captainjp

I have no idea where to start.

B7 Quattro Tip

Recently car has been bucking under acceleration
Thought it was a tranny issue, but no codes

Here's the strange thing:
When the bucking happens, the temp gauge drops to zero, then slowly eventually climbs back up.

Also, the PRNDS indicator flashes very quickly. The number indicating the actual gear disappears!!
(Not the red screen of death)

Brought it in, no codes except for low fuel pressure. Mechanic seems to think HPFP.
(Yes, Cam follower had been changed previously)

Had him change the CTS, but still no joy.

I have a video, and a still of all of it.

Please PM with your email if you wanna see them, and have any ideas.

Thanks!!

captainjp

Oh, and i just wanna clarify. The PRNDS doesn't continually flash as if it were in limp mode.

It literally flashes for a microsecond. The pic I included shows a still of this phenomenon.

It was taken from a video of the event going down.

Thanks again!!

SkyMedic

What seems to be happening there is not merely one system issue. It's a general electrical problem.
This may also be why ther are no specific error codes logged after the event.
The fact that multiple sensors / indicators are malfunctioning leads me to believe it may be a grounding issue. Most likely onthe instrumetation / ECU rather than on a sensor.
Check the grounding for the instrument display, as well as the electronics module just behind the engine bay firewall. Another alternative to try would be to disconnect the electrical connectors to the ECU and instrumentation, spray them with something like LektroKleen or a lubricating switch cleaner, which would leave a corrosion-inhibiting residue, allow it to dry then re-connect and see what happens. I had similar jarring with a Renault Megane and it was solved by resolving connectivity at the ECU, in the manner described above.

Good luck

captainjp

Worth a shot. It's a very strange phenomenon. Also wanted to mention that when the temp gauge thing happens, the radiator fan kicks on and blares.

The cold weather here in NYC has not helped at all.

Thanks for the reply

SkyMedic

Check the temperature sender unit on the block.
Not sure whether there is just one or two.
Older engines had one for the temp send to the ECU, and another for fan control.

ECS Tuning-Audi

Could also be that the ECU it's self had gotten wet. I've heard of peoples water box's leaking allowing water to enter the ECU box. Once the ECU gets exposed to moisture things start to act whacky.

Jason