idle drop when a/c is off?

[sloweryucf]

Idle drops to 800 rpm and it's rough. What the hell is that about?

[Audi Skate Snow]

when you turn the AC on the computer compensates by raising the engine RPM because the AC puts a load on the engine. so when you turn your AC off its prolly adjusting and drops back down.

[dirtybrd]

With a combination of possible bad motor mounts.

[Audi Skate Snow]

With a combination of possible bad motor mounts.

ahah true. that could be that "rough" feelin hes getting

[dirtybrd]

You should caught right on to that Audi tech.

[Audi Skate Snow]

You should caught right on to that Audi tech.

smart ass... i actually just read it reeal quick and saw that he asked about rpms droping.... dint catch the rough at first

hey how is your car running BTW? any #'s or anyhting?

[dirtybrd]

Runs great, no #'s. I haven't driven it since mid Oct. I think the gas has gone bad in it.

[Audi Skate Snow]

Runs great, no #'s. I haven't driven it since mid Oct. I think the gas has gone bad in it.

ahah.. why havnt you driven it?

im hoping by end of the month my car will be done. I ended up changing the setup that im doing.

[dirtybrd]

I drive my Honda everyday, 130 miles a day and 35mpg. I leave the house at 5:30am and get home around 7pm. Between spending time with my lil girl and taking care of things around the house on the weekends, I just haven't had the time.

[Audi Skate Snow]

I drive my Honda everyday, 130 miles a day and 35mpg. I leave the house at 5:30am and get home around 7pm. Between spending time with my lil girl and taking care of things around the house on the weekends, I just haven't had the time.

damn. sounds like my life right now. minus the drive to work. thank god i work 1 mile away from where i live.

anywho sorry for the thread jack.

[dirtybrd]

That how it used to be. I can almost see my old job from the house. But there I wasn't bringing home $1200 a week

[sloweryucf]

With a combination of possible bad motor mounts.

Brand new motor mounts unfortunately. I thought it was that as well.

[dirtybrd]

Misadjusted snub?

[Audi Skate Snow]

Brand new motor mounts unfortunately. I thought it was that as well.

is it a shake or like a rough idle because the RPMs drop low and come back up ?

[sloweryucf]

Misadjusted snub?

They (dealership) did put a new OEM snub mount in. Perhaps I should try and recenter it. Thing is that I don't remember the RPM fluctuation on the dash.

[sloweryucf]

is it a shake or like a rough idle because the RPMs drop low and come back up ?

Not a shake, rough idle. The RPMs drop and stay down when the a/c is off. When the a/c is on, sometimes the RPMs drop and then come back up.

I also thought there might be a vaccum leak but dealership said no leaks. Not sure how the a/c system works with the engine to be honest with you.

[Audi Skate Snow]

ok so are your RPMS droping really low when you turn it off

[diagnosticator]

The idle speed differential that you noticed, is due to the programming of the ECU. My '03 used to do this also, until the ECU was reflashed to the '04 "AK" suffix software version. The "AK" software has this idle speed offset corrected, and it does not occur now. Your ECU can be updated with the "AK" version by the dealer.

[pa4ul]

my car does the same thing. When the AC is on the car dosent studdered but once the ac goes of it seems like it has alot of trouble stayin on. It has even turned off on me before. Is there an idle adjustment maybe>? help.

[sloweryucf]

The idle speed differential that you noticed, is due to the programming of the ECU. My '03 used to do this also, until the ECU was reflashed to the '04 "AK" suffix software version. The "AK" software has this idle speed offset corrected, and it does not occur now. Your ECU can be updated with the "AK" version by the dealer.

How much does that run?

[diagnosticator]

The ECU software reprogramming to PN suffix "AK" version will eliminate the idle speed difference with the A/C ON and OFF. Another way is to use VAG-COM/VCDS to adjust the idle speed in ECU adaptation channel 001. However, the idle adaptation channel is directly adjustable only for ECU versions up to "AF". For ECUs after "AF", IE "AK" >, the adaptation channels are locked against direct change, so Lemmiwinks or similar is needed to access the idle speed adaptation channel, but since the idle speed offset with A/C mode is not an issue for versions "AK">, the adaptation channel lock out isn't really an issue anyway.

[diagnosticator]

How much does that run?

Dunno, probably the minimum shop labor time, at least. The software update is documented in the TSBs, specifically to address a cold start misfire problem. The reflash update is the '04 "AK" ECU PN suffix after the reprogramming is performed.

The TSB says to perform the update only with the customer's complaints of cold start misfire, for warranty. If a paid job, then jusk asking to have the update flashed should be the only requirment.