Air conditioner on = throttle lag. Air conditioner off = no issues. Thoughts?

[Highlander1010]

UPDATED

Moving the original thread down a bit.

The issue was with 2 O Rings in the air conditioning system being broken. They were causing a slight leak on a vacuum line, which both lost coolant and A/C low temp for me and robbed the car of vacuum in 1st gear/low RPMs.

Something to look out for in the future if you lose boost and A/C at the same time. It was so simple there was no way I was going to find it, but my Audi Dealer (Barrier - Bellevue, WA) did and got me all fixed up. I hammered the pedal with full A/C on from a dead stop today and not only was the issue gone, but I had more powerthan before. Since this happened around the same time my K04 went in, I may have never actually experienced the full power of the new system until now.

Pretty good day all in all.


Original Message

Hi All,

For some following, you'll know that since my K04 went in I've had some weird pedal/throttle lag at low speed (parking lot, stop sign/light) around 800 RPMs. The way this presents is when I start to drive from a stop or at a low parking lot speed, and I push the gas pedal, I go from a smooth 800 RPM idle to RPMs bouncing from 800 to 300 and no get up and go for a few seconds. It doesn't make sense that it would be the turbo since it happens well before the turbo is even involved in the get up and go process. Still, the timing is the same as when it went in.

Today, for the first time, I turned off my AC on a drive since the weather was so nice out. I parked outside for a bit and when I came back my car was really hot. I was about to get a car wash, so I turned on the AC while I read email on my phone to get the car cooled down. Weird thing was, the AC wouldn't cool even on Lo for driver and passenger. I thought it odd and backed out of my parking space. Then I flipped into "S" and BOOM...throttle lag.

Then I got a bright idea and immediately switched off my AC and the lag was IMMEDIATELY GONE. I put it on again and the lag was back. I got my car wash and tried this a few more times on the way home. Sure enough, I could flip on the AC and cause the lag and flip it off and stop it.

So, here's the million dollar question. What connects the AC and Throttle or Throttle response together in some way? Sensor(s)? Motor or Pump? Belt? Other? If someone knows I'd be extremely grateful and I want to kill this problem and get my car back to 100%. I wonder if something were dinged, damaged or marginally connected when my new turbo went in.

[Tanzimur]

You have got to be kidding me..... a/c equals an accesory that takes up more power to run itself from the already there engine power so when turned on.... i think you get what im getting at from there...

[shonseb]

Yup, A/C is an accessory that gets it's power directly from the engine. It is run through the pulley system that also controls your power steering, alternator, etc. When you turn your ac on it will rob your car of power, causing it to feel sluggish. When idling, your ac will work but not that great. When you start driving you are increasing the engine rpms, and essentially increasing the amount of power that your ac gets, allowing it to cool your car much faster. The EC pulley, or any light weight pulley for that matter, is designed to take some of that 'accessory' load off the engine, thereby increasing performance.

[gdawg'05a4]

Yes, the A/C does rob some power but it should not to the point of what Highlander is describing. Though I don't have a K04, I've never experienced anything like that (excessive lag and bouncing RPMs taking off or throttle modulation at low speeds) with Stage II and I have the A/C on 99% of the time. For the times I turn the A/C off, I don't notice much, if any, in throttle lag when taking off from a stop or at parking lot speeds. To me, it sounds like something else is going on.

[WAF]

ill check it out i've only used my A/C once or twice this year. But never notice a difference other than a small amount of beetle juice i takes run it. Not throttle lag, but feels a lil slower which is normal. Do you have any surging?

[b6onboost]

The AC pulley is sapping a very small % of engine power. The throttle should respond the same, the turbo spool/lag identical, you just may notice the car is a tad slower..but its basically negligible.

Your off-idle throttle issue is a problem. You shouldn't be dropping below idle or seeing rpms bouncing around (surging). That's the K04 install, tune, or a sensor problem. And my best guess is whatever is causing that is related to your AC lag problem too.

[WAF]

x2 IMO

[Highlander1010]

The AC pulley is sapping a very small % of engine power. The throttle should respond the same, the turbo spool/lag identical, you just may notice the car is a tad slower..but its basically negligible.

Your off-idle throttle issue is a problem. You shouldn't be dropping below idle or seeing rpms bouncing around (surging). That's the K04 install, tune, or a sensor problem. And my best guess is whatever is causing that is related to your AC lag problem too.

Yes - and that is what I am talking about. I am still thinking sensor at this point, but none scan poorly. We'll see.

To the rest above - DUH! Thanks

[WAF]

DUH no problem

[BIG_ROOSTER]

Something to consider had an excursion that the a/c clutch wouldn't engage. Turns out a bad coil pack was shorting the same ground on the ECU that the clutch used. May look into an ECU issue.

[shonseb]

DUH no problem

x2 lol

[dscline]

Have you checked your logs for any misfires? I've been following threads on the VW boards, as I'm planning on upgrading my turbo in the coming months. Their engines are very similar, and there's a lot of traffic on those boards, so I've been monitoring as much info on the options as I can find. There are a lot of people on the VW boards complaining of various issues with APR's K04 tune, including surging, and misfires at idle. Here's one example. No reason I can think of for it to be related to AC, but just throwing it out there. APR is supposedly working on a "v3" tune that hopefully improves these issues, though from what I've read, they've never officially acknowledged them.

[van462]

Curious, if you unplugged the connector to the compressor so that the pulley clutch won't engage, and see what it does. I would think the idle up command would still be given. That way ecu might see the a/c on but you wouldn't have any extra engine load. Might generate a hidden code when the a/c high pressure side never sees a pressure build. But you can clear that. I looked from the topside of the engine bay and i didn't see the connector, may have to pull the belly pans to get to it. Just wondering if the a/c compressor is on its way out and is putting much more load than it should.

[buelldozer]

Curious, if you unplugged the connector to the compressor so that the pulley clutch won't engage, and see what it does. I would think the idle up command would still be given. That way ecu might see the a/c on but you wouldn't have any extra engine load. Might generate a hidden code when the a/c high pressure side never sees a pressure build. But you can clear that. I looked from the topside of the engine bay and i didn't see the connector, may have to pull the belly pans to get to it. Just wondering if the a/c compressor is on its way out and is putting much more load than it should.

I'm troubleshooting my own A/C issues right now (Implausible Signal + Intermittent Circuit on N280, A/C will only blow hot air) and I can tell you that you WILL have to pull the belly pan. No way to access that connector from the top. Lord knows I tried last night and I've got the cuts and bruises all up and down my right arm to prove it.

[buelldozer]

Something to consider had an excursion that the a/c clutch wouldn't engage. Turns out a bad coil pack was shorting the same ground on the ECU that the clutch used. May look into an ECU issue.

The A/C compressor doesn't have a a clutch in these cars. The compressor is spinning full time but it's only working when the N280 A/C Compressor Regulator Valve tells it too. Basically the more cold air the HVAC system calls for the more refrigerant the N280 has the compressor...compress so it can supply colder air at higher volumes.

[Highlander1010]

The A/C compressor doesn't have a a clutch in these cars. The compressor is spinning full time but it's only working when the N280 A/C Compressor Regulator Valve tells it too. Basically the more cold air the HVAC system calls for the more refrigerant the N280 has the compressor...compress so it can supply colder air at higher volumes.

Find any commonalities to throttle response yet?

[Highlander1010]

Updated with conclusion at top. Good for folks to be aware of.

[knucklehaedjcz]

I wonder if this could be my issue. I noticed a few weeks ago that the ac seemed to not be as cold as it used to be. Also, for example, I am going over a speed bump, I slow down and then after the bump when I accelerate, I press the gas pedal and nothing happens for a second or so, then it goes as normal. I've also noticed a slight coolant smell a few times. I had the car in for 25k service a few weeks ago before I noticed anything other than the coolant smell. They pressurized the cooling system and found no leaks although the coolant was a bit low. Do you think this could be the same issue Highlander?

[Alex1188]

Were are these o rings located?? I have noticed when i turn on my ac my vaccum will go from -21 to -16, could these orings you speak of do this, i also will have a slight delay in boost as well...

[Highlander1010]

I wonder if this could be my issue. I noticed a few weeks ago that the ac seemed to not be as cold as it used to be. Also, for example, I am going over a speed bump, I slow down and then after the bump when I accelerate, I press the gas pedal and nothing happens for a second or so, then it goes as normal. I've also noticed a slight coolant smell a few times. I had the car in for 25k service a few weeks ago before I noticed anything other than the coolant smell. They pressurized the cooling system and found no leaks although the coolant was a bit low. Do you think this could be the same issue Highlander?

Sounds like it. I would have it checked out again if that is happening, especially after a service.

Were are these o rings located?? I have noticed when i turn on my ac my vacuum will go from -21 to -16, could these o-rings you speak of do this, i also will have a slight delay in boost as well...

I didn't get the exact location, but I can ask them for it.

[Highlander1010]

Answer as to where is "at the schrader valve."

[Alex1188]

Answer as to where is "at the schrader valve."

Really?! at the schrader valve...hmmm...that shocking, i dont even see why that would happen unless it was tampered with to fill or release pressure from the system...CRAZY!

[Highlander1010]

Really?! at the schrader valve...hmmm...that shocking, i dont even see why that would happen unless it was tampered with to fill or release pressure from the system...CRAZY!

I need to open the manual and go learn more about it. It was coincidental with my K04 install, so I wonder if it was possibly damaged then, but I don't know the physical relationship or proximity.

[Alex1188]

Schrader valve is the fill valve on the lines that run to and from the ac unit, looks like an over sized valve stem on a tire, the schrader valve is the valve inside the stem. There are schrader valves on your rims, they are what keep the air or pressure of what ever is in the system, kept in side the system.



Actual Schrader Valve