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View Full Version : Weird Idle with Heat On



adam044
12-08-2014, 07:44 PM
It's gotten cold enough here to where I usually use the heat in the morning. Some mornings I tough it out to save some gas though. Today I noticed with the heat ON my RPMs bounce up and down when I'm stopped. It's very little (100 rpm maybe) but it's clear on the dash and you can hear the engine changing pitch. If I turn the heat off its fine. The vacuume on my boost gauge seems to stay the same whether the heat is on or off, I will double check that tomorrow though.

bhusted
12-08-2014, 08:08 PM
Using the climate control on these cars defaults to running the A/C to reduce condensation/humidity in the cabin. I bet what you are noticing is the A/C compressor cycling on and off and the engine adjusting to the load. The throttle body may need cleaning or alignment if the load adjustment is erratic. To test this theory try turning the heat on, but hitting the ECON button to disable the A/C.

adam044
12-09-2014, 02:07 AM
I will give that a try. I believe I have done that and it does the same thing though. I'll keep you updated.

SN95Audi87
12-09-2014, 11:10 AM
This happened to me too! I am glad I see a thread about it. The idle fluctuates between 50-100rpm. Its not a big deal but I always wondered. All my main vacuum hoses has been replaced as well.

adam044
12-11-2014, 03:54 PM
Still seems to do it with Econ on. Not as much though. It also seems to vary depending on outside temp, and how warmed up the car is. Hard to tell since I'm not at more than 1 or 2 complete stops to work.

Seerlah
12-11-2014, 03:56 PM
What is your coolant temp when you use the heat? Just wanting to know if your coolant is up to temp yet or not.

adam044
12-11-2014, 05:21 PM
What is your coolant temp when you use the heat? Just wanting to know if your coolant is up to temp yet or not.

Like I said above the rpm bouncing seems to vary depending on how warmed up the car is. I believe there is less bouncing when it is colder and not in the middle of the temp gauge.

pbcrazy
12-11-2014, 06:05 PM
Like I said above the rpm bouncing seems to vary depending on how warmed up the car is. I believe there is less bouncing when it is colder and not in the middle of the temp gauge.

When you turn on other power drawing options (heated seats, rear window defroster, etc.) do the rpms still bounce a bit? Or just when you turn on the blower?

adam044
12-11-2014, 06:50 PM
When you turn on other power drawing options (heated seats, rear window defroster, etc.) do the rpms still bounce a bit? Or just when you turn on the blower?

Heated seats do nothing. I use that almost everyday. I've never tried just the rear defrost. Who needs to see out the back window? I will test that tomorrow.

Maybe I should add when my window is closed and I pull the window switch to close (even when it's already closed) the engine will rev up slightly. Really weird I know.

pbcrazy
12-11-2014, 07:06 PM
It might just be the alternator kicking in, or a dying alternator. My guess is that since the car isn't completely warmed up, the engine is already working harder than normal and when the alternator kicks in it just stutters a bit. Just conjecture though, cleaning the throttle body/doing a TBA wouldn't hurt though

adam044
12-11-2014, 07:34 PM
It might just be the alternator kicking in, or a dying alternator. My guess is that since the car isn't completely warmed up, the engine is already working harder than normal and when the alternator kicks in it just stutters a bit. Just conjecture though, cleaning the throttle body/doing a TBA wouldn't hurt though

Or just don't use the heat... Throttle body looks easy enough to get to. What's TBA?

pbcrazy
12-12-2014, 03:44 AM
Throttle body alignment, if you have never done one it could very well be the problem. You will need full Vag-com or atleast the licensed version of VCDS

adam044
12-12-2014, 05:22 AM
Oh okay. I don't have access to VCDS. I have windows 8 loaded on my Mac and that's all I have access to for windows. I'm a Mac user.

pbcrazy
12-12-2014, 07:33 AM
Oh okay. I don't have access to VCDS. I have windows 8 loaded on my Mac and that's all I have access to for windows. I'm a Mac user.

As am I, and unfortunately you can't run VCDS with boot camp windows 8. You'll either have to buy a cheap windows laptop or if you have access to someone else's windows laptop (parent, significant other, etc.) just load it up on that. You'll need it, especially as you seem to be getting into modding a bit

adam044
12-12-2014, 08:59 AM
As am I, and unfortunately you can't run VCDS with boot camp windows 8. You'll either have to buy a cheap windows laptop or if you have access to someone else's windows laptop (parent, significant other, etc.) just load it up on that. You'll need it, especially as you seem to be getting into modding a bit

Not the first time I've been told that

pbcrazy
12-12-2014, 06:53 PM
Not the first time I've been told that

Use that $1000 to buy it. Best thing for your car