My quick guess is knock. What kind of car you have? If its a 1g, get a pocketlogger.

ok when i turn my A/C on my rpm goes from 900 to 100 then dies when i put a turn signle on. My friend said its the ICS and im starting to think hes right because my Idle Surge is still here...

just looking for some openions

THX

I would do a boost/vac leak test before deciding to replace the ISC.

What other symptoms do you see? Any engine codes?

Its possible that if everything is acting up when you start turning more stuff on it might be that the alternator isnt keeping up and is going bad.

Did this just start one day? If your battery died, your ecu might have reset.

well i know i have a big leak in my intercooler i just havent found a replacement one yet, and yes i have a CEL but i havent gotten it checked yet.

I would think it is your ISC. When the load on the motor changed, the ecu signals the isc to open up to increase the idle rpm. Sounds like your isn't doing that.

I can run faster than my car can go with the A/C on.
I bog at stop lights, and geo's pull lengths on me when trying to tear out of a sticky traffic situation in first gear.

So the problem is a severe loss of power even when WOT in first gear. Anyone else have such issues when using the A/C?

The A/C condensor should not use that much power. Its been a while since I have run with A/C but my car would still get up and go, but it was a noticeable difference. When the A/C if off does the problem totally go away, because the A/C could be just exhaggerating another problem?

Usually thats a sign the ac compressor is goin south. Does the a/c make any noise when you first turn it on for the day?

twinturbo3k said:

The A/C condensor should not use that much power. Its been a while since I have run with A/C but my car would still get up and go, but it was a noticeable difference. When the A/C if off does the problem totally go away, because the A/C could be just exhaggerating another problem?

Click to expand...

I like the way you think.
I agree obviously there will be a power hit but I definitely think there is something else going on. It was quite hot out there day, but I wasn't driving the piss out of the car anyhow (heatsoak?).
The problem is 90% gone with A/C off. The car will be fine though most of the time but once in a while I will see a loss of power when getting into boost. I'm getting negative timing with the onset of boost and this is technically (along with drag from accessories such as A/C) what is causing the massive power loss.
But I can't see why the car gets lame when when I first hit boost and why it only happens sometimes.

Maybe its phantom knock, exacerbated by hot temperatures and having the A/C on?

The fuel is surely there, the stock pump is rewired and this is in the 2k-4k rpm range so itd be tough to be running too lean (real knock).

ekanddsm said:

Usually thats a sign the ac compressor is goin south. Does the a/c make any noise when you first turn it on for the day?

Click to expand...

The A/C makes almost no noise, other than a slight hiss when coming online that I've noticed in many other cars. I'm sure its normal.
The A/C does smell though, it doesn't stink but it has a cold (go figure), odor that may indicate it needs to be recharged or serviced?

Thanks for your contributions guys.

I'm experiencing MASSIVE power loss and lack of responsiveness from the engine when running the A/C. If the A/C is on, I have to floor the throttle from a stop in order to get power -- it's like using 4th gear on a manual tranny from a stop light. If I turn A/C off while giving throttle the power comes back immediately like normal. This isn't normal A/C load on the engine, this feels like I'm towing a boat or something! I don't get it.

I'm very certain this has something to do with my recent mods I performed on my car's cooling system where I reassigned my fan control to a fan controller (cut the stock fan wiring) so I can run 180-190 temps in 100 degree weather. Ever since I performed this mod my A/C seems to put a huge load on the engine. At times it can force my car to stall out. DSMlink is set at 950 idle.

I'm hoping that someone familiar with how the A/C system works relative to load on the engine can explain what could cause sudden massive engine load only when the A/C compressor is turned on? I read Luv2Rallye's posts here and I think this may be on the right track...something about fan wiring activating the compressor, etc... http://www.dsmtuners.com/forums/showthread.php?t=254447

Any ideas? This makes no sense to me.

Since my post was moved here and there is no solution yet, I'd like to add some thoughts on the suggestions brought above...

1. I have a new ISC so I don't think that is the problem. This isn't caused by low rpms.
2. I have a new 165A alternator and an almost new optima yellow top. My system reads 13.5 to 13.8v so low voltage shouldn't be an issue.
3. boost leak does not make sense -- this problem goes away as soon as you turn off the a/c
4. No CELs.
5. In MY case this occured right after my fan controller / cooling system mod. I'm guessing it has something to do with the fan wiring harnesses I cut and don't use anymore.

Can someone explain how the a/c works, from when you turn on the switch and how it signals everything to run?

I'm also looking for the same information.
However, I have not done any cooling mods like Rice Over Wheat or anything of the like, but when A/C is on its like starting in 4th gear. The moment I turn the A/C off I am back to full power.

Rice Over Wheat, perhaps your issue is not related to your recent mods?
Just somehting to think about.

Do compressors ever seize up making the load they put on the engine much higher than they should?

Big cams (272e/i) low vacuum to start with + high crank draws (Ac+165 amp alt. under load)= Fall flat on face.

You have to choose a smaller intake cam (less rump rump) or no AC (swelter is summer)

Not being a a$$ but take your pick.

Since this problem surfaced only recently, months after I've been driving on 272s and my new alt, I don't believe that's my problem. Maybe if you can explain in more detail why you think that's the case, particularly high crank draws and a/c operation. I run high idle in order to keep my vacuum healthy anyway (-15hg).

CB, it may not be related to all my cooling mods but this happened only afterwards so I was first looking for an obvious cause/effect. When did you start getting the same problem?

Based on Luv2Rallye's post I linked earlier, I'm gathering that when the compressor is turned on the ecu sends a signal to the a/c fan to activate. These are now open wires on my car and I'm wondering if there's some kind of feedback signal that the a/c system requires and isn't getting anymore. I'm just not familiar enough with how the a/c system works on a dsm...electronically that is. I might just pull the stock fan relays/fuses since they aren't used for anything anymore and see what that does.

ekanddsm said:

Usually thats a sign the ac compressor is goin south. Does the a/c make any noise when you first turn it on for the day?

Click to expand...

It just started chirping (much like a bird) whenever the compressor engages. So thats when I turn it on and when the ECU is autonomously turning the compressor on and off during operation.

PieEyedPiper said:

I can run faster than my car can go with the A/C on.
I bog at stop lights, and geo's pull lengths on me when trying to tear out of a sticky traffic situation in first gear.

So the problem is a severe loss of power even when WOT in first gear. Anyone else have such issues when using the A/C?

Click to expand...

I had a similar problem when i turned the AC on, it would almost fall on its face especially when on the brake. For some reason I tested the coils in the ISC and sure enough it was bad. So I purchased a new one and now the car runs like a car should with the AC on. Just throwing it up there, I dont know exactly whats going on with your car, but it sounded sorta similar to mine. I'm sorry if this was absolutely no help.

Jason

Nothing to do with ISC in my case. My ISC is the brand new black one from DSMISC.com. Idle rock solid.

Ok, after monitoring this problem some more I have connected the problem to a large dip in voltage when the a/c is turned on... -1 volt to be exact. What I suspect is when my voltage plunges my fuel pump has its output weakened.

Thing is, my fans are not connected to stock wiring so the activation of a/c fan isn't the draw. I thought the compressor is belt driven so I don't see why that would be drawing all this additional voltage.

What I want to do is remove the signals to activate the fans. There are two relays in the engine bay fuse box, lower right corner: "COND. FAN (HI) VENT.COND" and "COND.FAN (LO) VENT.COND.". Anyone know if these things can be pulled if you no longer have the stock fan wiring? I don't think I need the associated 30A and 20A fuses either come to think of it.

I figured out the problem...the a/c condensor pulls over 1v from the alternator's output at equal rpms. When the a/c belt activates it slows the alternator pulley, thereby resulting in a drop in rpms and thus a drop in the output of the alternator. You can see this in action by monitoring rpms and voltage while using the a/c.

The solution would normally be to switch to a smaller pulley wheel for the alternator to increase its revolutions at the same rpms. Problem is...I have no idea if this is available for DSMs.

Some info here... http://www.dsmtuners.com/forums/showthread.php?t=264918

I was wondering if anyone else has had experience with this? It's really noticeable too, like with the ac on I notice pretty bad stuttering on acceleration, and it decelerates faster than usual as well.

Right now the car does a little bit of stuttering on acceleration to begin with, and at times chooses to idle surge, but short from a boost leak test which I'm working on (car has been off the road for 6 months), I've done every step in Terry's Talon Troubleshooting and everything checks out ok.

ideas please! it's friggin hot out

i say just check your spark plugs/wires ... A/C shouldn't be causing that acceleration problem you are describing.. and do tell the results of your pending boost leak test...

Wow, I have this exact same problem with mine and I'm seriously considering just ripping the ac out and rolling down the windows from now on. Just for some more details on my problem, when I put mine on the second dot, I can hear the belt squeak over my music.
Probs just gonna rip it out.