In search of the best idle for my 1986 XJ6 Series 3. I was having large idle drops with AC on when in drive. Idle had to be upwards 1200 when warm to prevent stalling. Ruled out all the main things that I found on the forum. My trusted mechanic thought the only thing that made sense was some cracking in the exhaust manifold that was screwing up the mixture. He also said that he had previous luck switching to a MSD ignition system and a MSD coil. The scientist part of me thought it would be interesting so I had him do the switch. I've been driving with the new system for the last month and have a few observations. I'm happy with the smoother idle and the 10% improved mileage number. Performance seems the same to me.

Three times in the last month, I've had the system cut out for less than a second on acceleration under load (uphill) - which is starling, but it's only a split second cut out and its like a glitch in the matrix. My mechanic said its an adjustment issue he can fix. This car is becoming more and more fun the more work I put in it. It's like a German Shepherd as pet dog. Challenging but beautiful.

Ignition Module MSD A6L and Ignition Coil is HVC2.

 

Did you have to install a " MSD Ignition Tach/Fuel Adapter" to get Tach and EFI to work correctly?
Rgds
David

 

I have read swapping out the ignition does make an improvement. I assume the MSD eliminates the ignition control module? I have a Pertronix distributor and coil to install and am hoping for some improvement as well. I have read where the timing does have to be adjusted.

 

There are two Pertronix distributors for XK 6 cylinder engines:
D177600 with matching 3.0 ohm coil (40511) for replacing points distributors.
D171618 with matching 0.6 ohm coil (45011, 45001,or 45111) for later cars.
The manufacturer does not recommend for Jaguar EFI engines, but numerous forum members report good result on XJ6 S3 installations. (my view is; they could not get California ARB approval, except for points distributors and carbureted engines as a direct replacement)
The advance curves are different than Jaguar OEM distributors, so must be timed at static settings with Pertronix instructions. At 3000 RPM both Pertronix and OEM will be at same advance ~ 33*
The increase performance comes from the lower resistant coil that allows more energy for spark with out burning the points or over heating the coil. New distributor and coil does not use the OEM ignition amplifier.
Rgds
David

 

Quote:

The manufacturer does not recommend for Jaguar EFI engines, but numerous forum members report good result on XJ6 S3 installations. (my view is; they could not get California ARB approval, except for points distributors and carbureted engines as a direct replacement)

I would agree.

The Bosch/Lucas EFI is very rudimentary and the ignition tie-in is a simple off/off voltage trigger. I don't think the EFI knows or cares if such trigger is coming from the Lucas CEI system or the Pertronix system.

That's my take, at least.

Cheers
DD

 

Hi David - I did not need to use the Tach adapter. But it took some work. The ground was apparently poor and after a new ground wire was attached to a sound location, the tach worked.

 

An update to my post about the MSD mod.

I had mentioned how the car sometimes would hesitate or hiccup on acceleration. A big backfire a week or two later caused the problem to be obvious -- the valves were not working properly on cylinders 3 and 4. Compression was terrible. I opted for a rebuild of the head. Boy - what a difference. Probably hasn't run that smooth since the mid 1980s. Idle is 500 with AC on and maybe 600 without. Really smooth idle. Crazy smooth.

However, one more adventure about a month after later -- the MSD coil failed (while on a major SF Bay Area Freeway). It was all very exciting since power steering and brakes also cut out while driving. My mechanic said he's never sent hat happen before. After discussions with MSD, they recommended switching to a MSD Blaster 2 coil, which looks like a conventional coil. I've been driving it everyday for several weeks and I've been really happy with everything.

A final thing that I finally figured out yesterday. After the engine rebuild, the central vent of the AC would not blow. If I manually forced it open, it would blow cold air. The compressor was fine and all other components were fine. Turns out that my mechanic had inadvertently disconnected the vacuum line that connects from the firewall near the battery. It's at the T connector where one end goes to the AC, the other crosses towards the driver side (US) to the vacuum reservoir. The connector missing was also missing the one way valve that then connects to the engine intake vacuum lines (which eventually go to the distributor vacuum connector). The one way valve was missing. I bought a one way valve from O-Reilly that would fit the hoses. And now everything seems to work. I wish I had the original one way valve that jag uses. If anyone has a source, please let me know. Fitting the tubes was a little inelegant. It feels good to figure that one out.

 

DefaultIn response to: "I have read swapping out the ignition does make an improvement. I assume the MSD eliminates the ignition control module? I have a Pertronix distributor and coil to install and am hoping for some improvement as well. I have read where the timing does have to be adjusted."

I had tried the Petronix and ultimately went with MSD. Not sure if it made a difference. My mechanic likes MSD better