Missing hot
#41
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No time for testing this morning as I was recruited to move a 1942 couch. Before I had to leave I replaced the dual coils with the new Jaguar DAC6093. This made a significant improvement that was immediately noticeable and combined with all the aforementioned changes has almost gotten rid of the missing. But it is still there. Very steady and much smoother. Power up a bit perhaps.
I assume my cat meltdown a while back also damaged the O2 sensors. So I popped 2 new Bosch OEM O2 sensors in. Well, that certainly did something. At least when they're active. When I pull the link in the trunk I can hear the car seeking a good mixture. Idle up, down, up, down. Just slightly, not like it's revving up or anything. It wasn't doing anything like that before. Does this take time for the ECU to determine, or is this normal?
EDIT: re-read the book on this. One wire sensors on this car do this because the o2 sensors cool and stop functioning properly at idle.
Metering the monitoring link is confusing me. Does anyone have a clear set of instructions for how I should do this check?
EDIT: Apparently I'm doing this correctly, but I'm getting significantly different readings from the two sides.
Thanks for all the help so far everyone! This is sooo much better than it was! Mileage is up, idle is smooth with only an occasional blip.
EDIT: I also found this frustratingly pointed paragraph in Kirbys book.
I assume my cat meltdown a while back also damaged the O2 sensors. So I popped 2 new Bosch OEM O2 sensors in. Well, that certainly did something. At least when they're active. When I pull the link in the trunk I can hear the car seeking a good mixture. Idle up, down, up, down. Just slightly, not like it's revving up or anything. It wasn't doing anything like that before. Does this take time for the ECU to determine, or is this normal?
EDIT: re-read the book on this. One wire sensors on this car do this because the o2 sensors cool and stop functioning properly at idle.
Metering the monitoring link is confusing me. Does anyone have a clear set of instructions for how I should do this check?
EDIT: Apparently I'm doing this correctly, but I'm getting significantly different readings from the two sides.
Thanks for all the help so far everyone! This is sooo much better than it was! Mileage is up, idle is smooth with only an occasional blip.
EDIT: I also found this frustratingly pointed paragraph in Kirbys book.
IDLE STUMBLE: The mid-80's H.E. tends to "stumble" at idle when warm, even when it runs perfectly smoothly when cold or at higher throttle. This appears to be normal, although it is definitely disconcerting to an owner that spent the kind of money this car costs and expects better from his 12-cylinder engine. Fuel injector cleaning and/or replacement, spark plug replacement, and oxygen sensor replacement have no effect.
Last edited by JigJag; 01-04-2017 at 09:33 PM.
#42
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I have looked for the bracket for the new coil, would you happen to know the part no. ?
It's impressing to follow how much you get done to your car in short time. It must be quite annoying not to have nailed the problem yet, but now the goal is even more tempting: You will get in the Kirby book with the solution...
The following users liked this post:
JigJag (01-05-2017)
#43
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EDIT: I also found this frustratingly pointed paragraph in Kirbys book.
IDLE STUMBLE: The mid-80's H.E. tends to "stumble" at idle when warm, even when it runs perfectly smoothly when cold or at higher throttle. This appears to be normal, although it is definitely disconcerting to an owner that spent the kind of money this car costs and expects better from his 12-cylinder engine. Fuel injector cleaning and/or replacement, spark plug replacement, and oxygen sensor replacement have no effect.
IDLE STUMBLE: The mid-80's H.E. tends to "stumble" at idle when warm, even when it runs perfectly smoothly when cold or at higher throttle. This appears to be normal, although it is definitely disconcerting to an owner that spent the kind of money this car costs and expects better from his 12-cylinder engine. Fuel injector cleaning and/or replacement, spark plug replacement, and oxygen sensor replacement have no effect.
Greg
The following 2 users liked this post by Greg in France:
Grant Francis (01-05-2017),
JigJag (01-05-2017)
#44
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I have this operation on my task list, and the coil is already in my garage.
I have looked for the bracket for the new coil, would you happen to know the part no. ?
It's impressing to follow how much you get done to your car in short time. It must be quite annoying not to have nailed the problem yet, but now the goal is even more tempting: You will get in the Kirby book with the solution...
I have looked for the bracket for the new coil, would you happen to know the part no. ?
It's impressing to follow how much you get done to your car in short time. It must be quite annoying not to have nailed the problem yet, but now the goal is even more tempting: You will get in the Kirby book with the solution...
Last edited by JigJag; 01-05-2017 at 08:04 AM.
#45
#46
#47
#48
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The Jag version is an EAC5044.
![](https://cimg7.ibsrv.net/gimg/www.jaguarforums.com-vbulletin/576x356/screen_shot_2017_01_05_at_4_07_15_pm_cd6b022a92d1f1d837ef3e35d11664f6a959b064.png)
If it's not available, I believe that 2 of the parts I linked earlier can replace that entire part.
![](https://cimg3.ibsrv.net/gimg/www.jaguarforums.com-vbulletin/800x800/f119352252_f52c64d350c00db5d472be39974a042c610b073d.png)
If you went this route, you'd want to use two washers of equal thickness on the other two capstan bolts to keep the capstan level.
#49
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Here's a clip of the current idle, and revving.
https://clyp.it/2seagppw
My conclusion: Improper centrifugal advance performance was the root cause of this problem. Drive timing the car masked the issue as I added static advance that compensating for the lack of Centrifugal advance but making a smooth idle impossible. Fully advanced timing at idle is bad.
Timing it with a light to 18 degrees at 3000 w/o vac adv. would probably have made it obvious that I was missing some cent. advance, but perhaps not. Dizzy rebuild coming up...
https://clyp.it/2seagppw
My conclusion: Improper centrifugal advance performance was the root cause of this problem. Drive timing the car masked the issue as I added static advance that compensating for the lack of Centrifugal advance but making a smooth idle impossible. Fully advanced timing at idle is bad.
Timing it with a light to 18 degrees at 3000 w/o vac adv. would probably have made it obvious that I was missing some cent. advance, but perhaps not. Dizzy rebuild coming up...
#50
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JigJag (01-17-2017)
#51
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I'm pretty confident in my assessment of the C.Adv. not operating properly. I'll rebuild it regardless to be sure. Re-lubrication and a lot of exercise has changed it's behavior. It was not seized by any means. I have checked it numerous times. But it's action is smoother and easier now than it was.
I won't be running the V.Adv. direct from the manifold, as I want to use the dump valve. I will be checking all the components in the V.Adv. system again, Regulator and Dump ( edit: and WOT enrichment vacuum sw. ) valve are all that I am using.
EDIT: V.Adv. capsule is testing fine. Holds vac and smooth movement. I understand at some point Jag went to a "leaky" V.Adv. unit ( tiny hole ) to help the vacuum regulator function properly. Mine does not have this style. It is OE as far as I can tell.
The idle is beautiful now by comparison with before. If I can get the power and economy back to where it was with the timing too high I'll be very happy with it!
Last edited by JigJag; 01-06-2017 at 02:38 PM.
#52
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Well, I can finally put this topic to rest. The answer to your query is Yes. Direct port connection and all is well! No new vac advance capsule needed.
In the "Comedy is all about the..." thread I discussed correcting my ridiculously high advanced timing. After testing for actual TDC, it turns out that my timing gauge on the motor is reporting 10 degrees higher than the actual timing. I assume my pully has rotated on the rubber inner hub.
Correctly resetting the dizzy to 10 BTDC and testing her made it clear my timing was the issue. It was timed too high to possibly idle well! But, even following Grant's instruction ( dizzy eccentric screw at full retard and reluctor and pickup alligned with 1A at 10 BTDC ) I was getting a little detonation under heavy loading. I contemplated pulling the dizzy back 3.5 degrees on it's mounting screws and moving the eccentric screw to 3.5 forward on it's scale to give me room to adjust it. Fortunately I was reading elsewhere and found a suggestion to run the Vac Adv straight off the top ports on the RH Throttle body. I hooked up my vac gauges to check it out.
The top throttle body port provides NO vac at idle, and slowly climbs on throttle opening. I connected this port directly to my vacuum advance capsule.
The result is perfection.
![Icon Jammin](https://www.jaguarforums.com/forum/images/smilies/icon_jammin.gif)
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![Icon Clapclap](https://www.jaguarforums.com/forum/images/smilies/icon_clapclap.gif)
Buttery smooth idle like a kitten full of milk. Good power under load, no detonation, better throttle response! ( IMO ) I wish I had tried this when I first got the car and went through the vacuum advance system! It has literally transformed my experience driving this vehicle!
Future tinkering will include determining the max vac this setup provides and possibly adding the vac regulator if it is >10, drive-timing the static advancement to just below detonation levels, and possibly adjusting the response of the vacuum advance module ( mine is the adjustable variety ).
My summary, ported vacuum for the vac advance module is awesome!
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#53
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Grant Francis (01-18-2017)
#54