Now this is a crazy problem on my 01 A4 Q 1.8 Auto that I will have to address soon as I recently learned that the A/C uses the signal to allow the compressor to function, and that is why my fully charged A/C won't work. When I reset the code for the sensor the A/C works)

I rebuilt the motor last summer and shortly thereafter got the engine speed sensor
Erratic CEL. Replaced the sensor and noticed my old one looks to have been rubbing the pickup disc that is mounted to the crankshaft. My theory is that maybe having the crank on the bench or something else, bent or warped the disc. I don't want to pull the motor again so I think I will attempt to drop the oil pan and see if I can straighten it out.
Other than the CEL being on, the problem has not really affected the car enough to warrant me getting off my butt and fixing the problem, but now that it's getting hotter out, The A/C was a good incentive to fix the car.

Has anyone else ever had this problem, and if so, what did you do to fix it.

Thanks,
Dave
Waldorf Southern MD

http://picasaweb.google.com/EckFamil...eat=directlink

 

that disk you are talking about on the crank is called the trigger wheel, and it is pretty substantial, you would have to drop the crank from quite a distance in order to bend it. its possible that something got caught between the trigger wheel and the sensor and chewed it up?

when you replaced your main bearings did you plastigauge everything when you put it back together? did you replace the crankshaft all together or use the same one? which main bearing was that that was worn so bad? it looks like the center one (#3)?

 

Yes, I plasti gauged the crank and everything was in spec. It was the center Main bearing and believe it or not, the crank was unharmed. There was a lot of bearing material stuck to the crank, but was painstakingly polished off. I guess it was caught in time and that's why they make the bearings out of softer metal.

The rebuild took several months as I worked on it in my spare time, so anything could have happened to the crank in that time.

Thanks,

 

Well, I went to drop the pan but noticed the cross member runs right across where the trigger wheel is, so I would not be able to see it well or be able to work on it.

Is there anyway to add a crank sensor/pickup wheel (aftermarket) that can be added to the crankshaft pulley on the outside of the engine? I want to avoid pulling the motor if possible.

Thanks,

 

you cant really replace it anyways without removing the crank from the car.


that toothed gear around the end is the trigger gear, i have dropped one of those cranks (one im not using) off my workbench onto concrete and it left an impression of the teeth without damaging the wheel. unless some foreign object got in there while the engine was running or you were prying against it for some reason with a crowbar i dont see how you could have bent it.


you can take the sensor out and look thru the hole with a flashlight and see if the wheel is messed up. it could be as simple as a broken wire going to the sensor or the sensor not screwed in far enough to the block.

you said you rebuilt the motor last summer, what exactly did you do? it could also be possible that your a/c issue is not related to this problem at all.

 

Thanks for the reply and pics. My trigger wheel is different than that one. Mine is made out of stamped steel, angled at the end, and their are not teeth, just square holes punched out of the flat steel. Not as sturdy as the one looks like in the picture. I may have dropped the crank at some point and warped or bent the wheel and now I get an "Implausible signal" error
when I hook it up to Vag-com. The car starts and runs, and I have been driving it with the error for months now hoping I wouldn't have to pull the motor just for this.

When I reset the CEL using Vag-com, the A/C works momentarily, until the engine speed sensor error code reappears. This led me to believe that the AC requires a signal from the Engine speed sensor.

I tried to look through the hole, but was not able to get a good angle view due to ohter items in the bay.