Cold issues

[TurboSE-SLO]

Hi,

Since I have bought my Esprit, she never starts at first attempt when cold, but always on second try. When warm, always starts on first try.

It's not bothering me much, but anyway... if possible, I would like to eliminate "cold second try ghost".

Any idea?

Another "cold ghost": when starts idling OK first 30 sec. After 30 sec. she would like to stall or die for a short time. After that everything is OK, idling and running excellent.

Do I need any ghost busters?

Looking forward,

Borut

[Riddlemr2]

Mine used to do exactly the same thing, and I have heard of others with the same symptoms...it seems like it is just the way some of them behave. Mine used to fail to start 100% of the time, but since I have replaced the fuel pump, plug wires, plugs, and disabled the BPV, it now starts almost all the time but is still occasionally grumpy until it is warmed up. It doesn't seem like anything to be too worried about, just let the car warm up well before driving.

[Artie]

Have you reset the IAC? Sometimes the IAC loses it's position in relation to the ECM and the ECM cannot open or close it properly relative to the engine throttle opening. If you don't have Freescan and a laptop, I suggest you do so as it will be tremendously helpful in all things Esprit!

Artie

[TurboSE-SLO]

Have you reset the IAC? Sometimes the IAC loses it's position in relation to the ECM and the ECM cannot open or close it properly relative to the engine throttle opening. If you don't have Freescan and a laptop, I suggest you do so as it will be tremendously helpful in all things Esprit!

Artie

Hi Artie and Dave,

thanks for answers. An IAC has been reseted several times but this behavior is still here.

Looking forward, Borut

[KENCO]

Have you reset the IAC? Sometimes the IAC loses it's position in relation to the ECM and the ECM cannot open or close it properly relative to the engine throttle opening. If you don't have Freescan and a laptop, I suggest you do so as it will be tremendously helpful in all things Esprit!

Artie

Artie, how do you reset the IAC?

[martynv]

Artie, how do you reset the IAC?

There is an option within the freescan program to reset the IAC, there are also some instructions in the back of the manual as to the procedure for getting the best possible idle. I find on my Esprit that its best to start the engine and let it do its own thing until it warms up a bit, if you try to press the accelerator pedal as it starts up it almost always stalls but seems Ok most times if left to its own devices !.

Martyn

[KENCO]

There is an option within the freescan program to reset the IAC, there are also some instructions in the back of the manual as to the procedure for getting the best possible idle. I find on my Esprit that its best to start the engine and let it do its own thing until it warms up a bit, if you try to press the accelerator pedal as it starts up it almost always stalls but seems Ok most times if left to its own devices !.

Martyn

I don't have the book, can you tell me the procedure for resetting?

[TurboSE-SLO]

I don't have the book, can you tell me the procedure for resetting?

There is a lot going on inside the ECU and a lot of factors are being monitored and adjusted

simultaneously.

The actual procedure when the car first starts is to reduce the IAC slowly down to the lowest

possible setting that maintains the idle speed. The lower the setting, the lower the fuel

requirements, etc. The ECU parks the IAC at 170 counts (fully open air pass) so the car should

not immediately stall when first started. If it does, chances are that the ECU has lost track of

where the IAC "really" is and you will have to hold the throttle open slightly to keep from stalling

out. The ECU "remembers" the location of the IAC at various conditions and relies on this

information to set the valve when things change, like the A/C being turned on.

This learning curve is what the procedure does: make sure the ECU knows where the valve

should be for idle with A/C and no A/C, etc. If it is properly learned, the car should only

momentarily drop rpm when the A/C is turned on, not plummet down to 800rpm or stall out. Once

the "ideal" settings are learned, the ECU makes adjustments "constantly" when the car is idling

(the IAC will move back and forth a few counts) as the ECU tries to keep a steady rpm.

The problem with most of the rough idles is because the GM ECU has a "no load" mode that

alternates the injectors so that only 2 are firing on each full revolution at low rpm and no load. This

can be quite rough on a 4 cylinder engine causing shakes (you're only firing each other piston).

Depending on which EPROM you are using, this mode is entered around 1000rpm. If the IAC

position is not correctly learned, the car can drop well below 1000rpm, go into the "no load" mode,

and then it will stall when the A/C clutch engages! The actual "desired idle" will change based on

the engine load, temperature, fuel, battery voltage, etc. The ECU monitors the rpm and adjusts

the IAC in small increments to keep it around the desired value.

28

FreeScan Manual

IF YOUR THROTTLE STOP IS WRONG then IAC changes will affect the idle to a greater degree

than the ECU expects! The IAC has a dual taper pintle, designed to adjust the air flow in the

correct way for the ECU. If the throttle stop is set wrong, the pintle will be in the wrong place and

the idle will fluctuate up/down more than it should. The dual taper means that the air bypass

amount changes depending on the seating IAC.

The ECU also has a "save me" mode that will jack up the IAC counts and desired idle if the car

idles VERY badly, such as 200rpm variances over 30 seconds. This is similar to the "limp home"

mode and is intended to keep the car running at all costs. If the stop screw is off, or the ECU

learns the IAC counts when the IAC was not reset properly, this mode may come into play if you

find that your car is dropping well below 900rpm, stumbling, then ramping right up to 1200 or

more, this is the cause.

In that case, you need to reset the IAC, reset the ECU and let it relearn the IAC settings again. If

you're crazy enough to want to see the effects, try disconnecting the IAC while the car is idling,

then stop the engine, reconnect the IAC and try restarting the car. The IAC will be completely out

of place (sitting around 20-40 counts or so instead of parked at 170) and the car will likely stall

out right away. If you restart the car, and hold the throttle open slightly for a few seconds and

gently release it, the car will eventually stabilise the idle.

What you're seeing is the constant idle correction of the ECU. The effects of this will be fixed right

after you drive the car over 20mph. The ECU resets the IAC the first time the car is driven at

constant throttle over 20mph.

rgds, b

[KENCO]

Very helpful, thank you!