boxerfan

I assumed it would be under the air filter. After removing the engine cover and the filter box all I see are throttle linkage and lines... Is it under all that crap?

The tachometer works occasionally... usually when cold... I am fairly certain that the sensor has failed. A scan said it was bad and that it was getting some knock. Since the ECU thinks the rpms are at about 1000 I assume the fuel is quite lean.

Kneale Brownson

Do you want the tachometer sender or the engine speed sensor the ECU uses to determine whether it's OK to let the sparking/fueling occur? I have no idea where the former is located on the car. The latter hides behind a heat shield along with the ignition reference sender under the driver side exhaust piping. I think the tach sender is called a "G-22".

audiqv8

I always thought that the rpm sensor was the tach sensor since a bad rpm sensor would cause a no bounce to the tach.

<img src="http://pictureposter.audiworld.com/36396/audiv832a.jpg">


<img src="http://pictureposter.audiworld.com/36396/audi-v8-rear.jpg">

boxerfan

Thanks for the pictures. I managed to get them out once I limped the car up onto ramps. Those connectors are really hard to reach! I'll meter them out shortly. Too bad the bracket is different for them as compared to the I5... oh well... More to come...

boxerfan

One was about 1049 Ohms (black - crank position) and the other was 950 Ohms (grey - RPM) I cleaned them up and reinstalled them because I couldn't get the working set stripped from the Avant out of their brackets. They both measured over 1 kOhm. I'll trade for the new ones in FrankenAudi tomorrow.

BUT... as the Audi gods have seen fit to do so... I have now got a car that seems to be running on just 4 cylinders... What should I look at that I might have dislodged? Oh... I also did a 'no no' and hosed off the guck to see what I was doing under there. Perhaps I have some water in the wires somewhere.

Anyway... I should have some new sensors in a few days and then I can repeat the whole fandango.

For future reference here is what I did:

- remove all the engine cover and air filter stuff.
- remove the metal plate that holds the cluster of wires running from side to side by the fire wall.
- remove the cruise vac. pod and rod and disconnect the vac line.

Now if youy look down in under the cruise pod location there is a cluster of connectors. Crank ref, rpm, and I think O2. They are difficult to remove and reconnect - DIFFICULT! But wait... that's not all... now you need your well practiced contortionist skills.

- remove the belly pan shield.
- peer up behind the EM and you can see 2 10mm bolts holding a shield in place. When they are removed the sensor bracket also comes loose so don't be alarmed when everything starts to fall apart somewhat. To get at those bolts is tricky. There are several angles you can work at so explore what works best for you.

The sensors are held to an aluminum bracket by another 2 10mm bolts.

I'll be sure to take some pictures when I can get back to it. I'm also thinking that using a wire brush to polish up the heat shield may help reflect more of the heat. They are certainly in a poor location. I'm also thinking that a pipe/tube running from the cold air intake runner on the driver's side might help the life span.

audiqv8

I had a crank sensor that metered to be within the limit, but I knew that once it got hot the CKP signal would be gone.

If you went through all the trouble of taking it out then replace it.

Or if you are really frugal then switch the crank position sensor (CKP) and the speed sensor. Better to have a CKP sensor work sometimes rather than a speed sensor. If the CKP sensor goes bad while the engine is running it will remain running, but if the speed sensor goes bad while the engine is running the engine will stop dead.

The only thing different between a speed and ckp sensor is color, one is gray the other is black. BTW you can also use a 5000tq sensor, but the wiring will be longer.

audiqv8

They should measure 1k ohm.

"BUT... as the Audi gods have seen fit to do so... I have now got a car that seems to be running on just 4 cylinders... What should I look at that I might have dislodged? Oh... I also did a 'no no' and hosed off the guck to see what I was doing under there. Perhaps I have some water in the wires somewhere."

Stand up straight and take it like a man.

Most likely you got something wet that shouldn't be wet.

boxerfan

Yea... I know... they get hot and go open. I'll get new ones in there soon. Thanks for all your help.

boxerfan

don't you have to bend over to take it like a man! Sorry.. .couldn't resist.

I could get the lower one unfastened but the upper one I could not get to unlatch when reaching from underneath.

I'll certianly give it a go tomorrow or Thursday... or on the weekend... when I try and get the new ones in.

The car is running better now it is dried out. Guess I'd better get some new wires post haste.

audiqv8

<ul><li><a href="http://www.audifans.com/twiki/bin/view/Audi/NoStartV8">Ignition and Speed sensors</a></li></ul>