Hi again,
I spent some time messing about with the car again today. I reconnected the wide open throttle switch today and in general it seemed to not do much while idling (I guess thats the point) any how, while I was fiddling about the car just died. Now this has been one of the issues I have been chasing for some time but have never had it die while idling in the garage. So I started wriggling wires and then I could hear the injectors clicking away while moving the white bullet connector wire along the top on the manifold. I had replaced the female bullet connector some time ago and the plastic sleeve on the connector had shrunk at the opening from the heat and basically pushed the connector apart enough that the joint became intermittent. Replaced it temporarily until I can find a connector that won't be affected by the heat. The car started up ok but then started cycling. The idle was up around 1400 RPM and then drops momentarily to about 900RPM then back up again. The car was also hard to start without accelerator input. The car had always been a foot off starter. So not sure what has changed. I did disconnect the wide open throttle switch just to be sure this wasn't messing with things but still the same. This has all happened as the car has reached normal operating temp. I have done the cap mod on the connector to the AFM but was unsure what type of capacitor to use so used an electrolytic capacitor was this a good or bad choice? Can any one tell me if this could be my problem? If not the cause does anyone have any thoughts on where I should be looking?
Thanks
Con

 

First, to clarify, did this idle speed problem occur only after the cap mod was done?

Anyhow.....

I came across the up-down idle problem many years ago on a Series III 4.2 but I can't remember all the gruesome details.

At some point I decided to clean the throttle body and air distribution valve, reset the throttle blade gap to to .002", and then reset the idle speed.

That fixed the problem. I can't remember why it fixed the problem or what took me down that path to begin with

Also, just on general principles, make sure the ducting between the throttle body and the air flow meter is leak free

Cheers
DD

 

Second the check for air leaks advice and forgotten little pipes
You can use a can of brake cleaner to spray around the area to see if that affects the idle and help track it down

 

Hi Doug
The cap mod had been done by a PO. I did replace the cap as the old one was kaput as measured on my multimeter. I have not had this problem for sometime but last time it was due to crap in the fuel tanks which was so bad that it actually slowed down so much that the motor stopped. occasionally. This is different. I think a proper clean and reset as you have done may be called for.
Con

 

Doug,
Just so I am clear the "air distribution valve " is the same as the Auxillary Air Valve?. If not where can I find it?
Con

 

Not the same as the AAV

Is a small aluminum casting on the intake manifold 3-4" forward of the throttle body. Two vacuum hoses, one large, one small. Order a new gasket before removing; the old one might not survive. There's a spring device inside (the over-run valve) make sure to note how it is oriented so you don't reinstall it upside down. The idle speed adjustment screw is in the air distribution block.

The air passage for the idle speed adjustment may be gunked up, preventing the adjustment from having any effect. Clean the whole assembly.

Cheers
DD

 

Thanks Doug on the to do list
Con

 

OK now I need to know where I can get the gasket for the Air Distribution Valve in Adelaide, South Australia. According to the Parts manual it is part of the Head Gasket Set. Do I just go to Jaguar themselves or does someone here sell them separately? Not sure if anyone knows? What type of gasket is it? Can I make one myself? or use a liquid gasket type material instead?
Con

 

The gasket is part number EAC1743 but you can make one yourself, yes. There's nothing exotic about it

Cheers
DD

 

My belated two bits!!
A 900 to1400 rpm swing seems like a decided engine 'lope". An old tech term for an engine with a long duration cam timing or merely too rich. In your case, it sounds rich. Further suggestion is that adding throttle, ie air makes it better.

Now, others are far more familiar with what controls mixture than I, I will defer to them.

Might even be covered already...

Carl

 

Thanks Carl
I have long suspected that this car is running rich but do not have the correct tools /meters or confidence to set up the mixture correctly. I have a longish list of things for my mechanic but every time I have the money to spend with him life gets in the way, I am also thinking that part of my problem is the wiring. I will spend some time checking the wires from that big white connector near the firewall. I drove it a bit yesterday and it was ok but conked out as I went around a corner and then I had a hard start but wriggling that connector seemed to get it going again. What a pain.
Con