Hello all,

Long time reader, first time poster!

Can someone please help with advice on self diagnostic checks/repairs for an over-revving issue I'm having.

Car details:
Audi A4 (B7), 2.0T quattro 6 speed manual, S-line, standard everything..

The history:

- Noticed the car revs dropping and/or climbing rapidly as soon as the clutch is engaged.
- Cruise control stopped working
- Ran an autoscan VAGCOM diagnostic check with the following errors:
1. 001796 - Clutch Switch (F36) P0704 - 004 - Implausible Signal
2. 00819 - High Pressure Sensor (G65) 07-10 - Signal too Low - Intermittent
- Replaced the clutch switch (easy job and thanks for the forum help on this one). Cruise control works fine.
- The "Revs dropping" rapidly is no longer occurring, however the engine is still over revving as soon as the clutch is engaged. (i am definitely not keeping my foot on the accelerator longer than i should be - checked that it wasn't just me!)
- I have cleared the fault code for the clutch switch
- I have completed a live scan of the relative throttle position whilst driving and am noticing a spike in the revs particularly when shifting 1st to 2nd and 2nd to 3rd.

The over revving problem is more pronounced when i am heavier on the throttle. Hardly notice it if i drive like grandma..

I am getting the aircon re-gassed this week (it seems to have no cooling capacity at all now). Could the two be related somehow? A vacuum leak somewhere causing the throttle to stick open?

Anyone had these sorts of issues before?

Apart from the over-revs, the car idles fine, delivers power accordingly and runs well..

Before i take it to an incompetent Audi service centre, can someone please help with other checks i can do myself.. I could guess a couple of things, but before i go poking around for no reason, i thought maybe the experts in the community could suggest a couple of things/tricks they may know of..

Thanks in advance for all your help!!

Nem.

 

Interesting that the switch didn't fix it completely

 

I was hoping it was only the switch!

Now I'm thinking it has something to do with the throttle itself..

I might try clean out the throttle body, see if that helps.

Will advise how things go..

Cheers.

 

Hi Nem007

were you able to resolve this problem somehow?

thanks
Chris

 

Ok to make sure I understand what your saying... When you press in the clutch pedal in to release the clutch, and your foot is completely off the gas pedal, the revs increase?
Or is it when you release the clutch pedal to engage the clutch and begin to accelerate the RPM's climb quickly without any noticeable acceleration?
The A/C is most likely due to your high pressure sensor fault saying you are low on refrigerant.

 

Hello gents,

Firstly i'll give you an update to where i am with diagnosis and then best try answer your queries.

Regarding the air-con, we found out the hard way that there was a substantial hole in the AC condenser - parts and labor at the mechanics $700. An aftermarket OEM condenser can be sought for about $150, so I am considering doing it myself, however with cooler months approaching i might leave that until later. Good to see the sensor is working!

The over revving is still occurring, only notice it between 2nd and 3rd. Sincityaudi, this occurs, as you say, when the clutch pedal is pressed and i am off the throttle, the revs climb for a split second and stay high until i release the clutch..

Saying this, the car is running fine in all other conditions.. now that i'm aware it does this, i guess i have adapted.. I am coming up to my major service interval 90,000kms, might have the experts look at all these issues see if they have a solution..

I have heard that this problem is occurring with other peoples cars too.. ECU maybe needs an update/change? Might give me a few more kw's too!

thanks...

 

Hey Nem007,

Do you have an update on what this ended up being? I've been struggling with the same issue that you have described, and so far I've replaced both clutch position sensors, and the PCV valve... maybe just go and do an Audi 90,000KM service is next up.

Cheers!

Mart

 

Hi guys,

It's been a while since my last post and a few things have surfaced since then.

Firstly, i may have resolved (or minimised) the issue about over revving, or at least the car is sunning a lot smoother and delivering more power. Quite an easy fix too.

Following on from my last post, i bought a condenser from eBay ($100), checked the fitment on their charts, they guaranteed it was to OEM specs, sure enough it was.. one win!

The 90,000kms service: I've done the timing belt kit (all the rollers, tensioner, water pump, seals and so on).. Whilst it was in the shop, they found a fault code on the diverter valve.. They also mentioned that was why i could hear the turbo "fluttering".. generally, this shouldn't happen and can damage the turbo because the air is traveling back into the chamber retarding the blades (yeah it sounds cool, but i'd rather have a healthy unit!).. They also said this could be the reason for the over revs, as the air isnt being diverted to where it should be and possibly making the throttle stay open longer than it should.. Not to mention the power losses from all that pressure leak.

Another suggestion they made and this is a common problem, was to replace the pressure control valve (PCV), this helps the car idle much better and generally run smoother.. (As you have already changed out mcfly2500)

I fitted both.. picked the car up and sure enough, feels much more responsive on the throttle, seems like its delivering more torque at the lower end.. Now, the over revs have all but gone, however between 2nd and 3rd gear, under load is when it is most noticeable, there is still a slight delay and the revs stay high.. Not sure what to do from now.. The issue doesnt concern me as it only appears to surface when under load, 95% of the time i drive the car relatively easy.

The fault codes are clear.. so i'll just have to monitor it and report back to you guys soon..

whatever the case, these two small upgrades are well worth doing.. both OEM parts are problematic and have been upgraded to more robust designs. Highly recommend you doing it!

Europaparts are very competitively priced compared with other online stores, reliable delivery and great service. Get on them..

Links below.. Read the product descriptions:

EuropaParts.com: Diverter Valve (2.0T, Updated "D" Version) - 06H145710D
EuropaParts.com: Pressure Regulating Valve (PCV, Revision N) - 06F129101N

Hope that helps!