical niggles would be a thing of the past. I've just acquired a 98' S4 Avant which I am very happy with having owned an S3 prior to the Tuscan.

On Friday I had the Revo upgrade (a complete nightmare of an exercise but that’s another story) The independent who upgraded the car wasn’t at fault but I have found driving it over the weekend there has been an intermittent miss on hard acceleration - normally from lower revs.

The dealer has suggested that the most likely cause will be a lambda probe or an air mass sensor - not the Revo upgrade.

Before I go and spend a pile of money at a fault that didn’t appear to be there before the upgrade can anyone offer any advice - my confidence in Revo is not 100% at the moment.

cheers

scott

Hi Scott,

I too have switched from a TVR to an S4 and will also be going down the upgrade route.

From what you have wriiten the Revo install must have something to do with your misfire, as there was no misfire prior to it being installed. Either that or it has exposed a weakness.

From my past experience with turbo cars it could be something simple such as spark plugs, if you have one in poor condition then this could be exposed due to the engine now generating more power under acceleration, ideally when turbo cars are chipped "cooler" plugs are required, but I believe this not to be a necessity on the S4.

Other than that the sensors that have been mentioned by the dealer could be responsible, but you said that the install was a nightmare? maybe this contributed to it? Ultimately, the problem wasn't there prior to the install, so I would take it back and insist that they at least investigate the issue and at worst revert the car back to standard to see if the misfire is still there.

My S3 pinked after I had the Revo upgrade so I called them and they siad MAF (air mass meter). I replaced the MAF and it went brilliantly after that.
You "could" disconnect the plug into the MAF which effectively makes the engine take it's readings from elsewhere. Then drive it and see if you still have the same issues. Chelsea Mick from the forum did this on his S3 after it was suffering from hesitancy and discovered that his problem was indeed the MAF.
MAF's are now available exchange from the dealers for about £90.

Cheers

Ben

Thanks guys

The dealer quoted me £300 for the air mass meter! Sounds like a nice business - there you go sir, we've upgraded your car now can we have another £300....

Ben - could you give me some directions to the MAF or should I contact Chelsea Mick?

Thanks again

scott

No idea specifically where it is on the S4 but it will be after the airbox on the intake pipework. There should be a connector plug sitting on top of the MAF to disconnect. I'm sure one of the S4 lads will point you in the right direction. Dealers are definately doing the exchange as SiTa got one recently for his S4.
For that money you have to fit it yourself but it's not hard, and to be honest, it's not a bad thing to change any way because if faulty it can cause engine to run lean and harm turbos.

Best of luck,

Ben

The MAF is on the LHS of the engine bay, near the bulkhead and is a cylindrical pipe about 6" long. 5 min job to change it - not special tools - just make sure you don't loose the seals taking the old one off.

Nige.

MAF is a very common problem with the S4....a failed MAF caused/helped my K03 turbo failure. Get it checked by a reputable dealer (AmD, QST, Star etc).

Nige

Can you advise where I can get a replacement MAF at a good price

Cheers

Scott

Scott,

I think Audi Dealers are supplying them on an exchange basis for £80-90.

Thanks for the advice guys - Ive replaced the MAF with a new one from Audi and no imporvement - the car still has a massive itermitatant miss at about 2500-3000rpm - its appears to be when the turbo goes to kick it there is an instant loss of power, large hissing sound like a blow off valve for just a second an then its fine

Im back to the dealer to try an exhange lambada sensor but any other ideas welcomed.

If they cant sort the problem Im going to install the original programme and try another upgrade provider.

Cant say I'm terribly happy with Revo at this stage

Cheers

Scott

Scott,

I have recently been down to AMD and they did a great job! If you have any problems like you are currently experiencing they will find it and sort it out prior to a remap. AMD cost a little more but it's well worth it.

Email me for any details
Julian.

Sounds like a torn TBB - this is very common on S4's with increased the boost levels. You will need to take the TBB out to have a good look at it, as the tear isn't always visible. It should only take you 1/2 an hour or so to check it - the only tool you need is a flat-screwdriver.

If it isn't the TBB (which is the Y-shaped rubber hose at the front of the engine), then it might be the F-hose (to the left and behind the TBB).

I would keep hold of the new MAF for now, as they do fail at an alarming rate.

Nige.

Allblack, u have a PM.

Eric