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HELP A5 3.0 TDI RPM Fluctuation When Stop at Traffic Light

10K views 20 replies 6 participants last post by  lovea50c 
#1 ·
Hi guys,

I am new to this forum. I have a 3.0 TDI A5 Quattro Cabriolet.

I am bit desperate for this RPM fluctuation issue. I am having this issue, whenever I come to a stop at traffic light, the engine rpm will jump up from 600 to 800 and back to 600 again and a jerk/vibration can be felt. I tried to scan with ODIS (as I do not have Vagcom/VCDS) as it wasn't showing any fault code.

Then I was told by a mechanic that it is a common issue for diesel car to have this throttle body issue. I then look up on ebay and found one aftermarket throttle body/valve from China that cost about $150 USD, same part number. It just arrived yesterday and I installed it myself with success. So I went for a road test yesterday and it was all good, rpm just stays there around 600rpm when stopping at traffic light. I thought the issue was resolved and was quite happy with that.

However, this morning when I drove my car to work, sometimes the rpm just went from 600 to 635 and back to 600 again and a slight vibration can be felt so I thought could be normal but then after when I finished work and drove back home again, this time the rpm went from 600 to 450 and back to 600 when stopping at traffic light. Now the rpm went lower instead of higher.

I am no clue what is causing this problem. Can someone please let me know what to do and please save me for sleepless night as it's always in my mind?

By the way, I tried to clean the mass air flow sensor. Also one thing to mention is I did not do any adaptation/basic setting after installing the throttle body as I could not find any of this function in Odis so I thought it is not necessary.

Thank you very much in advance!

Have a good one!
 
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#2 ·
Strange. Diesels are normally quite steady on idle.

So did this fluctuation occur after you cleaned the MAF? Also, what did you clean it with?

It could also be an EGR issue, where it is opening or closing with no complete control.
 
#4 ·
Ello mate and welcome on board. I am sorry but mine is petrol so I dont know, but I would comment that you should have a look at the automatic gearbox oil level. Sounds wierd I know BUT mine also used to rev up and down as you describe until a mate suggested the oil level, and I found that the car is VERY sensitive to the auto box oil level. Just an idea.
 
#5 ·
Hi Simon,

Thanks, how are you?

Is yours 7 speed tiptronic? So your transmission oil level was low and filled it up and the issue is gone? Did you do it yourself or have someone to replace or fill up for you?

Good point, I will have a look and I hope to find instructions how to replace the transmission oil and what kind of oil to use.

Cheers,
 
#14 ·
Hiya!



Mine is the 8 speed box as the car is an early one, 2008. I use a wonderful independent guy and he does the work for me so I am sorry I did not see him do it, he tells me that the car must be on a level and even a quarter of a litre makes a difference. Good luck!!!
 
#6 ·
Also one thing to add is recently the rpm went so low in 1st gear while waiting at traffic light and the engine just stalled.

I really could not think of the reason behind this. I was hoping it will come up with some fault code so atleast I have a clue but no it hasnt shown up any yet
 
#8 ·
Could be the reason, but I would assume you would get missfire and engine faults etc., I've had really similar thing my previous car, but it was petrol, cleaned mad, changed all sorts of parts and it turned out to be an ecu and once that one was replaced it went back to normal. Id say try to get cables back together maybe and see where that leads you. Can't figure out why there is no missfire though
 
#9 ·
Please see the photos of the wiring to fuel injectors.

So X3me, what fault code did you get to lead you to replacing the ECU as it could be expensive, unless there is an aftermarket one?

Yeah the reason I got frustrated is that, there are numerous times where the RPM needle is dropping from 600 to 400 and stalled, and I always notice it happens when it was downshifted from 2nd to 1st and only happen at 1st gear when I put my foot on the brake while waiting at traffic light or waiting for traffic. And yet no fault code is showing up when I did a full scan using ODIS. Why didn't the car computer sense something is wrong and throw a fault code?

Could it also my car needs a software update? As my previous owner hasn't had his car service in Audi dealership, mainly independent service centre.

I guess I will have a couple of sleepless nights....
 

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#10 ·
We'll in my case it was nearly exactly same as yours, but in fact the car used to go into limp mode every now and again, but apart than that it was showing all sorts of fault codes, I replaced throttle body, gas pedal, air filters, maf sensor, it was fuckloads of things before I took it to a guy once it stalled and I couldn't even get it back on and after he looked at it he said it will be ecu, as it was showing faults all over the place and it wasn't even connected one to other, so new ecu that cost me something like £350 and it was good as new, but obviously you're not going into limp, no missfire etc. and obviously no codes whatsoever... As for the cables I would say disconnect them and tape them up so you're sure that they don't contact each other and don't have any influence on the issue. I would suggest to take it to a local garage that you can trust and ask them for an opinion, but obviously there aren't many like that...
 
#11 ·
Hi mate,

Sad to hear you've got this problem I've pretty much got the same problem, however I've got the 2 litre petrol. Whenever i stop at a red or at traffic or when I pull off my revs start normal then suddenly fall so the car goes and slows down. It's very annoying you must feel the same.

However now when I reverse or go into drive to pull away my car does it constantly and the revs fluctuate like mad I've uploaded a video onto youtube so you can see.

https://www.youtube.com/watch?v=Q-Y8jwFd6es

I'm trying to solve this problem as you are, hopefully we will find a fix ASAP!
 
#12 ·
Thanks for contributing your opinions and thoughts.

From I have gathered, most people who got this symptom have petrol version and not diesel and if it is petrol, it would be most probably due to dirty throttle body or faulty spark plug or bad idle control valve or even faulty ecu or vacuum leak or dirty MAF sensor. If it is faulty ecu, I heard that it would throw a fault code for sure, also it will be showing all sorts of lights on your dash, and big brake light will be flashing.

But mine is a diesel version and I can't seem to find anyone to have this symptom. But from what I have gathered, it could be due to bad EGR valve or bad ECU or low dual clutch gearbox oil (no one has mention the final drive oil?) or bad throttle valve (which I have already replaced).

Now I am hoping and waiting for some fault codes to show up so I know where to start from. The reason why I don't bring it to a mechanic is that I actually asked this question on justanswer.com and no one seem to have a clue so I guess it will just be wasting money going to see a mechanic.
 
#16 ·
I'd say tape them up yourself, they're not bad, can't see any problem you doing it. As for the car I can remember I was in exact same situation, so really sorry for you pal. Same as you I had done all of the same things, throttle body, cleans, sensors, have tried everything and fault codes were not completely pointing to an ecu, it was just loads of different stuff all over the place, but every time I would sort out the problem on the code another one would appear someplace else... I'd say get some prices together as I would imagine they will have to give you money back if it wouldn't be an ecu, obviously they need to replace it themselves rather than you coming down and pointing at it.
 
#15 ·
PS I would go to a good INDI and ask him to do the job. I bought the VCDS system and lent it to my INDI guy and he loves it and works better!!! Good luck
 
#17 ·
I had exact same issue, but mine in addition sometimes gave a "CLUNCK" when downshifting from 2. to 1. gear. so I went for a gearbox oil change and it solved my problem instantly.
 
#18 ·
Hi mate, when you said you have exactly the same issue, did you experience RPM dropping and sometimes lead to stalling when downshifting from 2 to 1? Just wondering if your car is manual or Stronic 7 speed diesel?

Also do you have your front & rear final drive oil change (in Volkswagen they are called "Haldex oil") or just gearbox oil change? When you have your gearbox oil change, do you have the oil filter changed as well or just the oil?

Thank you very much!
 
#19 ·
Hi mate

My car is an Audi A5 Sportback 3.0TDI Quattro with S-Tronic. (DPF OFF - EGR OFF)
It has gone approximately 150.000Km

Im trying to remember exactly because actually I did both following the same day:
1. Transmission oil change
2. A re-Remap because I got engine light on after a year of an old ECU Remap

I'll tell you what I exactly experienced.

In the start my car began to give hard "Clunk" when bringing the car to a complete stop (from 2. To 1.) In the meantime the RPM began dropping and stalling, not only when I did a complete stop but also when continued driving like 30-50 km/h, it didn't happen all time though but almost every day. Both faults happened almost in the same period of time. So I can't tell if it's two different faults or if it's one fault for both errors.

Check following Dropbox link for the a video of the error RPM drops and stalls:

https://www.dropbox.com/s/lummyfci4hw5ozc/Fil 19-06-2017 16.35.08.mov?dl=0

It did that for almost a week. I started contacting Audi and other transmission professionals, some said it's the mechatronic and others the transmission had to be refurbished! I didn't listen to them because I wasn't convinced about theirs troubleshooting.
So I thought to my self. why no go for a transmission fluid replacement with of course filter and gasket, so i did that. And I did the ECU remap again because of the engine light.
And it runs like a charm now. Haven't had any trouble since.

So I would advice you to hook up a VCDS and check for any errors to start with, VCDS and the one you tried.
Did you have an ECU Remap before?

Best regards
 
#20 ·
It did that for almost a week. I started contacting Audi and other transmission professionals, some said it's the mechatronic and others the transmission had to be refurbished! I didn't listen to them because I wasn't convinced about theirs troubleshooting.
So I thought to my self. why no go for a transmission fluid replacement with of course filter and gasket, so i did that. And I did the ECU remap again because of the engine light.
And it runs like a charm now. Haven't had any trouble since.

So I would advice you to hook up a VCDS and check for any errors to start with, VCDS and the one you tried.
Did you have an ECU Remap before?

Best regards
Hi Alaatt,

Good to hear that you got your issue fixed and saving yourself tons of $$$$$

So when you have your transmission oil change, did you refer to only the Dual Clutch Gearbox oil (7 litres of oil) or did you also
get the front & rear differential oil changed?

I do not have VCDS but I am using ODIS which the dealership here in Australia use and every time I scanned the system and checked for faults,
it does not come up with any fault. Unlike yours, you got engine light on which point you to some directions.

So did you remap the ECU yourself via VCDS? Is it hard to do? I am also planning to buy an aftermarket ECU from ebay and do a remap myself but
do not have any idea how to. Also I use ODIS not VCDS, so there might not be any instructions on the internet showing me how to do.

I found out the part number for the dual clutch gearbox oil for my car is G052529A2 however I can't seem to find the part number for the filter/gasket, not sure if
they are internal or external.

It seems to me that the clunk if you are getting is due to low dual clutch oil lever and the fluctuation of rpm is due to bad ecu remap (I could be wrong though).
 
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