Audilard

Could someone elaborate on this for me. Is it located in the bell housing or in the distributor? I believe this may be the problem with my coupe and don't want to pay for another tow and mechanic labor so any detailed explanation and help with how to go about replacing this would be greatly appreciated.

90/90Qs

If I'm not mistaken about the part you mention, the sensor is on the outside of the bell housing on the left side. I believe it's just a magnetic pickup and there is a pin in the flywheel to signal it.

QCRAZY

There's a VSS for the speedometer (near tranny). There's an engine speed sensor (in engine). There's a hall sender that would be similar (in the 20v I think it's part of the distributor).

Does your speedometer and/or odometer work?? If so, eliminate VSS.

Does your tach work?? If so, eliminate engine speed sensor.

Does your car have spark?? If so, eliminate hall sender.

Audilard

One day the car will have spark, the next no, so it must be the hall sender.

Ben's e//S2

have you tried pulling the codes?

Audilard

Well, when the car runs there are no codes. So when it doesn't start it has to be the engine speed/position sensor. I've been searching the Rennlist archives and found a couple posts about this. The thing I can't determine is whether or not it is the one with the distributor or somewhere else. The ECU is assuming that because it starts there is nothing wrong with it and clears the codes. DuckMcf reponded to my post yesterday but he doesn't have an email. Hope he sees this and can shed some light.

Ben's e//S2

so i would test that first. although because it's intermittent, i would suspect one of the engine speed sensors (not sure which one, but they're both in the same place mounted on the left side of the block at the flywheel). the hall sender is not typically an intermittent problem, and therefore will produce a fault code whenever you dump them. but you never know, that's why i would look at it first. good luck!

ben

QCRAZY

Usually the hall sender just quits but it's not that uncommon for them to go out intermittantly.

You won't be able to read the codes unless you try when the car won't start. In the Coupe's (excpet Cali cars) there is NO stored code memory. So everytime you switch the ignition off you remove all the codes.

Good Luck!!

DuckMcF

Hi,
sorry for not responding sooner (I'm several time zones away in Australia). If you're anything like me this problem is really getting you down, I was really close to selling the car and wiping my hands of Audi's for ever. For what it's worth i'm glad didn't.

There are 2 sensors in question. The engine speed sensor and the engine position sensor. They are located on the right hand side of the block at the back, below the distributor. On the block they appear as 2 small black pieces of plastic that are connected together and are held in with 2 6mm hex bolts. (that was all from memory as I'm not looking at the car right now, but you'll see what I mean when you look at the engine)

The wiring for the sensors makes it's way up to the group of 4 connectors on the right hand side of the firewall. (My car is right hand drive, so it might be different if yours is a LHD car)

The problem as it was explained to me by my trusty tech is that there was an intermittent problem with one of these sensors (I can't remember which, but I think it was the position sensor). The story was that at startup the sensor wasn't able to give a consistent enough signal for the ECU to be able to interpret. The ECU couldn't be sure when TDC was so it didn't fire. When it's running, the ECU has already found where TDC is and the other sensors provide information on when to fire the spark plugs.

You may have the same issue if it has never failed while driving. If it was the Hall sensor that was playing up the car would miss-fire and carry when running. In my case when I did get it going it drove normally. If it was the speed sensor the tacho would be doing strange things.

Anyway, it's always difficult to diagnose problems via a keyboard, but my feeling is the speed/position sensor is a good place to start if the car runs normally, when it's running.

Good luck
Noel aka DMcF
90q20V

DuckMcF

Hi,
I just re-read my last e-mail and I noticed that I jumbled up my right hand / left hand references. Whoops.

If you're standing in front of the car looking at the engine, the position/speed sensors are at the back of the block, below the distributor, just before the bell housing (I think. Actually they could be on the bell housing itself).

Again standing in front of the car, the wiring from these sensors runs up to the block of 4 connecters on the firewall, to your left.

Also, you may be able to pull some codes, but only if it's just failed to start. If you crank it over and it doesn't start and then pull the codes straight away without turning the ignition off, you may get a relevant code. Most of the other ECU codes are "non-volatile", but I believe that the speed/position sensor codes will be erased if the problem goes away, ie. the engine starts. I'm not sure but they may also be erased if you turn the ignition off as well, but I stand to be corrected on that as I was never able to get any codes at all when my car was playing up.

Best of luck
Noel aka DMcF
90q20V