[v12-engine] How long should engine run with AAV inlet plugged?

Hello, I have been suspecting vaccuum leaks on my engine for
a while. The other day, I decided to plug the AAV inlet from
the left airbox to experiment to see how long it would take
for the engine to die or if the idle would be sustained by
my suspected leaks. To my surprise, the idle was unchanged
and it took several minutes for it to deteriorate but the
engine never died. I would be interested to know how long
the engine should run in those conditions so I would need
some of you with ‘‘no-issue’’ engine to duplicate my
experiment and let me know the results.
Thanks in advance,
Francois–
89 XJS Conv. Keisler Exhaust & 5 speed Mods
soddy daisy, TN, United States
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Francois, if you only blocked the AAV air inlet, the engine should not
stall. If you have one of the AAV configurations that has the port
partially open when warm, the idle many slow somewhat, but if the throttle
plates are adjusted correctly (0.002") and the vent hose from the
distributor is still connected to the AAV hose you will have enough air to
idle.

If your AAV configuration closes entirely when warm, you should see no
change by closing off the AAV air inlet with a warm engine.

If your throttle plates are adjusted correctly, the engine RPM on cold start
is about 900 to 1000, you can adjust warm idle RPM to 750 in “P” by
adjusting the 13mm bolt on the side of the AAV and you are not experiencing
RPM surges at idle, your engine is working properly.

Jim Johnson - NCJOC
'88 XJ-S, V12, Lucas (CEI), TH400 (w/B&M), Dana 2.87
Annapolis, Maryland

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In reply to a message from Jim Johnson sent Thu 30 Jun 2005:

Jim, thanks for your email. The next experiment, then, would
be to plug the L&R air boxes and the distributor’s vent hole
filter in addition to the AAV inlet and then the engine
should quit unless a lot of vaccum leaks, right?
Best regards
Francois–
The original message included these comments:

partially open when warm, the idle many slow somewhat, but if the throttle
plates are adjusted correctly (0.002’’) and the vent hose from the
distributor is still connected to the AAV hose you will have enough air to
idle.


89 XJS Conv. Keisler Exhaust & 5 speed Mods
soddy daisy, TN, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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“The next experiment, then, would be to plug the L&R air boxes and the
distributor’s vent hole filter in addition to the AAV inlet and then the
engine should quit unless a lot of vaccum leaks, right?”

Yes, there would then be no air intake and the engine should stall unless
you have serious leaks. I would suggest you remove the distributor vent
hose (the one to the AAV hose) from the distributor cap and plug it for your
experiment to prevent the engine from trying to suck air through the base of
the distributor with the vent inlet / filter covered.

Jim Johnson - NCJOC
'88 XJ-S, V12, Lucas (CEI), TH400 (w/B&M), Dana 2.87
Annapolis, Maryland

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