Seriously at my wits end now...........

Dani_B19

Dani_B19

Audi-sports own special child.
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Evening boys and girls.

In need of some real help before i lose it.

Noticed about a month ago that the cars dropping revs between 400 and 900 rpm when coming out of gear, the revs will drop then come back up to 900 and idle like normal.

So far ive fitted new MAF, IAT sensor, N75, all boost and vac lines are silicone, TB reset, cars idling at 20inhg so no vac leaks.

Thing is the cars driving amazing, made 235 bhp the other day (vag com 188.7 g/s).

Only fault codes have been MAF, thats been replaced today and the Lambda sensor when logging on Saturday but it hasn't come back since.

Can a faulty Lambda cause the revs to drop, heard it can cause bad idle, also my mpg is around 25 when it used to be high 20's to low 30's.

Someone help :(.
 
Can I ask a cheeky question Dan: why do you care? That sounds rude. haha, it isn't ment to, but does it actually cause you trouble?

I have so many people asking me about 'problems' with their cars, that to me, don't appear to be problems at all, merely characteristics of how a petrol engine works...

Perhaps dropping to 400rpm is a little low, but if it's not causing stalling or juddering issues, I'd be inclined to not worry about it.

Perhaps a clean of the throttle body might help it a tad, or cleaning the injectors and FPR in an ultra sonic, I've found that always makes the idle seem silky smooth.....
 
No i get you mate.

Its bothering me because when it drops the car feels like it wants to cut out but just pulls it back before it does.

Yeah think thats my last resort, cleaned the injectors and fpr about 3 month ago but will try for nothing.
 
So you finally fitted a new MAF, as it was very obviously a MAF problem in your last post. Remember to disconnect the battery after doing any repairs, as iv found some fixes don't make much difference until you do this, disconnecting the battery clears any adaptations the ecu has made for leaks, bad MAF readings etc.

Was the lambda fault an actual fault, or too rich or too lean?
 
Not really mate.

Fitted a working MAF from s3paul on here and car still drops revs, obviuosly car ran better in general with his and the new MAF from today in but the rev problem is still their.

Dont know, paul wiped the codes without saving them lol.
 
It was something like ( worded diffrent) B1 S1 lambda malfunction,
As i said dan... Fit a new one, If theprobe isnt reading right the ECU will do silly stuff to try and keep the engine going...
Check how many wires it has?
Are they narrow band or wide band on the early S3?
 
Have you had your intake system smoke tested Dani? you may think you don't have a vac leak but you would be surprised how revealing a smoke test can be...

From the symptoms it does sound like a vac leak but difficult to diagnose without actually looking at the car tbh...

<tuffty/>
 
Mines narrowband paul.

Checked last night and its 4 wirea, tbh it looks proper tatty and like its still the orignial one.

No i havent tufty, need to though but theres no one around here that offers.

Do yo know anyone that does paul?
 
Dani_B19 said:
Not really mate.

Fitted a working MAF from s3paul on here and car still drops revs, obviuosly car ran better in general with his and the new MAF from today in but the rev problem is still their.

Dont know, paul wiped the codes without saving them lol.
Click to expand...

Most garages should have some sort of smoke test facilities tbh... its a general maintenance thing rather than exclusive to turbo/performance cars..

<tuffty/>
 
tested it via vagcom mate.

0 when inactive and 1 when active.

Thanks dave, ill give them a call.
 
Ok might just buy a new one for sake of a tenner.
 
Dan,
I do know of a place that has done a smoke test on my Bora a while ago, If you get completely stuck can always ask them?
I would use it for a day or two, Check the codes. Then measure the Lambda probes readings,
The other fun job is... Checking everywhere for a vac leak,
 
How do you log vacuum leaks with vag com, is it block 032 for fuel trims? Can this bee done at idle? Just struggling to get out on the road and do full logs.
 
Dani_B19 said:
How do you log vacuum leaks with vag com, is it block 032 for fuel trims? Can this bee done at idle? Just struggling to get out on the road and do full logs.
Click to expand...

I can't remember exactly but I can check when I get home. It something to do with resetting the fuel trims then leaving the car to idle for 10 mins and see what they have changed too. If its within a certain range it means you have a vac leak.
 
Nice one mate.

So does can this be done while the cars stationary or does it have to be done while driving?
 
So little update.

Removed and cleaned the TB tonight and fitted a new TB gasket, TB wasnt overly dirty, dont get me wrong it wasnt clean but no baked on ****e etc, anyway fitted back on and i thought id check block 032 to see about vac leak.
Car was solid, left for 10-15 mins and no movement at all, both tables stopped at 0%, after this i reset the TB but havent drove the car, will see how it is tomorrow.
Also picked up my new lambda sensor, will try and fit this week but if not itll be fitted with my full 3" exhaust and DP next week and see if that cures it but fingers crossed.
 
over the past few weeks i have noticed the revs dropping lower than normal when coming out of gear pulling up at junctions.i am watching the rev counter every time now & wondering if i am even imagine it! this has coincide with another unusual occurrence which has happened say four times over the last month.

when starting the car from cold it starts fine as normal but as soon as you touch the accelerator it splutters & nearly cuts out then picks up again straight away & every thing is ok.

the only known issue i have with the car is a faulty exhaust EGT sensor which is being replaced this sat.
 
Be interesting to see if it cures your problem, ive got a lambda sensor to fit when i get my 22m socket, if i cant get it to budge then no biggy lol, new exhaust next week so either way ill know if that helps by next friday.

Just to add, this seems to be clutch related, when stationary earlier, if i dipped the clutch then let of it the revs would flutter and the boost would rise 2inhg from 20 to 18, then settle again, also the clutch would go alot louder.

Possibly faulty clutch switch?
 
Have you tried cleaning the throttle body? If dirt is chocking up the throttle flap during off throttle, idle will be erractic and ecu will try to compensate.

Had exactly the same problem with mine sometime ago and problem went away after I cleaned it.
 
Ordering one today mate :).

Yup, its in actual fact made the car worse, now the car is over/under revving by itself! So god knows why.
 
Have you reset it after cleaning? if not thats why its acting like that, as there are no reference points set,you will have moved the flap in cleaning, so all the settings are lost.
 
I had a similar issue on my old A4. When starting it from cold the revs would bounce up and down between say 600 and 1300rpm, then slowly settle out to a normal idle. Then whenever clutching out for a junction it revs would drop right down to ~400rpm and stay there until you stopped, at which point it would pull itself back up to normal idle.

What cured it for me was replacing the tank vent valve (N80).

I guess you could rule that out by capping off the engine side of the N80, leaving the tank side open and going for a test drive.

I think it was basically acting like a vacuum leak, sticking open or whatever.
 
Yeah ive realigned it dave.

Thats interestig aragon, by n80 valve do you mean the charcoal canister?
 
Not looked at an A3's pipework, on an A4 the charcoal canister sits out behind the wheel arch liner, then a pipe runs thru and connects to the N80 valve, and a pipe runs from this to the TIP and inlet manifold. The N80 opens and closes the charcoal canister off from the engine as and when the ECU wants to.

I think if its open when it doesnt want it to be, it acts a bit like an air leak.
 
audi upgrades
On the s3's i believe i has a vac feed from the throttle body to the canister then it vents to under the wheel liner. Ill try and remove it all over the weekend and see how it is.
 
Dani_B19 said:
On the s3's i believe i has a vac feed from the throttle body to the canister then it vents to under the wheel liner. Ill try and remove it all over the weekend and see how it is.
Click to expand...

The charcoal canister has a vacuum feed from the outlet on the std throttle body and also into the TIP...

Removing all of this typically throws an EVAP incorrect flow fault...
16825/P0441/001089 - Ross-Tech Wiki

<tuffty/>
 
audi upgrades
Yeah will do mate, looks so easy though, have a look on pae 24 of wellys build thread, to begin with ipl just cap the pipe off on the driivers side then see how it runs, them ill rip it all out and tidy the bay up once its running right.
 
Mine should be ok though with it been none wideband according to wellys build thread? If it does through a code up, will affect any of the settings, boost, fuel etc?
 
<tuffty/> said:
The charcoal canister has a vacuum feed from the outlet on the std throttle body and also into the TIP...

Removing all of this typically throws an EVAP incorrect flow fault...
16825/P0441/001089 - Ross-Tech Wiki

<tuffty/>
Click to expand...

I thought this could be avoided by leaving the solenoid valve connected or by wiring in a transistor?

It definitely tidies up the engine bay and gives a bit more room with it all removed.
 
Westy said:
I thought this could be avoided by leaving the solenoid valve connected or by wiring in a transistor?

It definitely tidies up the engine bay and gives a bit more room with it all removed.
Click to expand...

Nope... its a control valve designed to release pressure in the tank etc... not sure how it all works but it will throw a fault code and a CEL if not coded out...

Its not a prob to vent the tank to atmos in terms of its operation.. the evap system is there as a combo of pressure release and emissions...

<tuffty/>
 
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