Questionable dealer suggestion

[Jcarbonbased]

Recently I took my 2002 Esprit to the dealer for scheduled maintainance. The mechanic described something he did to my car and suggested I do the same periodically. He told me to start the car, turn the air conditioner to full and let the car sit in this state for 30 minutes. His reasoning for this was that it "re-teaches" the computer something about maintaining a smooth idil. Does this sound like good advice? Thanks for any help anyone can offer!

[Paul C]

Hi,

Now i don't own a V8, but this sounds like rubbish.

Wrapped up in some truth...

When the battery or the ECU has been disconnected then when the car is started it is in this 'learn mode', finding it's settings.

It is at this time i would need my air-con turned on. This would insure the ECU established idle revs under air-con load.

If i neglected to do this during the 'learning cycle' then the car would learn it's idle without the A/C load and set it as such. Then, at a later date the first time i used the A/C at idle it would be too much for it and i would probably stall.

This is all based on my SE, but i believe it to be about right for the V8 too (someone please put me right if this is incorrect ).

Unless my cars ECU has only recently been reconnected then as far as i'm aware the procedure described will not coax the ECU into setting a desired idle because the learn mode is not running.

I assume

[Bibs]

Are ECU's really so badly programmed that they will stall if you turn the AC on? Surely it will just increase the rpm and then 're-learn' that it has AC for the next time?

[Paul C]

Are ECU's really so badly programmed that they will stall if you turn the AC on? Surely it will just increase the rpm and then 're-learn' that it has AC for the next time?

<{POST_SNAPBACK}>

Yeah, sounds mad Bibs!

but i 'think' thats how it is. The importance of the air-con being on while the ECU is always stressed as part of the learning process, and i thought that the learn mode is not self instigating once set (hence resetting the ECU to clear faults etc).

But i will add again:

I assume

Dermot?

[Paul C]

Can anyone confirm what i've stated here?

(Don't wanna stray onto V8 tech pages and post rubbish )

[Evil_Dr_Fish]

I have just one completely unconstructive word......

Carburettors!

[Jcarbonbased]

Paul C,

Thank you very much for your input. It makes a lot of sense. At least I now know my mechanic isn't completely insane!

Jcarbonbased

[spt350]

Yes, this is exactly what several Lotus mechanics have told me, on how to expedite the ECU on re-learning.

[rocket63]

Well I am no expert. But I have been on the hunt for an SE for bloomin ages. I think I have read just about every published article on the Esprit. I do recall that there is some merit to this. I have definitely read an article that states what you have suggested. No tablets of stone im afraid. I will see if I can relovate the article

[Evil_Dr_Fish]

What Paul C has said is what I recall having read..... The mechanic guy is getting his wires crossed based on a true bit of info...

I would imagine taht the first place to look would be the LEW Modifications page where Kato fitted a new chip and ran through the whole procedure etc....

[Paul C]

Ok...

Just had a look in the V8 Manual.

Firstly, the learning mode is finite like on the 4cyl cars. Driving 'conditions'

determine how long the ECU is in learn mode, but then it finishes, as written here:

iii) After battery re-connection, a change in the engine performance

characteristics may be noted for a period whilst the computer controlled

engine management system Ire-learns' some of its settings. The duration of

this period will depend on driving style, but may be shortened by steady

cruising in 4th gear at about 40 mph.

Then i found..

While it still means your mechanic was talking rot (it would seem ),

It reads here that the V8 ECU deals with the raising of idle revs independent

of the set or 'learned' idle.

EMM.2 - H AIR CONDITIONING & RADIATOR FAN CONTROL

When the air conditioning is switched,on, the ECM receives the signal from the thermistor control unit

requesting operation of the compressor. BefQre energising the a.c. compressor, the ECM first raises the duty

cycle of the idle air control valve to maintain idle speed with the extra loading on the engine. The radiator fans

(3 off) are energised to cool the condenser whenever the compressor is operating. ~

Some engine operating conditions will override the a/c request signal and switch off the air conditioning.

These include: engine speeds below idle to help prevent stalling; wide open throttle to make available full

engine power; near maximum vehicle speed to increase engine cooling system margins.

I assume that the

Some engine operating conditions will override the a/c request signal and

switch off the air conditioning. These include: engine speeds below idle to help

prevent stalling...

is what leads people to stick the AC on while its learning?

HTH

(I'm only trying to help here, and am not a V8 owner, so please check elsewhere )

[neal]

I think this is my first reply on the forum and it's on AC. Bollocks :-)

Anyway, in my experience, the V8 aircon (and I suspect the 4 cylinder) isn't sophisticated enough to make learning such settings much of an improvement.

The idle air control (IAC) valve setting is done using a closed loop system to achieve the target idle speed. So in the non-AC case this ECM learning is important since it can achieve the correct idle speed with less swings making it nice and smooth.

The problem with the AC is that it's not variable - it's either on or off. The knob on the dash is simply a thermostat. So this flicking between AC on (and consequential additional engine load) and off leads to juddery idling. Again the closed loop IAC valve settles this but the ECM learning has less of an effect since the engine load is no longer constant.

One thing I will say about AC is that the best thing you can do is to use periodically during the winter! Like all things Lotus, inactivity is the source of a lot of problems. AC tends to be left alone after September and cranked on full the first hot day in May. Then it breaks! Better to periodically cycle it on full cooling for 10 minutes every month or so (not necessarily with you in the car :-) to circulate the coolant and give the pump, condensor and radiator a nice work out :-)

So I hope my first post has answered a few question.

Of course if you get down to the nitty/gritty, i.e. boost, V8 chargecooling/intercooling/water injection I'll be in like a shot.

Neal

[Paul C]

Cheers neal

His was crying out for a V8 owner to chip in!

[DanR]

I learnt years ago it's better to drive for a period (20-30 minutes) to facilitate the relearning process. The only reason mechanics leave it in idle mode is because they don't have the time to go for drive.

[toyroom]

I have never understood why people turn their air con off ever. Air conditioning is just that, conditioning, not cooling like everybody seems to think. I never turn the air con in my V8 off. In the winter, I simply turn the heater temperature dial to red whilst leaving the air con on minimum. That way, the car is warm (or would be if my heater matrix wasn't blocked), there is no condensation and the atmosphere in the car feels fresh. With the air con off, the car feels stuffy and horrible. Try it ! Just put the air con knob on minimum and the flow knob on feet and control the temperature of the car with the hot/cold knob. This will use very little fuel and will mean that your air con will only need re-gassing once every five years and the car will be much more comfortable. Not to mention quieter as this means you can have the windows shut all the time. It will also mean that the system won't fail every Spring due to lack of use !