Closed Loop/AC ON?

[Funracer]

According to this:

http://www.teamzr1.com/ubbthreads/ubbthreads.php?ubb=showflat&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]

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

[VetteMed]

correct. at idle they will not be operating, so the only way they'd affect idle would be if leaking.

[gbrtng]

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.

However, the AC defaults to AUTO when you reconnect the battery.

[Funracer]

However, the AC defaults to AUTO when you reconnect the battery


Thanks. Good to know.


at idle they will not be operating, so the only way they'd affect idle would be if leaking


In an earlier thread I had a fuel pressure problem that was ultimately resolved. During that process I did the fuel pump amperage draw test
described here:

http://www.zr1.net/forum/showthread.phpt=16978&highlight=amperes

My pump/pumps only drew about 5.5 amps should have been over 8.
Either one is not working or is very weak. Both pumps are new and I
have had this issue since before changing them. But I am thinking this
area needs further investigation. Maybe a wire or relay problem.

I will get to it next week and update if I find anything interesting.

Thanks

[Funracer]

My pump/pumps only drew about 5.5 amps should have been over 8.
Either one is not working or is very weak. Both pumps are new and I
have had this issue since before changing them. But I am thinking this
area needs further investigation. Maybe a wire or relay problem.


Rechecked the pumps draw last Sunday. As I guessed, now that the disconnected fuel line has been reattached the pump amperage draw
is back to normal. It now shows 9.47 versus the 5.5 mentioned earlier.

So I am back to square one. The car still starts and runs fine as long as I leave the AC off. As soon as I push the AC button the car will not idle and will not run unless I blip the throttle.


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 did check the compressor as VetteMed suggested. It did turn firmly
but smoothly (no binding) by hand.

The only thing I know for certain that is wrong with the car from
a mechanical perspective is that the secondary injectors are shot.
I have been reluctant to spend the time and money to replace them
because I felt certain they could not affect low rpm driveability.
But I don't know what else to check. Unless someone comes
up with something else to look at I guess I will be putting new
Accels in the secondaries next.

Regards

[VetteMed]

If your power key is still functional,leaving it "off" takes the secondary injectors offline, and therefore rules them out as a source of a driveability issue.

[4-cam]

My 91 had the same issue, Idled poorly with the a/c on. When the a/c clutch engaged it changed the idle 200-300 rpm. Stock injectors ohm 'ed out good and passed the leak down test. I changed them anyway. Now it idles great, no fluctuation in idle speed. I bet yours are leaking. Does it smell rich at Idle?

[Funracer]

If your power key is still functional,leaving it "off" takes the secondary injectors offline, and therefore rules them out as a source of a driveability issue.

I would expect that as well. The power key has no effect on the problem whether on or off. I also cannot see where turning the
AC on/off would effect driveability, and yet it does.

My 91 had the same issue, Idled poorly with the a/c on. When the a/c clutch engaged it changed the idle 200-300 rpm. Stock injectors ohm 'ed out good and passed the leak down test. I changed them anyway. Now it idles great, no fluctuation in idle speed. I bet yours are leaking. Does it smell rich at Idle?


It does not smell rich ever. I need to be clear about this tho. Turning the
AC on does not just affect the idle a little bit. It ruins the idle. The car will not idle. It begins to run very rough and will shut down in less than 10 seconds unless I keep blipping the throttle or shut off the AC.

I know the secondaries are no good so I will change them out just to
eliminate any doubt that they are having an effect.

Anyone know the Accel secondary injector part numbers?

Thanks

[VetteMed]

.

Anyone know the Accel secondary injector part numbers?

Thanks


Same as the primary part number. 150821. You have to grind off the tab on the connector in order to use the Accels. Not sure if that's on the primary or secondary side though.

[Pete]

Check/clean/replace your IAC.

Pete

[Funracer]

Same as the primary part number. 150821


Like these?

http://www.amazon.com/gp/product/B0006HJO3G/ref=ox_ya_os_product

Good price I think.

Will report back after install. Next week I hope.

Regards

[VetteMed]

That looks like a very good price for those!

[Funracer]

I spent a long time today putting a new set of Accels into the
secondary position. Accels were put into the primary position about three
years ago.

When I got the plenum off I found this:

http://i22.photobucket.com/albums/b341/yellowLT1/Door/CIMG6950.jpg

Not good. It was the tube that comes out between the right rear
plenum gap. Notice the zip tie that I had put on years ago. I pushed
it back in and put another ziptie on tightly:

http://i22.photobucket.com/albums/b341/yellowLT1/Door/CIMG6951.jpg

Warning! Car porn ahead:

http://i22.photobucket.com/albums/b341/yellowLT1/Door/CIMG6957.jpg

I have not pulled the plenum in about 8 years. I don't mean unbolt it
and tilt it up with a 2x4. I mean remove it in order to replace the fuel injectors. The difference is important because removing it completely
adds difficulty and reinstalling it becomes much harder, especially if you are by yourself. Here is why:

http://i22.photobucket.com/albums/b341/yellowLT1/Door/CIMG6960.jpg

I left the socket on to accent the problem. There is a small bolt there that locks the canon plug to the underside of the plenum. The wires run into the plug are quite short - no slack, at least on my car. That makes it difficult to lift the plenum much more than 45 degrees or so. Thus the 2x4 for some applications.

However, to completely remove the plenum this plug needs to be unscrewed from the underside. Due to very limited acces it is tough to
get at. The hard part though is putting it back on. It took me about
2 hours to completely remove the plenum. Another hour to remove
the fuel rail and replace the original (1991) Multitecs in the secondaries with new Accels. Notice the two different types in this pic prior to FI replacement:

http://i22.photobucket.com/albums/b341/yellowLT1/Door/CIMG6954.jpg

[Funracer]

Continuation:

Once I got the new FI's put in I had been at it for awhile and was starting
to fade. But I figured that reassembly would be quicker so I pressed on.

I put the fuel rails back in and began to reinstall the plenum. I soon found that the under plenum connector would not stretch to the plenum in the
"up" position. I dropped it into the "down" position and after some wrangling was able to get the male and female halves lined up by reaching around the back of the plenum. I turned the socket (see previous post for pic) but could not for the life of me get it to thread in. After trying
for 20 minutes, I gave up and tilted the plenum up again. I rerouted the plug wires over
the top of the tube as shown. Compare to the photo in previous post:

[Funracer]

http://i22.photobucket.com/albums/b341/yellowLT1/Door/CIMG6961.jpg

I was then barely able to press the coupling together and get the bolt
to thread on. All in all it took me over a hour just to get that stupid thing
back on to the underside of the plenum and then continue with putting all the rest of it back together. All told the entire project took 7-8 hours and flat wore me out. My back in killing me.

The end result? No change in my idle problems. Changing the secondaries was a long shot but no $$ wasted as they were shot anyway.

I remebered as I went that I had similar issues when I did this years ago.
If anyone knows a trick to make this part easier I am all eyes.

Sorry for the multiple post. It would not let me put it all in one.

Tired

[VetteMed]

I feel your pain. I curse that 1/4" bolt on the large connector every time I pull the plenum. I've found it's easiest when you scoot the plenum forward a little bit to allow access with a 1/4" drive ratchet via the RH side. There's a little room to get in there if you scoot the plenum forward a bit.

As for that vacuum hose, I usually use some rtv adhesive or silicone adhesive to hold the tube into the rubber elbow. I've gotten through an entire plenum R & R only to find that those vacuum lines came undone during reinstallation.

If you have access to a mityvac or other vacuum pump, pull the connector off the RH side of the plenum (between the middle sets of runners) and see if you can pull a vacuum. If so, your connections are OK. If not, you've got a leak.

[Funracer]

I feel your pain. I curse that 1/4" bolt on the large connector every time I pull the plenum. I've found it's easiest when you scoot the plenum forward a little bit to allow access with a 1/4" drive ratchet via the RH side. There's a little room to get in there if you scoot the plenum forward a bit.

As for that vacuum hose, I usually use some rtv adhesive or silicone adhesive to hold the tube into the rubber elbow. I've gotten through an entire plenum R & R only to find that those vacuum lines came undone during reinstallation.

If you have access to a mityvac or other vacuum pump, pull the connector off the RH side of the plenum (between the middle sets of runners) and see if you can pull a vacuum. If so, your connections are OK. If not, you've got a leak.

Plenty of cursing here as well. Mine was mostly directed at whoever
designed it that way to begin with. I do have a Mityvac and will check
as you suggested.

My next step in troubleshooting is to clean all the grounds I can find.
Will update then.

Thanks