Closed Loop/AC ON?

[Funracer]

According to this:

http://www.teamzr1.com/ubbthreads/ub...at&Number=1586

In modes 3 and 4, is it saying that the car is in CLOSED LOOP
only if the the A/C is selected ON?

In other words, if the A/C is OFF the car will always be in
OPEN LOOP in any mode?

If so it seems like an easy way to force the car into OPEN LOOP
operation for troubleshooting purposes.

Or am I reading it wrong?

Thanks

[VetteMed]

Originally Posted by Funracer

Or am I reading it wrong?

Thanks

Yes, you are.

That chart lists the things that the ECM looks for under those conditions. Not the things required to "force" an open or closed loop status.

[Funracer]

Hi VetteMed!

Here is my simple but annoying problem:

A/C ON, car idles terribly, almost will not stay running
unless I goose the throttle.

A/C OFF car idles like it was brand new and runs perfectly otherwise.


What could it be?

Thanks,
Neil
91 #301

[VetteMed]

Neil, first (easiest) thing to do would be to remove the IAC (idle air control) motor, RH side of the throttle body. Clean it with carb cleaner thoroughly.

Other possibility is that the compressor may be failing and is difficult to turn? With the engine off, you can try to turn it by hand. Not the part the belt rides on, as that will freewheel, but the part that is just behind the belt contact surface. That's directly connected to the compressor shaft. It should turn fairly easily by hand. If it's not moveable by hand, perhaps it's on the verge of seizing up.

I'd also probably try to start the motor, hold the RPMs at about 1500-2000 rpm, then engage the AC compressor (via the button) and see what happens.

[Funracer]

I am away from home until this weekend.

I can tell you that when I do this:

I'd also probably try to start the motor, hold the RPMs at about 1500-2000 rpm, then engage the AC compressor (via the button) and see what happens

...I can cycle the AC switch on and off repeatedly and it will idle
poorly with the AC on and well with the AC off. I have had this problem
for a while and just noticed recently that it runs very differently when the
AC switch is ON vs OFF. One of the few mode differences in that link
above is that "AC Select/AC Request" occurs only in the Closed Loop
modes (3 and 4) and nowhere else so I thought they might be related somehow.

Neil

[VetteMed]

Neil, I think you're misinterpreting that chart.

I can have the AC compressor running the instant the motor fires, when it's still in open loop. It will remain in open loop regardless of the AC request. It will enter closed loop when the parameters for doing so, have been met.

[Funracer]

When I start the car (key on) the AC is already on.
I don't remember it being like that years ago. Is that normal?

Thanks

[VetteMed]

If you had the AC on when the key was turned off, it will still be on when you restart. Normal behavior.

It's not normal for the system to turn itself on, if it was off when the key was turned off.

[Funracer]

I replaced the primaries a few years ago with Accell's and they all still
test normal. The secondaries are original and 2 of them tested bad (in the 6's) recently. While I realize they need replacement, I am keen to fix the
low RPM issue first.

Can bad secondary injectors affect low RPM driveability?

Thanks

[sammy]

it could if they are leaking