dillon410021

I have heard some mixed opinions on the tack bouncing on start up. On my car, the tack will bounce a little on start up but it will not do it all the time. From what I have searched, this would mean the reference sensors are going bad right?

thanks in advance.

minho78

Dillon I don't pay much attention to my tach, but the times I did my tach never bounced either and my reference sensors were done a year ago.

dillon410021

I am wondering because I will have the intake manifold off in a couple months and I believe the sensors are original. I also think the o2 sensor is original

ramius665

Not knowing if they have been replaced sounds like good enough reason to do them to me. I'm replacing every sensor on my engine just so that I know EXACTLY how many months/years and miles are on every one.

alxdgr8

tach no bounce + no start = jiggle ref. sensor wiring
My tach bounces everytime my car starts...if it doesn't bounce then it means my car isn't starting, so see above

Darwantae951

I have no problems with my S/R sensors and my tach does not bounce on start-up.

odb812

my reference sensor harness was bad under the boot on the dme side of the connection at the back of the intake manifold. my car didn't start and my tach bounced. i replaced the speed and reference sensor harness with the LR part and it's been starting fine since and the tach hasn't been bouncing. i ziptied this harness to the firewall rather than connecting it back to the intake manifold to keep the new sensor from wiggling cracks in the wire insulation.

joster86turbo

what does it mean if the tach flips and pegs past 7 all the time?

MM951

The tach bounces on all 944s I have owned or driven. The bounce is only ~200rpm if that and if your car starts quickly you may not notice it, but they all do it.

ehall

^^^Yep.

schip43

Yep on mine no bounce = no start.

951Tom

Replace the shielded wiring harness all the way back to the DME and replace the sensors. This cured my random no start problems. When the no start did occur, the tach would not bounce on my 951.

schip43

I replaced the sensors and the harness still have the problem very random usually on a hot restart. Any ideas? Car is in storage for the winter so I have time to investigate.