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Idle Control on V8


superdavelotus

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Can you adjust the idle on a V8 either manually or electronically?

If so, please give details.

I know the air idle control valve needs to learn via the ECU if it's been off or the plenum has been off.

Regards,

Dave Walters

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Hi Dave,

There is nothing to adjust ! Please donot mess around with the butterflies !

The IAC valve is exclusively controlled via ECM and will control the idle perfectly to around 980 rpm when the car is stationary.

If the car moves (>3 kph) it will be just above 1000 rpm.

If you have the Tech1 then you can monitor the IAC duty cycle. It will vary somewhere between 35-100%. If it is fully shut it will be near 35% and if it is fully open it will show near 100%.

The reality is somewhere inbetween.

If you actually have a problem with the idle (or with the engine dying) then you just need to relearn the idle properly.

Easiest way to do this is going on a loooong run. Whenever you come to a stop and the engine dies just let it die and restart it (without pressing the throttle !!!). Sooner or later the ECM will have relearned the idle.

BTW, dont forget to do this also with the A/C ON.

Cheers

Marcus

Marcus

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Thanks Marcus,

It looks like I need to go for long drive!

I just haven't had chance to drive it since yesterday when it came out of the garage.

Will let you know if it sorts itself out.

Dave Walters

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Perhaps that a drive to Norwich then Dave?

Are you joining the NMEG boys at Norton canes on Saturday?

See you soon,

Graham

Wing Commander Dibble DFC<br /><br />
North Midlands Esprit Group<br /><br />
NMEG "the formidable squadron"<br /><br />
"probably the most active Esprit group in the world" Andy Betts, Castle Combe May 2007

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Hi Graham,

Not 100% sure Iam going yet, need to work out a few things yet.

Iam planning a trip in my daily car to get the parts in. Iam also driving down early hours of the morning.

Dave

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The IAC valve is exclusively controlled via ECM and will control the idle perfectly to around 980 rpm when the car is stationary.

If the car moves (>3 kph) it will be just above 1000 rpm.

Quick question, Marcus. Page 47 of the Owner's Manual states that "the normal idle is about 850", and that following use of the throttle above idle the RPM will remain at 1100 for 20 seconds, and then slowly "decay" to 850. This is in fact what my car does (at rest, anyway). I know that you have been at this for a lot longer time than I have, and are much more "up to speed" (pun, intended) than me on all things Esprit (I still grin each time I open either door and catch sight of the Lotus graphics door sills that I purchased from you several months back), so I am wondering where you found the 980 figure. Not trying to be argumentative, just truly curious. :D

Cheers,

John

Being second is to be the first of the ones who lose.

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Thanks for the clarification, Marcus.

So does this mean that if one of my cam timing belts self destructs (turning me into an "instant 4 cylinder model"), that my idle will increase to 980 to compensate?

Just kidding. :)

Cheers,

John

Being second is to be the first of the ones who lose.

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Poor Gunter. I have followed his saga, and must give him great credit for maintaining his sense of humour about the whole affair. I would be a "basket case"!

Being second is to be the first of the ones who lose.

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  • 3 years later...

following on from this interesting read i have been looking at a v8 to buy the guy said the idle control valve is faulty and that he had the spare part it just needed fitting so if this is the case or does it just need to re learn its procedure again if it needs changing is it a long job where is it located any pics from technical bods many thanks alex

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The high / slow decay idle drove me nuts on my V8. So I now have modified it so I get a perfect idle straight away, which also improves the gearchange as the revs drop very quickly.

The geezer from Lotus I spoke with today while testing an Exige S reckoned it was a "very intelligent" modification. Praise indeed!

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Aaw Kaay Graphhopper, today we rearn abaout Effprit Idle contwol.

Ermm.

Right listen up. Very easy. It's is a case of fitting a second thermostaticaly controlled idle valve. That is open from cold, so the original works as usual, then at around 40deg the second valve closes to the default idle position. Hey presto, proper idle.

Also, fitting proper rod ends to the gearchange cables. That also helps to sort the gearchange.

Drove an Exige S yesterday and the gearchange is little different to mine.

The Exige was very good, very refined. But no Drama! That is what you get with an Esprit. James from Lotus agrees!

I can assemble a kit to supply or even supply and fit in my workshop.

There, fully declassified!

The Exige was very good, very refined. But no Drama! That is what you get with an Esprit. James from Lotus agrees!

Drama - the sound, the feel, the look........

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^ That's about 10 levels above my automotive pay grade :huh:

88 Esprit NA, 89 Esprit Turbo SE, Evora, Evora S, Evora IPS, Evora S IPS, Evora S IPS SR, Evora 400, Elise S1, Elise S1 111s, Evora GT410 Sport

Evora NA

For forum issues, please contact the Moderators. I will aim to respond to emails/PM's Mon-Fri 9-6 GMT. 

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Well done Paul, its good to see people like yourself thinking and working out ways to improve our Esprits. I agree if the V8 appeals to you there is very little that comes close as a complete package as I recently found when I had (sold) mine driving back from test driving an Aston Martin DB9 V12, a 360 Modena and a 911 Turbo S I concluded that despite being twice the price none except for perhaps the Turbo S were twice as good.

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I'm intrigued Paul.

When you say a second IAC valve do you mean you have the two operating in parallel?

If so how do you prevent the original IAC from opening under the control of the ECU?

I was looking at just a clutch operated switch that would disconnect the PWM control circuit from the original IAC for gearchanges. The IAC would then be left to control warm up, aircon settings etc as before. The ECU would only loose the ability to hold the revs up during changes.

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No.

The two valves are in series. When cold the aux one is open and the original operates as per stock. When warm the aux one closes to its default closed position to give a 900/1000 rpm tickover - regardless of what the original one is doing.

Will put together a price for a kit to do this for those who are interested.

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