RPM occasionally fluctuates with AC Compressor on

[Andratch]

well, i dont think it has an impact at all, since i usually keep the gas pressed at stop lights to 1000 rpm anyway to avoid my car shaking back and forth

Interestingly, I use my foot to keep my rpm at 1k rpm to make the surge go away....so this may be on to something! I'll give this a shot.

[Sylverlee]

no, i was doing this previously to avoid the issue described in this thread, rpm going up and down, shaking was not a good way to describe it

Interesting. I get mild vibrations every 13-15 seconds or so.. It varies depending on the day, sometimes it can barely be felt but sometimes like 300rpm.

[inlinesix123]

Sylverlee
Andratch
When i would stop at a light, my RPM would sometimes dance back and forth between like 700 and 900ish if i were to guess. I would just keep my gas pedal pressed to around 1000 RPM while stopped to make this go away since it annoyed me. It only happened with AC on i believe, it almost felt like there was a vacuum leak.

[Sylverlee]

Sylverlee
Andratch
When i would stop at a light, my RPM would sometimes dance back and forth between like 700 and 900ish if i were to guess. I would just keep my gas pedal pressed to around 1000 RPM while stopped to make this go away since it annoyed me. It only happened with AC on i believe, it almost felt like there was a vacuum leak.

Yessssss finally fixed. This made me super happy. I was thinking of all sorts of fixes like AC recharge, new condenser etc. Funny that this was able to fix it so easily. So smooth now.

[inlinesix123]

Yessssss finally fixed. This made me super happy. I was thinking of all sorts of fixes like AC recharge, new condenser etc. Funny that this was able to fix it so easily. So smooth now.

Congratulations Glad I could help

[Andratch]

Sylverlee - how did you pull the BIN file?

[Notan_S54]

I have a question related to the topic. Does anybody else’s car RPM drop drastically slower like the throttle is being slightly held with ac on? My car will have the longest rev hang with ac on vs when off?

[Andratch]

Reflashed to 950 rpm today, and the idle fluctuation is totally gone! I may try 900 to see if that works too.

[Sylverlee]

Reflashed to 950 rpm today, and the idle fluctuation is totally gone! I may try 900 to see if that works too.

Nice! Curious if 900 works..

[Andratch]

Hey folks, unfortunately I have to report back that this problem was NOT solved by adjusting the idle rpm.

My idle fluctuation is quite bad now, dropping down to about 500 rpm and then up to 1200, always happens with the AC on but sometimes with it off. I am changing the idle control valve (ICV) this week to see if that helps. Mine was not clogged, but perhaps it was definitely original, so perhaps it was not functioning properly. The next step would be looking for a vacuum leak.

As a reminder, I do have a Turner CSL intake with a MAP sensor. I'm curious if that is a factor somehow. Those of you with this problem, are you using a CSL intake? Are you alpha-n or map?

[Andratch]

Quick update -

I took the Turner box off and started the car with no intake on. It ran smoothly for about 2 minutes with the AC on, then started to fluctuate.

I unplugged the idle control valve (which is clearly functioning fine), and the fluctuations immediately smoothed out. Plugged it back in and they slowly started again. Then I left it unplugged for longer, and the car started trying to compensate for fluctuations with the throttle.

I am not really sure what to do with this data, but it seems to me like a vacuum leak wouldn’t be the problem if it’s happening without the intake on.

I’m going to call Kassel on Monday to see what they say.

https://youtu.be/yvcfLyjeaJ8?si=MgpH4Tf_kJUM7o_w

[heinzboehmer]

QI am not really sure what to do with this data, but it seems to me like a vacuum leak wouldn’t be the problem if it’s happening without the intake on.

ITBs means no vacuum in the plenum. All vacuum is in the vacuum rail (and the connected hoses) right above the throttle bodies. So don't rule that out just yet.

What tune is on the car? Could also be related to that.

[Andratch]

ITBs means no vacuum in the plenum. All vacuum is in the vacuum rail (and the connected hoses) right above the throttle bodies. So don't rule that out just yet.

What tune is on the car? Could also be related to that.

Oh interesting, so if I was to do a smoke test, I could just hook it up to the ICV inlet hose?

tune is a standard Kassel CSL tune.

[Andratch]

Quick update,

ran a smoke test via the idle control valve hookup,

confirmed that burning baby oil smells bad, and that I have no vacuum leaks.

[Andratch]

Another Update -

I chatted with Kassel tech support on the phone this morning. They say they've seen this before on some CSL intake conversions - and are going to do some monitoring and tweaks via remote desktop to my laptop connected to OBDII. That will probably happen on Wednesday, because I have to put the intake back on first. I'll post back with what we find.