AAV idle adjustment (again)

Thanks for posting the links. I’ve been meaning to order a rebuild kit. I occasionally check @John_John1 eBay store and thought he was sold out. Turns out my preferences were filtering out his items. Selecting “Worldwide” instead of “Default” on Item Location brought up all of his items.

I did. It came with a plastic fitting on top, but after I cut it off, it was a direct fit.

1 Like

Yep, me too, although I don’t remember cutting off plastic elbow, i just removed it.

$5. To replace 1 year old OEM $60 one that was bad.

1 Like

Well I dunno, fired up the XJ-S today. Couple of things,
Might have found and underlying culprit. The back hose clamp wasn’t even clamped down for one thing. I started the
car went in to adjust the idle screw. Seems to go from cold
Start 900RPM to 700 RPM warmed up , creeps up to
750 - 800 RPM, might have to back off the screw but
seems to be honing in? Maybe.

It’s normal to creep up sometimes. When i take a reading, I drive it for about 20 minutes, move it from Drive to Park, let it settle for about 20 seconds, and then blip the throttle once or twice and see where it goes in 10 seconds.

I would really get a timing gun that measures RPM, it will be more accurate because it uses spark plug signal. I went through what you were doing, going for 750RPM on tachometer. Then got timing gun and found i had set it to 800RPM.

The AAV only needs clamps on the J shape between it and intake manifold. The air intake side doesn’t matter.

My tach also goes from 900 to 700 on tach, which is 950RPM to 750RPM when measured with my timing light. I think you’re good.

I mean I don’t know it settled down, I still think I’ m going to put the new kit in. I think the jubilee clip was contributing to the issue but here it is.

Just as a side note the stumble seemed to have cleared up.
Maybe a leak on the back hose?

A vacuum leak would cause a higher idle, not a stumble. Although if it was an intermittent leak, that could mimic a stumble?

Not sure if I’m quite there but getting close.
When I start the car cold it seems to go to a lower RPM
Say 600 RPM then it goes up to around 1000 RPM then
As the temp gauge barely starts to move it’ll settle back
To approx. 750 RPM which you can see in the pictures.

How long does it stay at 600? Just a moment or two? A minute?

This might be a fuel mixture issue?

Or one of the vacuum advance controls? I’d visit the ignition timing aspect of all this as mentioned by Jal5678 a few posting back. Some of the controls (if still operational) specifically pertain to cold vs hot engine timing

When was your last Italian tune up? You gotta make your idle speed evaluations and adjustments after your ITU.


Doug, I would say a matter of seconds, maybe 3 , I’ll pay closer attention on next startup.

Part of the issues with cold startup is that you have three systems all affecting idle on a cold start. First, the 45 second timer retards ignition to help warm up the cats to operating temp, reducing rpm. Second, the 45 second timer activates the secondary air valve (SAV) to help compensate for the ignition retard by increasing rpm. Finally, you have the AAV which should be fully open on a cold start. Any one of these not working properly will cause cold start idle issues.

Of course, the 45 second timer also activates everytime you start the engine, even hot. The rpm change from the ignition retard is never exactly compensated by the SAV.

I deleted the vacuum solenoid controlled by the 45 sec timer and deactivated the SAV function controlled by it. I now only use the SAV for compensating for the A/C compresser load.