Intermittent high idle

[Maccarone88]

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.

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 , i've inboxed you let me know if you have my msg. thanks

[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?

Hello everyone. i hope you had a nice week after bank holiday week end.
as i stated i would have made and update of what is the cause of the issue. (potentially)

After Throttle body/EGR manual clean.
Carbon clean the whole system
changed solenoid pressure release valve (wich will need to go back at eurocarparts westwood cross becaue it cost 66gbp and i want them back as it failed)
Run VAGCOM 2 times and only showed error 00361 (aux heater element)

My conclusion is.
The aux heater completely failed and was on even when running on cold air. it was running yes but not producing hot air as the element was burnt out and somehow it was sucking electricity.
after that i discovered one of the radiator fan (driver side) failed so i replaced myself fro 62gpb
The battery was yes making the car start but it was knackered by this little things and time
So the problem was the car going from 800rpm to 1050rpm on idle , if you pay close attention the car only does that when the fans comes on.
meaning the battery is holding enough charge to make the car start petrol/diesel don't matter. once the car start and everything is running
the voltage produced is not enough to occasionally support both fans so the car start to rev up instead of taking electricity from the battery as there is some amperage there but again not enough so it rev up and compensate the lack of electricity by taking it from the alternator.

MY advice: anyone who has a TDI audi anything higher then 80kmiles just go with a mate battery and watch the car behaviour sometime the obvious answer is right there and we think is more complicated then what it is.
replacing EGR Throttle body is around 500gpb from a garage probably 250gpb if you do it yourself , replacing the fan 62gbp but a garage qould quote around 200gpb all this little things sum up so check fan first if they ran and car does that then is the battery.
hope this was useful to someone as it was for me.
thank you all

[Maccarone88]

I've noticed lately that sometimes the idle speed is higher than it should be - just over 1000rpm, instead of the usual 800-900.

I initially though it might have been the choke (or equiv.) but it happened yesterday when the engine was fully warm, so it can't be that.

When it happens if I turn the engine off and back on again it reverts to the normal idle speed.

The car is a 54 plate A3 Sportback 2.0TDI 140PS BKD.

Any ideas what might be the problem?

Cheers

Please read the last comment on that link it might help you out. cheers.
Intermittent high idle - Page 3