So I installed a full a/c system I found and have it charged. I have had the pfc running with motor already before adding the a/c so anytime I switch it on, the engine pretty much stalls. I redid the idle learn process and the only way I can get it working right is having the regular idle at like 2k rpms so when the ac kicks in, it drops to 1200. Is there a way to test if maybe the ac clutch is bad and drawing the engine down too much or is it just more tuning with idle and the IAC?

 

The stock and PFC ecus will increase idle air flow to compensate for the drag of the AC compressor at idle.

When my PFC controlled FD went to large secondary injectors, the Air Control Valve had to come out. After that the 3 PFC idle speeds did not work. So I went 100% manual idle. Thus with my stock ports that could idle very low, I set my AC on idle at 950 rpms. When the AC went off, the rpms would increase to about 1300.

I lived with that for a while before coming up with my own fix. I could not use the stock idle control solenoid because it was removed when I modified my UIM for better air flow. So I purchased a large air solenoid and an adjustable Hobbs air pressure switch. The solenoid turns on when the AC compressor turns on and allow air from the intake tract to flow to behind the throttle plates utilizing the large PCV pipe in the UIM. Now with 950 idle without AC the revs go up to about 1150 with the AC on.

The Hobbs switch is set to deactivate the AC at about 5 psi boost.

 

You know I had thought the acv was for the air pump... I don't have mine either and have been having issues with the 3 idle settings. May have to try the manual idle next. I still have the iac though.

 

The ACV is for the air injection into the stock exhaust manifold, and also into the main cat. But there seems to be weird wiring for the ACV that affects the Idle Speed Control. Especially if you cut off the unused/not needed connectors.

A friend's stock car idled correctly. He went single with large secondary injectors.
We removed the ACV to install the injectors and installed the single turbo. All without cutting off any connectors. His ISC for idle did not work. So we took off all the solenoids from the ACV and connected them back to the harness. The ISC still would not work.

 

Yea I had all the settings put in and one day it did fine and idles around 950 with no load and when the ac turned on it would raise to the set 1200 rpms, but then the next day it didn't do it and would die with the ac. The thing I did change was the ac relay fix as I only had the first low speed working with the pfc. Now I have all four but it seems weird because usually the fans should come on with the ac but it seems the fans only work off of the coolant temp as if its cool, the fans will be off even with ac on.

 

Getting a smooth idle on a PFC is a known problem. Believe the best you can get is a somewhat high idle that doesn't stall out when load (a/c) is applied.

 

I feel like i need to find a way to test the a/c compressor drag because to drop 300-500 rpms during engagement seems like alot to me. I mean these are pretty old compressors that maybe have sat for a bit, but I put the oil in with the 134 and swapped all the orings so its holding and cold.

 

It's not the compressor, it's the control system. I don't even have A/C, but when I hit the A/C button, revs drop like 300-500 as well (the fans do come on tho)

 

Interesting. Well starting over on the map as I think the map sensor(no name gm sensor) I had with the settings was off. Gonna change back to the stock one so i know the settings are right.

 

Making progress. Basically went back to stock pfc and map with settings. Found and fixed the clutch switch and dashpot. Still have some random stalling with ac on full as well as a higher idle than I want. Seems there is some circumstances that the ecu sees with switches that bring the idle nicely at the 900 setting.

 

And just as easy as it was, now it acts like a totally different car with almost 300 miles on the rebuild. Now the idle lowered and richer. Trying to redo it again, but may just give up on having the ac at idle working right. Might just drive the beltway a couple more times for the breakin so I can take tuning more seriously instead of just guessing with the rebuild.

 

idle tuning is a major weakpoint of the PFC unfortunately. There are a lot of things the PFC does well, but you have very limited control over how the ECU controls idle in specific situations.

 

One reason I went to non PFC idle control with all three idle speeds at 0, it allows me to run any idle timing I want to. When the PFC control idle, it runs a hidden non adjustable timing idle map.
Running this way allows more timing (even negative split) idle with less fuel for better cleaner idle.

The down side is that I have to tweek the idle timing and fuel between summer and winter.
But that is no big deal to me. I was raised on twin Weber DCOE40s/45s.

https://www.google.com/search?q=dcoe...Ft7mTcjXi2M%3A

Yes I have owned Alfas!

 

I was raised on dual Stromberg's

 

So I went manual idle for now until I get enough miles on the engine. Been going around the outer beltway a couple times and have around 350 miles on it so far. Does alot better idling this way then trying to fight it the other way. Eventually I will have to dive into it though.