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To remember, Jack - revs are tied to road speed; to increase rev you must increase speed. And to increase speed to need more power - which can only be had by increasing revs…
The point here is that if you push the pedal; the box should downshift, increasing revs - did you try manual downshift? Obviously, the engine lacks enough power to accelerate in the gear you were in - which leaves questions. Example; if you go uphill - you are supposed to be in a gear where the car can accelerate. If it won’t and you push the pedal; the engine will indeed ‘hick-up’ - it may get plenty of the wherewithal, but the rpms does not produce enough power. It’s the same engine reaction whether it is an automatic or a manual - and in the latter you must downshift…
All of which doesn’t mean that nothing is wrong. And that the engine later performed perfectly under identical(?) circumstances - an intermittent fault is possible. One may indeed be the CTS; while the sensor itself may be OK - the connector may be not be? Disconnect the plug and measure the resistance over the two wires - it should show some 2 Kohm. But importantly; bending and twisting the connector should not alter the resistance - an iffy connection may mislead the ECU intermittently…
Another factor is the dist; opening the throttle the ign timing should back off, if vacuum/centrifugal misbehaves intermittently - the engine will lack power. Have you checked your advance settings? And have you checked the box shift points…?
There is nothing externally wrong with your AFM - the sealing is just to keep out dust and water. A PO may just have had the AFM apart and being a bit sloppy with resealing…
I just read this thread and the symptoms described by Andy Morris are like for like. So, I am going to try the AFM capacitor fix and see what happens. Have you done this procedure?
The Jag Lovers archive suggests a 100 microfarad capacitor, however other contributors suggest a 25 or 33 microfarad capacitor. Do you have any view on the best one?
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I sure done it, Jack - and see no reason to deviate from the Jaguar specs…
In my case, the capacitor was already installed, but had failed - so soldering in a replacement was straight forward. Incidentally, I could not find a 25V rated capacitor, so I used a 16V - but 100 microfarad it was. Cured the problem…
But it must be emphasized that it is a specific cure for a very specific problem - it has no effect on anything else. Its likely caused by arcing in the AFM resistor sweep - giving wrong gen to the ECU. Symptoms; stuttering engine and very visible exhaust smoke during acceleration(!) while cold - no symptoms with steady pedal. Never present with the engine warmed up…so…
However, needlessly installing the ‘cap mod’ is harmless - it will not interfere with the engine; it just cures this very specific symptom…
Check your fuel filter and fuel pressure regulator/fuel pressure, but I agree also the dizzy needs removal and checking. I’m not sure if the ignition amplifier is a always a case of they work or they don’t. They can be upset and then fail due to heat buildup.
Good luck and yes it’s a beautiful car with the Sage (?) green metallic paint.
So I changed the plugs yesterday and installed the cap mod. Also did an oil change.
Plugs were pretty old and had crud on them - a couple of them were quite black.
I took her out yesterday, and the revving issue looks to have gone! But… Idle seems to have gotten worse and it sounds quite lumpy. It’s not misfiring but sounds like she’s chugging a bit.
If I recall correctly, the idle a while back used to be pretty smooth and rock steady, and now the rev needle moves up and down slightly and it’s generally a bit agricultural.
Nothing wrong with my coils then, Kirbert
Yesterday, I took her on a shakedown on the Autobahn and revved her up to 6000 rpm in second gear for a while. The roar and oomph that comes from the V12 beast is very impressive to say the least…
I do this once a month or so, when the engine oil is nice and hot, because I drive a lot of very short distance trips with her nowadays. Hey, it costs me some fuel, but the engine can burn clean by doing this…
As to the problem of the topic starter: might be a vacuum leak or a faulty kick-down switch…
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Again, the cap-mod has no effect on a warmed up engine, Jack - it’s purely to remedy a cold acceleration/load problem. It’s mentioned in the relevant Jaguar bulletin that the polarity of the capacitor is important relative to the two wires used when connected - but the effects of wrong polarity is not mentioned…?
Otherwise, you actions should not have any negative effects on idle - assuming the gap of the new plugs were properly set. But it may be worth while to test spark energy; use a spare plug gapped to 2,5 mm and connect to any plug lead. Crank the engine - the spark should be strong and blue. Weak sparks may cause occasional misfiring, and uneven idle…
Decided to bite the bullet and take her to the shop after unsuccessfully attempting to diagnose.
They just called and said that the timing is out by 8degrees (is this a lot?) but the distributor is currently stuck in situ (they are attempting to free up now with spray). Will post an update shortly.
