S6 5 pot turbo motor engine speed sensor

BB · November 28, 2011, 03:27:40 PM

I have a car here that wont rev out, it runs smoothly but has no power. Codes say its the engine speed sensor.
I have however unpluged the two flywheel sensors one at a time and the car wont start, pluged back in its starts first pop.
Also did this to the sensor at the front of the motor with the plug at the end of the injector rail.
Anybody know which one for sure of these three is the engine speed sensor?
Any other ideas?
Thanks

RS ZWEI · November 28, 2011, 03:32:32 PM

IIRC with my old VR6 the engine speed sensor came up on the scan when the car wasnt running.
I think its the same with my RS2?

wilco · November 28, 2011, 05:29:11 PM

Nic some models if not all give that error as when the engine is not running there is no signal from the engine speed sensor, so logs it as a fault. I was caught with that a while ago with an ABT engine. Technically it's a fault by not an error, if that makes sense. It seems to be around the '93-'96 era fo ecu's. No doubt there'll be other know-it-alls who will want to correct me...
However for BB, it may be that as revs increase the signal is getting confused. In saying that, the sensor itself is pretty simple pulse sensor so they don't go crook often.
The one at the front is often a timing sensor, one of the bellhousing ones is the rpm sensor but then if there are two in the bellhousing one the other is timing, ie TDC. Is it an AAN motor?

5-pot · November 28, 2011, 05:44:50 PM

I always thought the RPM sensor was the one on the bellhousing counting flywheel teeth. Other other is the TDC sensor and the target is usually a pin on the opposite side of the clutch, on the flywheel. Try and find a known good sensor and swap that in. It's a solid state sensor so they don't go wrong often but oil, water and heat take a toll on things. Especially electronics.

I'm not familiar with the AAN though. Do they have cam position sensors on the head? It might be getting engine speed info from that.

BB · November 28, 2011, 06:09:25 PM

Thanks for that info Nik and Wilco

I think your correct its logging that code as I read the codes with the ignition on but no engine running.
It also give a charcoal solenoid code but I doubt that would make a difference.
Thing is I did disconnect them all one at a time and the car would not start with any of the three disconnected so they must be working.

i have removed the old fuel filter as it was reported that the car had also gotten hard to start and felt short on fuel so hope this maybe works out.
Or maybe its got a boost leak?
I replaced the plastic bypass valve thing and the new one was way harder to push with my finger.

I must say this old beast has got over 300kms on it and seems to pretty much all still work

I think they are one of the good models.
Ill report if the filter makes it go better.

RS ZWEI · November 28, 2011, 07:48:01 PM

Boost leaks normally make the car have an uneven idle.

00quattro00 · November 28, 2011, 09:11:54 PM

The one at the front is the cam angle sensor, then there is the two on the bell housing, Im not sure which is which, it will probably be the same sensor used on other engines, whats it boosting to?

BB · November 28, 2011, 09:59:56 PM

No boost at all. Smooth but gutless as.

00quattro00 · November 28, 2011, 10:01:45 PM

Quote from: BB on November 28, 2011, 09:59:56 PM
No boost at all. Smooth but gutless as.

Waste gate not closing for some reason?

BB · November 28, 2011, 10:11:28 PM

I was thinking that but normally you can hear the turbo spooling but no boost?

beeker · November 29, 2011, 06:34:42 AM

Probably no help, buy when my speed sensor failed on my B7 RS4, it wouldn't start at all. Cranked ok, but no fire.
PS took 2 weeks for the part!!! And that was with a fancey pants audi warranty.

BB · November 29, 2011, 08:22:53 AM

No that helps Beeker as that's what I believe also if the speed sensor was faulty the car would not start.
As I say I have disconnected individually all three sensors and the car won't start but then does when I reconnect them.
I am going to do the fuel filter today and I will then look at the waste gate if that's not the cure.

SimonS2 · December 03, 2011, 02:38:12 PM

S2 gives speed sensor error if plugged in to VAGCom and not running.
When you say 'won't rev out' do you mean revs are restricted, or it revs but no power?

qta4 · December 03, 2011, 05:52:33 PM

Cam angle sensor on my 1.8t causes similar problems and engine will run unplugged.

BB · December 03, 2011, 06:35:26 PM

Thanks guys.
I have replaced the filter and it runs better. It has a boost leak. I am sure it would run well if the leak is fixed so I am going to have to strip the intake AND exhaust down and fit gaskets etc.
I can hear it leaking boost.

BB · February 10, 2012, 05:51:22 PM

This old post is still cursing me.
After a lot of peril we are back to the same place. No power.
Its starting and running fine, No codes. But no power.
We have held the brakes on and boosted it in gear, the intake hoses definitely swell and get hard to push , I will fit a gauge.
Things that have been done.
Exhaust welded, waste gate repaired and holds 10psi is what I was told. Inter cooler pressure tested no leaks.

Do they have a lifter pump? Could it be fuel? Fuel pump? Air flow meter? Again no codes, they all came up as I had unpluged everything and turned on the ignition but when i cleared then and did a boost run again no codes came back up.
O2 sensor? Faulty ECU? It just goes flat feeling when you try and power it, it does also make a turbo wooshing sound but after looking under the bonnet on boost I dont think there is a leak in the hoses etc.
I replace the waste gate. Turbo all cleaned and is ok, new gaskets mostly.

And lastly where is the engine ecu in a S6?

00quattro00 · February 10, 2012, 06:02:04 PM

Ecu is under the carpet in the passenger footwell

BB · February 10, 2012, 06:13:25 PM

What do you recon Basil?
Ive done like 3 grands work to the bloody thing and now I want to get it finished.
I stripped the whole intake including turbos off it looking for the leaks and found some issues like a cracked manifold then all the bolts snapped when refitting it, head off all studs done new valve guide seals head set was bloody pricey did the steering gater holy hells a poppin.

Its always Audis that do this too me

Mind you I don't get to work on much old Jap turbo crap and I never would allow myself to get involved, it would be even worse.....I have done some work on them actually. Subarus and others

00quattro00 · February 10, 2012, 06:16:01 PM

I say pull the engine out and send it down here

Have you tried another maf?

BB · February 10, 2012, 06:23:20 PM

Yea you would say that.
No I haven't tried another MAF. Maybe Scott would let me borrow his..........maybe not, this person would definitely let somebody borrow his if their S6 had this issue

Oh another very important clue is that it did it suddenly apparently , plus it did it then it got better then it did it again and stayed bad.
I tried blocking off the idle valve as that did click open and closed but there was always a small gap and you could blow though it even when closed, It still didn't perform with it blocked off tho and was hard to start and wouldn't idle properly.