Intermittent high idle

[Simba2004]

Well, the fans are working nearly all the time but the speed increase happens only sometimes? It is not the case that I am using the fan and it is up, it is just the odd day it does that - it can be fine for 2 weeks and then do it all day one day and go back to normal the next day.

EssexGonzo, please don't scare me, something tells me that DPF works would be very costly... Something I want to avoid, especially in a new car!!

[EssexGonzo]

Well, the fans are working nearly all the time but the speed increase happens only sometimes? It is not the case that I am using the fan and it is up, it is just the odd day it does that - it can be fine for 2 weeks and then do it all day one day and go back to normal the next day.

EssexGonzo, please don't scare me, something tells me that DPF works would be very costly... Something I want to avoid, especially in a new car!!

If I understand it correctly, and there are many many others who know far more than me, some DPF equipped models are meant to do this if you haven't done enough longer journeys recently to get the exhaust up to a high temp to burn off the soot. I'm sure I experienced the high tickover occasionally in my old car but never had any DPF issues, so it's not necessarily a problem.

[Simba2004]

Oh right, I didn't get you at first there. Right, well that could be it I guess, it makes sense there. As long as it is nothing to worry about, I am happy!
The key point, take home message I think here is to bring it on a longer journey once in a while to clean the DPF and not use it on short journeys (like a run to the shop and back on a cold engine!)

[Maccarone88]

Hi! i have an Audi A3 from built in Jan 2007 engine code BMN 170bhp SE TDI version.
i've noticed my car does the same issue. i had the car for 8 months.
i start the car and is around 850/900 rpm once all settle is 800rpm.
once i start to drive the car after 4/5 minutes the car start to over revving from the usual 800rpm to 1000/1050rpm.
it has never done it before (i bought the car back in december 2016) and now we are in Summer 2017.
all my friend audi's are going just fine at 800rpm once the temperature is spot on 90degrees.
it would make sense if yes i make short journeys in town and the car won't like it much but the truth is i am constantly on the motorway on 6th gear
driving my car at 70mph and exceeding it where i can.
so ir really doesn't make sense where the car is driven in motorway or town the rpm should stick at 800rpm winter or summer too.
have you noticed any change from winter to summer? is there any other member which could give me a more accurate explanation looking after the fact the car is driven both motorways and town and so that the town driving couldn't be the issue?
i replaced:
Solenoid pressure boost.
Temp sensor (brand one)
cleaned: EGR , throttle body.
Tested: Fan Voltage need , Alternator Voltage (13.10V so plenty to supply for all the extra accessories in the car)
oil pressure all good. i change oil every 6k and not 9k as the car ask me to do on the dashboard.
Anything else i might need to know why this happen? any updates would be really appreciated i don't think is an healthy thing running the car at 1000rpm as the clutch yes is to be used on the motorway and sometimes we press it whilst at higher rpm but when on idle and on traffic i don't think is built to get that amount of stress (and i don't like to ride the clutch on gear in traffic) so i leave in neutral when i have to stop.
thank you in advance for any update.

[Rob69]

Get it scanned for fault codes before changing any more parts

[Maccarone88]

Hi , thank you for the response.
i've scanned the car on a VAGCOM it only give me Stereo related code as its an aftermarket one.
then it give a 00361 which is related to heater element for auxiliary heater (could that be part of the problem?)
Also i was reading a lot thru the common blogs online and here Re increased idle - Audi Q3 Forums - Page 1 the car was presenting the same issue. i used not really pay much attention to my car temperature on how long it took to go to 90degrees but i've noticed sometimes it take quite a while and it can be related to a faulty Coolant Thermostat and i am really curious to change it usually doesn't bring a fault code.
any advice is always welcome and would help a lot on what to do.
thank you

[Rob69]

That Q3 article is on about a 2013 common rail engine with DPF, I think your will be a PD without DPF ? If it takes a long time to come up to 90'C and you notice the temperature dropping off if your are coasting down a hill or turn the heating up, then your thermostat is needing changing. My 1.9 tdi was sluggish to heat up and a new stat lets it come up to full heat in around 5 minutes or 2 or 3 miles of driving. I don't think the heater element code is causing the high idle 00361 - Ross-Tech Wiki
I've heard that a poorly performing alternator can cause the revs to increase to try and raise voltage, can you check the voltage output with a meter? Yours looks low at 13V It should be around 14 to 14.5 v running.

[alankru]

Hi , thank you for the response.
i've scanned the car on a VAGCOM it only give me Stereo related code as its an aftermarket one.
then it give a 00361 which is related to heater element for auxiliary heater (could that be part of the problem?)
Also i was reading a lot thru the common blogs online and here Re increased idle - Audi Q3 Forums - Page 1 the car was presenting the same issue. i used not really pay much attention to my car temperature on how long it took to go to 90degrees but i've noticed sometimes it take quite a while and it can be related to a faulty Coolant Thermostat and i am really curious to change it usually doesn't bring a fault code.
any advice is always welcome and would help a lot on what to do.
thank you

I don't think that would be the cause of what you are witnessing. With my first A3 (the one I had at the time of originally posting in this thread) I subsequently discovered it had the same fault code for the aux heater; I understand that it just means that in the Winter you won't get hot air out of the cabin air vents until the engine is warm. The auxiliary heater is fitted so that in the winter you can get hot air through the air vents quickly, as the diesel engine takes a while to warm up. Hope that makes sense?
Reading back through this thread, it was thought that the cause of the increased revs in Winter was the load from the aux heater...I didn't know at the time of my original post that it wasn't working anyway.

However:
My subsequent A3s have all done the same thing; idle revs increase on cold winter days.
My subsequent A3s also have increased idle revs when the car has been sitting a while.
This is when you first start the car - after a few minutes, things settle.

As you have explained, neither of these circumstances apply to you as you are experiencing increased revs after a number minutes.
With my 1.9tdi, I had heating up issues when the dealership left air in the coolant system. It worked its way out in the end and I topped up the coolant - it was then back to normal.

[Maccarone88]

Hi thank you again to take time and respond.

i understand that maybe that idle issue would have happened when the aux heater was not installed in certain models.
And i do get why it could have happened in the winter time in order to compensate cold outside temperature , slightly revving in order to warm up.
but why am i experiencing it in full summer time when outside is 20 plus degrees and is so random?
i mean traveling sometimes is all full at 1k rpm for the whole journey then other times same journey kinda quiet and showing it 2 on some motorway slip road/roundabout.
then if i turn it off and leave for a red light length of time and turn it on the car is on idle at 800rpm then 5 minutes gone back to 1000/1050rpm.
i don't think it should happen that's all at least no in the summer time.
thank you again.

[Maccarone88]

Hi thank you for the response.
my car is a BMN 170 bhp - bigger turbo and Siemens VDO Piezo Injector engines with DPF-- Read more at: ht - (c) TorqueCars
https://www.torquecars.com/volkswagen/2-0-tdi-140-170-tuning.php
this is the link with engine codes. mIne is the BMN 17obhp with DPF so i thought it may have been almost same specs on that point of view.
the car doesn't go down on temp if i am resting but it take a awful lot of time to get there even driving and sometimes fairly normal.
the garage mentioned that 13.10v on alternator is plenty enough but i didn't know it should have been 14/14.5v but they said on resting just on idle it was at 13.10
that might increase if the car is running. but i'll still mention it.
i guess is only a matter or power of deduction at this point. one by one the issue will come up and i'll keep everybody posted.
i still believe an audi once warm should not exceed 900rpm at idle and that is a fault and not a feature as mentioned in some other forum online.
thank you again. and another question would be: would the DPF play a role in with this issue? and how?