Hi
Just completed the London Brighton (UK) rally in my S3 E and noticed
that on a long run like this the tickover increased from its normal
600 to 700 to around 1200 which made the car coast on tickover (its an auto). Anyone have any thoughts as to why this would be? If I drive for about 30 to 40 mins by which time I would have thought the car was fully up to operating temp it stays fine, this was a 4 hours drive though. Its the UK spec engine so has no emission stuff or any USA specific
Cheers
Shaun

Submitted by shaun@paradisi… on Tue, 05/04/2004 - 08:58

Thanks for all the tips!! I'll check the vacuum lines, etc. I don't think its tacho based as you can hear it revving noticably higher wjen hot and the car tends to pull itself along at tickover. Mind you I think my speedo is way out, it bounces a lot and the odometer I think is showing less then it should do as the rally had detailed and accurate stage points.
The rally was organised by the Jaguar Enthusiats Club here in the UK at http://www.jec.org.uk/
Its based on the idea of the Vintage / Veteran road run down annually (and has been for years).
Basically a nice drive out through A and B roads only with two stop off points. First time I've done it (only had the Jag 6 months or so) but will do it agaim, the only poorly organised bit was the start where we waited in a queue for ages and some of the S1 / 2 bolied over, luckily mine never runs hot, new rad, hoses, fresh antifreeze and good fans I guess.

Mind you I noticed in my first post I'd headed it V13, maybe thats why, the extra cylinder is putting it out of balance.

Submitted by jsolo61654@aol.com on Thu, 04/29/2004 - 20:35

Shaun:
I've had quite a bit of trouble with my tachometer as well. First I had to deal with the problem of tach. error and instability due to my Lumenition ignition system. But think I may have straightened that problem out. In any event, I drove the car with my hand-held tach/dwell meter sitting next to me and found that not only is the Smiths tach. off by 50 and sometime 100 rpm - I've also found that the error is not consistant nor linear.
I can also attest to the fact that a vacuum leak, ANY vacuum leak will cause erratic idling and/or high rpm, especially if it's in the throttle by-pass valves located on the right side of the ZS carbs. After re-gasketing my by-pass valves I replaced every single vacuum hose in the engine bay as well as the check valve on the vacuum resevoir. A great tool to use is a simple handheld vacuum pump (available in PEP Boys or any other commercial auto supply) which comes with loads of attachments to fit virtually any hose or fitting you might come across. Simply apply the vacuum with the pump and look for leaks. BTW, once you start replacing hoses, you might consider replacing the hoses that come from the bottom of the brake and clutch fluid resevoirs - the heat in that area seems to eat up those hoses rather easily and it's messy when they start leaking.
Good Luck!
Jeff Solomon

Submitted by cleavefamily@c… on Thu, 04/29/2004 - 15:51

Shaun,
I had a similar, but not identical problem with my S2 E-type w/ automatic transmission. As the day wore on and ambient temperature rose, I noticed that my rpms would increase for the same speed. In the morning 60mph = 3000rpms, in the afternoon 60mph = 3500rpms. To make a long story short it turned out to be the tachometer, and probably had nothing to do with ambient temperature.

Stew Cleave
JOCO Chief Judge
'69 E-Type 2+2 and other LBC's

Submitted by NE52-32043 on Thu, 04/29/2004 - 11:33

Shaun,

Does your car have Zenith Stromberg carbs, with associated vacuum lines, and the by-pass valve on the side? If so, what you're describing can sometimes be associated with the diaphram in the by-pass valve. You can actually blank those off. The temperature compensator can also be a problem if it's not functioning right, but it's influence on the car is so slight that you'd hardly notice it. Should not account for such a huge increase in idle speed.

Also, there is a valve at the rear of the manifold on the A bank (right side). This is used to adjust vacuum as the car warms up. If it's opening, or staying open at high heat, you could be idling high.

You should check and if necessary replace all the vacuum lines on the engine. High idle is often the result of a vacuum leak. With all the heat generated by these big engines, they cook the rubber in no time. You could be opening up a vacuum leak somewhere when things get really hot.

Just a few thoughts.

Steve Weinstein, JTC-NJ
'72 E-type 2+2
'70 XKE FHC