Dead Aux Air Regulator?

[echrisconnor]

The tuning of my CIS system obviously has some issues due to the PO. I've been going through them trying to work them out and beieve I've found a problem with the Auxiliary Air Regulator.

I pulled off the hose from the auxiliary air regulator yesterday and looked inside. When the engine is cold the door is almost completely shut. Based on what I've read in archived threads -- this is a problem, right?

The car starts reasonably well but once warm idles high. I suspect settings have been jacked up in order to make it idle. The idle adjust screw does nothing. When I pulled the hose off the AAR and started the car, it started and then died immediately.

Replacement of the AAR seems easy enough. $137 here at PP. Can it be repaired though? I tried manually pulling the door back to see if it was stuck. In moves freely but springs back to the near- closed position. The heating element reads 36 ohms and it does get voltage when the car is running.

[Superman]

exploratory surgery.

[TurboRuf]

echrisconnor,

I don't completely understand how the AAR is supposed to work but I can tell you that mine looks the same when the car is off. The spring-loaded disk covers about 3/4 of the passage.

[echrisconnor]

The AAR is supposed to be almost completely open when the engine is cold right? By cold, I mean about 70 deg F (the temperature of my garage in the AM).

[RarlyL8]

This sounds very familiar.
I yanked my AAR out last night. It was 1/2 open with the car cold. I put it in an oven at 50C for an hour to see if the bimetal spring was functioning. It closed about 3/4 or a bit more. The 12V test is next.
The units are not designed to be repaired. My guess is that the bimetal spring is tired. When the valve is nudged with a slim screwdriver it freely moves.
You can't pull the hose off to check its function. A huge vac leak will result. Leave the AAR in lpace and block off the vac line. My car starts up fine without it. They do not function in helping you start a cold engine, only to keep it running once started.
I plan to ommit this pesky device and just manually throttle the car on cold mornings.

[echrisconnor]

I pulled the AAR last night to see if I could repair it.
The first step was to drill out the rivets and open it up. Very easy. Inside the device is just a straight bimetal spring with a heating element around it. The bimetal spring is slightly deflected probably from age which is why the door is closed by default.

I see two options for repair:

1. Take pliers and bend the spring back a few degrees so they keep the door open.

2. There is a press fitting at the base where the spring attaches to the body of the regulator. I could drill a hole opposite this fitting, tap a screw in there and use the screw to push the whole spring mount back a mm or two. This may work, but I can't tell.

Does anyone have an opinion one way or another. Is bending a bimetal spring a good way to render it useless?

[targa80]

Since you have gone to the point of opening the unit up to investigate the problem you might as well tweek the spring a little to see if it works. What harm can it do except save you the cost of buying a new one. I think drilling a hole and tapping an adjustment screw would not work. Since the bi-metal is effected by heat adding an additional metal point would create a heatsink effect. If my AAR wasn't working properly this is what I would do before buying a new one.

[echrisconnor]

Over the weekend I tweaked the bimetal spring in the AAR and reassembled it. I set it up so that at room temperature it was about 2/3 open. After put in the refrigerator for half an hour, it would be full open. I wired the heating element up to the battery, and it closes completely after a few minutes. The rivets were replaced with bolts and lock nuts. Back in the car, the car starts properly; the idle is high (2k rpm or so) when cold, and then gradually decreases to 1k over a few minutes of warming up. Seems like this was an easy fix.

[targa80]

Great! Glad to hear the DIY'er repair project worked. Nothing more satisfying than fixing a problem on the Porsche. Except for great sex, a pint of Guiness, and winning the lottery.