Phil in Ar wrote:
In reply to a message from Frank Andersen sent Thu 2 Feb 2012:
Thanks for the comments, Frank
‘‘I think 1/8’’ is too little to safely provide fast enough cold
idle to start…half open seems to be the ‘norm’…run the
engine warm and verify that it actually closes completely
when hot…‘’
The AAV was closed completely at 80C on the dash gauge and
78C measured at the AAV body. My spare AAV on the parts car
had a similar 1/8 inch opening at the 50F ambient. Anyone
checked their AAV opening at similar temps?
We are still awaiting answers to that, Phil - a direct question to the
list for a heads up…?
‘‘The best test of the Thermotime is to connect a test lamp
across the (disconnected) CSI plug - then turn and hold the
key to ‘crank’.’’
I did do this yesterday and the lamp lit. I tried it again
today to check the ON time and it went out after 4 seconds,
then 2 seconds, then 1 second on successive cranks with a
brief pause between. Is the Thermotime cycle independent of
the draw through the CSI connector?
The TT is an ‘independant’ agent, Phil…
The CSI is connected to ground via a bimetellic strip in the TT - as the
key is turnd to ‘crank’ power is applied directly to both the CSI and
the TT. In the TT a heater coil heats the strip causing it to break the
CSI’s ground connection - and the CSI stops spraying. The TT reacts the
same whether ot not the CSI is connected…
As the strip cools down it ‘resets’ to ground - but the time for the
reset will depend on engine temps - so your observations are as
expected. With engine, or ‘strip’ temps above 35C the strips is not
grounding - and there is no CSI action…
‘‘And testing the TT to spec doesn’t really prove that the
CSI is actually spraying’’
Agreed, although I did go through rigorous testing of the
CSI last August running over 100 four second cycles testing
for a consistent spray pattern and lack of leaking after
spraying. That was just 200 miles ago.
It’s then sort of unlikely to be the CSI; as the engine catches it has
done its dash - and the engine, all well, should be supported by the
normal ‘cold engine’ fuelling. In principle, if you maintain the key to
‘crank’ for 4 seconds, whether or not the engine catches the TT goes to
its maximum - so if the CSI is actually spraying a non-start has other
explanations…
‘’…remove air duct and clean out the throttle body- then
verify throttle gap to 0,002’‘, and confirm hot idle.’’
The throttle body was cleaned and .002’’ gap confirmed last
August (200 miles ago) after I discovered dirty raw gas in
the manifold from the leaking CSI and tested and installed
the spare. I had also changed the AFM at the same time and
one or both changes solved the prior refusal of the engine
to rev past 3500 RPM. Hot idle is 950 to 1000 RPM in neutral.
Which is a mite high in itself - but seen in conjuntion with the 1100
rpms you reported with the engine cold; your AAV, ‘wrongly’, contributes
very little, too little extra air. One would expect cold idle to be some
200 - 400 rpms higher than the hot idle set…so…
‘‘I still strongly suspect the AAV being inadequately open,
Phil…the AAV is there to provide extra air to give the
engine enough power to overcome the cold drag. The initial
misfiring and the comparatively low cold idle indicates as much’’
What should cold idle in neutral be, and can it be adjusted
independently of the idle air screw for normal hot idle?
There is no independant adjustment of cold idle - and the cold idle,
courtesy of the AAV should be ‘much’ higher…
Or
is that what the AAV is supposed to do? Adding more air for
cold starting is a bit counter intuitive unless the ECU is
also adding more gas at the same time.
A cold engine has a considerable drag/friction - and the AAV adds air to
increase engine power. Note that the more air an engine gets the more
petrol it can burn - and the more petrol burnt the more power is
developed. Cold engine drag might be so high that the engine is unable
to idle cold with the hot idle setting - and if it cannot idle it cannot
start…
Is the air passage
through the AAV similar to the throttle butterfly being
slightly open, but automatically controlled?
The different air passages is somewhat conjectural; the throttle gap and
idle screw together give the hot idle - but the proportion is variable
with the throttle gap set. Nominally the AAV should add some 50% of
those together - as a guestimate…
It took four crank cycles this morning in ambient 54F before
it would keep running, and idle was first 900 and then 1100
rpm after 15 to 30 seconds. Pressing the accelerator after
it first starts will make it stall unless done very very
slowly.
It all implies that the AAV is not doing its job, but other factors
cannot be excluded - such symptoms are not really exclusive to the AAV.
If the engine develops too little power in idle it may baulk at sudden
pedal inputs - and a Jaguar should not do that, hot or cold…
*remove air filter and once the engine is idling, very slowly push on
the AFM flap. If the rpms rise and or the engine stabilises it signifies
lean running - pushing on the AFM flap simply increases fuelling. With
correct fuelling the engine should misbehave as soon as the flap is
touched…
Another point relating to this - if you have the O2 sensor; with the
engine idling hot; disconnect the sensor. There should be no engine
reaction - signifying that the ECU does not require Lambda assist to
rectify fuelling. The point here is that while hot the Lambda does this
- but it is inactive with the engine cold…
The most frustrating thing is that the Sovereign
had always been the best starter in the cat house until lately.
It will be again, Phil - when this is sorted…
Frank
xj6 85 Sov Europe (UK/NZ)>The original message included these comments:
However; I think 1/8’’ is to little to safely provide fast enough cold
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