Idling Issues

[jthorne]

Hi,

My car (XJS conv 6ltr 1994) seems to be developing a problem and i was wondering if anyone knew what could be the cause....

The idle speed always seems to high. Eg come off the motorway and slip her into N and the revs idle @1500rpm. The only way to stop this is to stop the car and re-start her then the correct 650rpm is immediately found. However move away with some throttle and the problem immediately returns.....

My cruise control also seems to work intermittently, is this related?

My MPG is also high, c 12-13....

Any ideas very gratefully received!!!!

Many thanks

Jon

[dhdove]

Jon

I'm pretty sure that your idle speed valve is on the way out. Tho the system on the V12 is different from that on the 4.0 litre your symptoms match those that I had exactly.


I would advise you to get this fixed pdq as it could get worse and worse to the point that it is downright dangerous - try controlling the car when the revs wont drop below 3000rpm! (see my post in Engine section - "AJ16 Drives Itself!").

Also See Here

http://www.jaguarclassicparts.com/webap ... gory=21099


I don't think "intermittent" cruise problem would be linked to this but high fuel consumption may well be as the ecu will put in more fuel to try to retain the mixture ratio at the correct level - I guess this is why the rpm gets higher and higher.........

Best Wishes

DH Dove

[ptjs1]

Jon,

Give Dave Marks a ring or email. He's the JEC Technical support. I suspect he'll give you answer (or possibilities) straight away.

Intermittent cruise problems: I would start by looking at the vacuum bellows. They are very prone to leaking around the flanges. Simple to fix with silicone sealant if that's the problem.

Good luck

Paul

[dhdove]

Paul

Sorry, only offering some advice based on my own experience.
Of course it is wise to explore all other possibilities before committing to a course of action.

NB Can you carry out the old "silicone round the bellows trick" on the (later 5.3 and 6.0 ltr) Kiekert cruise control system?

Regards

Dh Dove

[jthorne]

Thanks for all this!

I have check all the pipes/bellows etc and seen no problem so have found a new/SH cruise ECU unit. (Do you know where it goes?) As for the idle i will mail David Marks but in the meantime have had my eye out for a new air valve just in case....

Many thanks again

Jon

[ptjs1]

dh,

Don't apologise, I think one of the real benefits of the Bulletin Board is the ability to seek a broad range of views from members who may have a view. My suggestion to ring Dave M was merely a way of saying "I don't know the answer, but I know a man who might"! As you know, I had a similar idling problem on my 4 litre which proved to the ususal throttle body carbon build-up, but I don't think the V12s suffer from the same issue.

As regards the cruise on the late cars, it's the same actuator bellows on the late 5.3s & 6.0s. You wouldn't really expect a 94 car to suffer from a bellows sealing problem, but I guess it's an easy place to have a look first. I've got a cruise problem on my Range Rover at the moment. It started off working intermittently and has now given up the ghost completely. I've checked all the vacuum issues, so my next guess is maybe a dry joint in the cruise ecu.

Paul

[dhdove]

Paul

None taken

"it's the same actuator bellows on the late 5.3s & 6.0s."

- that'll be the Kiekert cruise control system then........ I thought the design of the vacuum housing precluded (and negated) "the old silicone around the bellows trick" ( but to be honest I'm working from memory from what Dave Marks said!).

Sorry to hear the Range Rover is poorly, please can you repair it before next spares day, just in case. NB have you tried a brick against the accellerator???

V Best Wishes

DH Dove

[davidchevin]

You could try looking for cracked or worn vacuum hoses. I had a 'fast idle' problem that was cured by simply replacing a split hose (from one of the airboxes to a y-shaped metal pipe thing, as far as I remember). This might also, I suppose, affect the cruise control if it gets mixed signals about vacuum?

[jthorne]

Spent the day "fettling":

-Cleaned all the metal vacuum connectors (they were quite fouled up) and re-sealed the hoses, idle speed eventually now down to 750rpm!! However it still takes it's time to get there after use, is that normal? Very pleased as even when on "high" it's only 1000rpm now.

-Took up passenger carpet to change cruise ECU, changed it over but realised that everything was wet! Dried it all off and now cruise works perfectly.

-Investigated water ingress, removed carpet and foam for drying. Re-sealed wing mirror to door, now watertight. Found wing mirror wiring disconnected, replaced and now for the first time in ownership i have functioning passenger door wing mirror!

-Reconnected heated rear window wire with new connector, now working.

-Pressure tested A/C, found to be low (15psi) even after new reciver/dryer, compressor, pressure switch. Added gas to 35psi will re-check after a drive tomorrow but for the moment now v cold.

-Investigated non-running "other" car, found faulty coil ordered a new one.


-Home for a nice cuppa!

[dhdove]

Jon

Sounds like a good days work- Result

Re idle speed - it's not something as simple as lube needed to throttle body,cables, pedal etc.? ie it's a bit sticky?

Regards

DH Dove

[poprivet]

Pressure tested A/C, found to be low (15psi) even after new reciver/dryer, compressor, pressure switch. Added gas to 35psi

Which gas, also Dynamic or Static pressures? As you may know, refrigerant gas pressure relates to the temperature, not the volume.
If its working though, that's great
Pop

[jthorne]

SODS LAW!!!!!!!!!!!!!!


Coming back home today from work my car blew a flipping coolant hose!!!!!!!

It's the one that comes off a T piece just in front of the drivers baulkhead and then goes to what looks like a valve of some sort just above the D/S manifold, its only 6-7" long and shaped like an upside down walking stick. Does anyone know the part number or know where i could get one as the AA just patched me up to get me home.....

Sods flipping law, she ran beautifully to Cardiff and back yesterday!

[ptjs1]

Jon,

Can you post a photo of the pipe in situ?

Paul

[davidchevin]

You may see it here or on an adjacent page

[ptjs1]

David,

I had looked at that page but presumed it wouldn't be any of those as Jon had mentioned a coolant hose rather than an aircon hose.

Paul