Occasional engine cut out at idle

[robertverhey]

Hello all I have recently had my SE air conditioning converted to R134a and it’s working well, blowing very cold. However a new intermittent problem has arisen, cut out at idle. Sometimes when approaching red lights and throttling off, the engine just dies. And sometimes when waiting at the lights, it falters and dies. Does not appear to be related to fan or compressor clutch kick in. At all other times it idles smooth as a kitten and the idle “steps up” as it should when the compressor kicks in

Any clues?

[Simon_P]

What you describe happens when you change the idle characteristics but don't reset the ECU - ie the learnt values are the old ones.

Often this will happen if you fix a vac leak or adjust the idle without ECU reset. So check your vac hoses and check the idle (see wiki).you should always check the idle as it highlights if there is a problem that you haven't found.

There are some vac hoses near the a/C ports so check all of them.

The a/c switch commands the ECU to increase the idle speed to deal with the extra load.
With the engine at idle switch the A/C on, you should hear the revs increase slightly then moments later the a/C clutch engage with a click - it shouldn't stumble. It should cycle on (revs pick up click) and off (clutch disengages revs drop) consistently. Edit - just re read and you said this is OK.

Once you have done those checks disconnect the battery to reset the ECU. Go for a drive to learn the new values and your problem should be gone.

[robertverhey]

Thanks for that, I’ll have a good look over it, hopefully it’ll be that easy! I have a retrofitted battery isolater switch that I have (I think) used a couple of times since the aircon was done so I suspect I might have to dig a little deeper to sort this one out. Yes idles fine (when it is idling) and steps up fine when the aircon clutch kicks in. Alas the aircon fella was pretty old school and not really interested in pursuing.

[Simon_P]

The opposite could be true then, and it could be that it is stalling on the reset and needs to learn new settings.

My guess at the root cause is the same though. The idle is controlled by the IAC valve and the only things that influence that are vacuum leaks and setting the idle.

If you can, do an elanscan before making any adjustments, also make a note of the starting position of the idle screw. When you have finished you should see the number of turns indicated in the wiki (1.5?) and IAC position =20 at idle in elanscan

[robertverhey]

Thanks I’ll have a go. The Wiki being referred to is the “tickover” one is that correct? Can’t find any others that relate to idling speed

[Simon_P]

Yes tickover, which is for me at least a far better description.