The car is idling right now around 750 to 800 rpm. When I turn on the A/C, it starts surging, and goes all the way down to around 500 rpm in some instances. After a little bit, it will just die. If I give it some gas to keep it running, as soon as I just let off, it will drop to around 500 and die right away. I've been trying to raise the idle temporarily to around 950 or 1000 so I can keep it running long enough to see whats going on. The problem I'm having is that it still idles at 750 to 800 regardless of what I set idle to in Idle Engine Speed vs. Temp. Tuner Pro Sensor data even shows the car running with the desired idle paramter at 800 rpm.

Is there any other table that controls idle rpm? I am looking through, but haven't found anything.

 

There is a table that adds rpm when you turn the ac on. Might try playing with that.

 

It's actually a constant in stead of a table, but it shouldn't make this much difference. The usual add-on is typically only 25-50 RPM.

How is your VE table? The cells immediately above where you idle (higher MAP KPa value) might need to be raised a bit. Another possibility is the compressor is about to lock up and dragging really hard on the motor....

 

Right it is a constant....Mine was 13 rpm.

Its not the rpm increase..But the computer changing the postion of the IAC. At idle a little change can do alot.

 

Isn't there an 800 RPM idle speed limiter in the f-body $8D code?

RBob.

 

Well, the A/C was working previous to the motor swap. If the car is fully warmed up, it can stay running with the A/C on, it just surges really bad, and will almost die each time. The surging isn't when the A/C engages and disengages. It surges while the compressor is engaged, so the issue is most likely IAC or fueling related.

I found what you were referring to, and it was set to something like 12 or 13, don't recall. I made it 50, and it didn't change anything. I made it 200 rpm, and it didn't help either.

I just took a look at my IAC counts, and they were at 160. I had set minimum air so that the counts were around 25 or so, but ended up leaving it at 0 counts later on. I was reading Grumpy's article where he runs 0 counts, and I had given it a try. Does the ecm control idle speed solely via the IAC? If so, that may be my problem.

I haven't tried to see what kpa the engine pulls at idle with the A/C engaged because I've been busy trying to figure out why it wouldn't idle higher than 800. I'll look into the VE table as you guys suggest.

I guess it would make sense that my request for a high idle is being ignored by the ecm if there is an idle speed limiter. Is that hardcoded in the $8D? I know I'm not the only guy with a moderate cam and A/C, so I figure this thing should be running fine at 800 rpm with the A/C on. Maybe I should focus on making it work like that than worrying why my idle isn't going up.

 

Yes, when in park or neutral it will go higher than 800 but as programmed from factory 800 is all it will do in gear.

I changed my bin toa allow more because I don't have a park neutral input wired into the ECM. I only need it in very cold weather though.

Sounds like the IAC is too far open when you're at idle and giving it the throttle to keep it running just confuses it more. Set the IAC valve where it's at about 20-30 when you're at idle and kick up the AC on RPM's a bit.

Maybe?

 

There's your answer. Your IAC is already at it's maximum for keeping the engine running at 800 rpms. You need to open the throttle-plates a little more. IIRC - your IAC should be around 10 all warmed up running at 750 rpms, not 160.

This also explains why, when you change the rpm base and rpm additions with AC on, you don't get any more rpms.

You MAY have to reset the IAC as well... I forget exactly something like ignition on, pull IAC, turn off, put IAC back on. I forget, I think this is in the Tech Articles.

Good luck.