Hello all

This is a Fluke 97 capture of a 2-pin  rotary AIC off of a 91 Saab 900T 5spd (similar ones used on VW, Volvos, etc)

The waveform looks fine, IMLE or are those slight lateral glitches in the on/off V lines significant and not artifact?

However, what's perplexing to me is that the AIC, when pulled a few days ago, was seized (by wooden tongue depressor into gap and the quick longitudinal-axis  'wrist snap' . Soaking/cleaning/lubing did not help.  It did, however, open/close when battery voltage was jumped to it

Also, idle is fairly stable about 80% of the time at spec'd 850 RPM; 20% of the time it swings between 600 and 1000, sometimes with some ~1 sec interval rapid pulsing; and very rarely a high 1500 RPM.

Sometimes tapping the valve stabilizes the idle; other times not at all

I'm also pursuing other idle-related pathways.

Hopefully the URL below will go through



Waveform sample of a mildly/moderately sticking rotary AIC? And/or what would I see on the scope?


Thank you for any comments,

DirkP in Northern CA, USA

http://new.photos.yahoo.com/dirkpi/photo/294928804156500417/0

Dirk,


Quote:

The waveform looks fine, IMLE or are those slight lateral glitches in the on/off V lines significant and not artifact?

Signal integrity looks good, yes.  The 'steps' in the waveform are not from the signal but the scope limitations.  At thet time base, your sample rate is only 762 Hz and it's an 8 bit scope.  Depending on the signal frequency it might even be aliased.


Quote:

Also, idle is fairly stable about 80% of the time at spec'd 850 RPM; 20% of the time it swings between 600 and 1000, sometimes with some ~1 sec interval rapid pulsing; and very rarely a high 1500 RPM.

Probably trying to bring the idle down using fuel cut, so you get that regular surging as the injectors cut in and out.  You are probably not going to be able to see the valve sticking in that type of a pattern unless you can determine if the valve follows the command.  A scanner might be a better tool for that if you have that parameter in the data.  I am not a Saaber, so others may be more familiar with what is available in the scan data.

Sounds to me like the valve is most likely sticky and in need of replacement.  

Thanks, Tom.  I should have just KISSed and said "Can an AIC/ICV have a good-looking waveform and still be bad?"  ;D

I have another used one on the way

Dirk