need help with idle proble <did many many searches with no result

[jwasbury]

Originally Posted by mark houghton

What purpose does the AAV have then? Is it perhaps part of the smog air pump injection system (my air pump is deleted).

Now that we've thoroughly hijacked Ertech's original post, hopefully this will give him a few other potential sources of phantom air getting into the intake. That, and/or sticky linkage to cause the high idle symptoms.

Looks like the OP has an '89, so perhaps no AAV. I'm guessing the aux air device he's already ruled out as the problem through "hose pinching" is the AAR. I'm liking JFairman's diagnosis of wonky Decel Valve, as I'm having a hard time imagining how a throttle linkage problem could raise the idle speed with the car just sitting and warming up over time (which is part of the symptoms described).

I read (in the Bentley manual?) that the AAV bypasses air around the throttle for a few seconds at startup. Its supposed to shut off as soon as the engine fires and starts pulling vacuum.

So, Ertech...any news?

[ertech]

Thanks all
went today to a reputable Porsche shop .he told me my 89 has a Thanks
Erick

[ertech]

is the the aux air device the same a decel valve?
if so how do i test it?
thanks

[ertech]

8 hour later and still runs great anyone know why the use of o2 cured the problem???
THanks

[Ronnie's.930]

Here is a good, previous thread pertaining to some of the 930's idle/vacuum devices:

RPMs hang and fast idle

Ronnie

[Ronnie's.930]

Originally Posted by Ronnie's.930

Yep, that's it . . . the Porsche PET refers to it as the "Vacuum limiter" and it costs over $500 for a new one !!!

My 930 recently began idling very high (1700 or so) and popping quite a bit more off throttle and adjusting the air/idle screw had no effect. I tested the cold start unit and it worked perfectly . . . other previous posts suggested a bad AAV would have these symptoms . . . I have removed it (had to remove the diverter housing to do so - no space to get to it otherwise) and have capped all the associated ports . . . I will put it all back together and test it in a couple of days . . . BTW the AAV was full of black, rusty, murky water (not just a little, but full) . . . it must have been put in a parts washer last summer when it, and many other parts, were at a shop for servicing/powdercoating etc.

Several members of this board have removed this unit and say that throttle responce is much improved (at the expense of more off-throttle popping) . . . I'm interested to put this to the test. There are several old threads about running without the AAV in place . . .

R

So I just test-drove my car for the first time since removing the decel valve and reinstalling the diverter housing and such - VERY pleased with the results thus far (just a short drive, however) . . . the extremely high fast idle problem (which was not affected by any amount of adjusting of the air bypass/idle screw) is gone and throttle responce is much improved! There is quite a bit of off throttle popping and crackling (as others who did this mod said there would be) but no so much that I can't live with it . . . I can see where some would consider it obnoxious, however!

R