Idle Problem

bob hodges · 05-26-2002, 07:17 PM

I just got my SC back on the road after three months with the engine out. I now have a condition that needs attention. The engine starts ok and idles @ 900-950. This is Phoenix and the weather is beginning to get warm. When the engine is running at normal temp, the idle keeps climbing up and will idle at 1400 at the stop lights. I have read all the threads on this subject but nothing is mention about this condition. Does this sound like a vacume leak? Should I be looking at AAV or some other compoent?
I am thinking this problem was not there prior to the engine removal. Leads me to think I have distributed something. Any suggestion where to start?

Bob 80SC

dougcl · 05-26-2002, 11:14 PM

Make sure it's not just a linkage problem. Put your foot under the pedal and pull up.

Check the connector to the Auxiliary Air Regulator. Make sure it's actually making a connection by ohming it back to the 14 pin connector. If this was disconnected and reconnected when the engine was out, the connector may have been damaged inside.

-Doug

bob hodges · 05-27-2002, 05:58 AM

Doug,

I have checked the linkage and all appears to be normal. Its funny you should mention the 14pin connector, because if you didn't notice a few days ago I was asking for help in the diagram of the 14 pin connector. I lost the wires during the removal of the engine. The backshell on the plug popped off and the wires were spring loaded to the out position. I have since accomplished the correct positions on the pins but, I have a broken female side on that 14pin connector and I have one on order with Porsche. I don't think our host carries these.

Bob 80SC

dougcl · 05-27-2002, 08:29 AM

Bob, ohming back to the connector might be a pain now that I look at it. Looks like the power is found on pin 10 of the 14 pin connector (I'm looking at a 1978), but there are three devices in parallel at that point:

1) Warm Up Regulator
2) Supplementary Air Valve
3) Thermovalve

The other side of each device is just ground.

Ohming would require disconnecting two of the three for each device you want to test. Unfortunately the terminology is inconsistent. I'm not sure what the difference between 2 and 3 is. Maybe someone else can chime in here.

Regarding the busted 14 pin connector, been there, done that. I was fortunate enough to find one at a junkyard.

-Doug

bob hodges · 05-27-2002, 10:40 AM

Doug,

I will do some looking into the power distribution, I just went out with the car and drove it to see what was happening. The idle is 950 at start up and the idle follows the oil temp. Seems to peak at 1400RPMs This tells me that the AAV is not opening? or should it close at temp?

I think if I adjusted the idle screw, I would only be fixing the idle and not the cause.

Bob 80SC

dougcl · 05-27-2002, 10:22 PM

Bob, the AAV should be closing as the car warms up. There is a little helper heater in there to keep it closed. I suspected the connector to this heater.

You should be able to disconnect and block the vacuum lines going to the AAV to test it. If the idle drops when you do this, the AAV is not closed.

-Doug

bob hodges · 05-28-2002, 06:53 PM

When I disconnected the vacume line I discovered that someone had blocked off the line with a screw stuffed in the end. What is that all about? I though I saw someone on this BB tell of blocking off this line. I ran the engine until warm and adjusted the idle to 950. I am hoping that cures the problem.

Bob 80SC

dougcl · 05-28-2002, 09:13 PM

Bob,
I saw some of the discussions here about blocking off and disabling some of the CIS devices, but I didn't really follow the reasoning. Maybe one of the people advocating this could chime in here.

If your AAV is permanently blocked off, then that could explain why you are having a problem. The idle screw is set to supply enough air when the engine is cold, and since there isn't any compensation from the AAV, so you are getting too much air when warm.

Perhaps the AAV was blocked off because it stopped working. I think a good starting point would be to get the AAV reconnected and working properly, then adjust the idle screw with the engine at temperature and see if that solves your problem.

-Doug