Audi A4 cold idle.

demanufactured

Anyone who owns a 1.9 tdi ever notice the idle speed changing every 10 seconds or so when cold.
Have noticed the lights dipping slightly when it happens too.
You can hear sonething switching from inside the car when it happens

My old passat did the same thing

Here's a video I took... You can hear the idle speed dropping for a few seconds s then coming back up again.
Don't thinks it's a problem.. But would like to k of what it is.

http://youtu.be/M42ps62rHcs

kildarelad

Clean your EGR it may be slightly blocked will show when its cold

tonneman72

It sounds like the glow plug controller activating the afterglow of the glow plugs thus explaining the clicking inside car and dimming off lights

demanufactured

kildarelad wrote: »

Clean your EGR it may be slightly blocked will show when its cold

Brand new egr

demanufactured

tonneman72 wrote: »

It sounds like the glow plug controller activating the afterglow of the glow plugs thus explaining the clicking inside car and dimming off lights

Assuming this is done to help on very cold starts... Glow plug light goes out after about a second when ignition is turned on.... Engine always starts on first go.

gctest50

demanufactured wrote: »

Assuming this is done to help on very cold starts... Glow plug light goes out after about a second when ignition is turned on.... Engine always starts on first go.

the afterglow is done on some engines to reduce smoke on startup - makes a good difference, you'd see it if you disconnect it



it may not bring on the glow-plug-light because some people would bring the yoke back to the garage and whine if they saw the light on when the engine was running

spiel from NGK

After-glow takes place after ignition when the engine is running - i.e. during the first few meters travelled by the car.

It is required to prevent heat loss whilst the engine is warming up to its optimal operating temperature.
Without it, there would be a considerable amount of toxic emissions and white and blue smoke from the exhaust. The engine would
not run smoothly either, displaying the characteristic cold-start knocking.

http://www.ngk.de/fileadmin/Dokumente/EN/Brosch%C3%BCren/ngk_glow_plugs_faq_en.pdf

dieselbug

What year is the car and what is the engine code.

demanufactured

dieselbug wrote: »

What year is the car and what is the engine code.

2004 audi a4 b6
Not sure if engine code.

tossy

It's running in cold start mode i.e the ECU thinks it's a lot colder out than it is due to what it thinks the coolant temp is, i'd say if you got it scanned you will find a fault for a coolant temp sensor.