high tickover

2.7 V6 30v biturbo - 251bhp
2.7 V6 30v biturbo - 261bhp
1z
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high tickover

Post by 1z » Thu Sep 08, 2005 6:48 pm

not sure what the tickover speed should be on a 1999 s4, but i am noticing that mine feels a little high idling at 800 rmp ,
on choke at about 1200 the revs seem to take a long time to drop espesialy when changing gear a bit like some v6 vauxhauls used to be, is this just how they are ? or whould you say i have a problem, its making the car hard to do a quick change without the revs dropping i always thought i had a problem with the revs not dropping quickly enough, but i have just hade a custom duel exhaust system made today and can really notice somethings not right ,
ps the custom duel system i had made sounds amazing and a work of art

will be putting 710n diverter valves on next week ,would a leaking dv cause the problem,i tried to do the usuell d/v check, will need to get the new ones first, them pipe clips look fun

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Post by S4INT » Thu Sep 08, 2005 8:53 pm

Would say that your idle speed sounds right - mines the same, but my revs die away quite quickly (not like Vauxhall) Don't know what would cause that though? Get your fault codes read.
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dazzer
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Post by dazzer » Thu Sep 08, 2005 10:01 pm

Mine's the same as S4INT.

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dazzer
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Post by dazzer » Thu Sep 08, 2005 10:04 pm

Mine's the same as S4INT.

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Post by 1z » Thu Sep 08, 2005 11:16 pm

just been reading about the clutch pedal switch
could this be my problem?
seems to show all the signs exect putting any light on




http://www.funkadelic.org/gallery/clutc ... adjustment

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Post by UKS4APR1 » Fri Sep 16, 2005 12:10 am

Clutch switch has nothing to do with actual tickover. With cruise control it has a function and without cruise control it also operates a valve of some sort I believe for dropping the revs when changing gear.
In other words....I had the same problem of revs not dropping quick enough when changing gear when I first got my S4. Clutch pedal switch was doing nothing (i.e. not touching the pedal!) Adjusted it and all was fine, revs drop when changing gear. As the link shows I logged the function of the switch with Vag-Com to prove it was working.

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Post by 1z » Fri Sep 16, 2005 9:39 pm

looks like it is the clutch switch then,
you have described you problem and mine is exactly the same revs wont drop off quick when changing gear.
was yours worse when the cars on choke? i had a quick look for the switch today, how do i get to it ?
can i just adjust it, or do i need the vag to set it?
i have no cruse control

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Post by UKS4APR1 » Fri Sep 16, 2005 10:12 pm

Easy to adjust, it's a simple switch pushing down on top of the clutch pedal with thread and nuts either side to move it up and down. Mine was not even touching the pedal when I first looked at/found it. You have to remove the "shelf panel" complete to get at it (about 4 or 5 8mm hex head screws - look for them) it's the panel below the 'carbon fibre' strip below the steering wheel. You need to remove the fuse panel cover off the end of your dash, there's a couple of screws under there (just pulls off).
It's easy, just a little awkward contorting yourself to get at it.You don't need Vag-Com to set it, it is just a switch on/off when you operate the clutch pedal.
My tickover on "choke" as you call it is about 1200 revs for a very short time. With the clutch switch not working I remember the revs actually went up between fast gearchanges and I hated it.

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Post by 1z » Fri Sep 16, 2005 10:50 pm

Nice one! you have saved me hours of fumbling, this sounds like a guaranteed fix for me as well exactly the same problems will keep you updated

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Post by UKS4APR1 » Sun Sep 18, 2005 12:58 am

Just copied/pasted from Bentley manual for you, this is the switch we are talking about.......


Clutch Vacuum Vent Valve Switch -F36-, checking

Note:

This signal is used to avoid RPM over-oscillation and load change impacts when changing gears and is also used for the cruise control system.

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Post by eddiecrawford » Tue Sep 20, 2005 8:48 pm

might be an easier way to check clutch switch, if you have a boost guage

engine warm and idling, push clutch pedal down/release etc a few times. inlet manifold vacumn decreases a bit with clutch disengaged(pedal to floor)

not very useful really, but at least i think mine is working...... :)

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Post by UKS4APR1 » Thu Sep 22, 2005 10:55 pm

Nice idea eddiecrawford, you may well be right, however just wondered if pressing the clutch at idle and hence removing the slight load of spinning the gearbox idler shaft and gears through the oil and inertia of the clutch plates might also cause the vacuum to decrease slightly.
If you load-up your alternator by switching on your headlights or switch on the air-con, the reverse effect will occur.
I think the clutch vent valve is something to do with the servo brakes, a turbo car under boost would cause the servo not to work / work against you so a system is in place to account for this. A brake servo is activated by vacuum from the inlet manifold in the 'normal' fashion. Diesel engines have a similar problem and have to use a pump to generate the vacuum.

Isn't it easy to get bogged down on the most simple thing!
I seem to recall I got a fault code on Vag-Com which led me to inspect my clutch switch. When I looked at it, it was not even touching the pedal.

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Post by eddiecrawford » Fri Sep 23, 2005 8:59 am

thought of an even easier way, if you have cruise, it disengages when you hit the clutch... ie there is a switch. doh!

wondered about load of input shaft etc, but (on mine) switch activates almost as soon as pedal starts being pushed, ie clutch still engaged. also you would expect vacumn to be less for more load, not less when you disengage the clutch

yes when you put on a/c etc, vacumn is less

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Post by UKS4APR1 » Fri Sep 23, 2005 10:24 pm

Gets a bit confusing doesn't it, less vacuum is more!
More vacuum is a higher negative reading i.e more is less.
Same as zero on boost gauge actually means you have boost, otherwise you would have vacuum or engine not running.
I always wondered how much boost 1 bar is (approx 14psi) as that is 1 bar above zero, but in reality you are boosting from a negative amount?
Anyway there's a chap with a white coat at the door holding a hook, say's he's from an institution - better go see what he wants!

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Post by eddiecrawford » Sun Sep 25, 2005 10:43 pm

it gets worse;

"zero" on a guage is not zero at all, its zero (guage) or 1 bar absolute

atmospheric pressure is one bar. this is what our boost guages read as zero (!) ie when your boost guage reads 1 bar, its 2 bar absolute, or 1 bar guage. hmmm.

the way i remember it, space is near enough zero pressure (absolute), where we are at the bottom of earths atmosphere, its one atmosphere=one bar. if we have turbos we can add to that...

am i even spelling guage right???

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