S40 erratic idle and stalling after flat battery

[Milloni99]

Hi - I went away for hols for a week only to return to find a dead battery from my son having left a cabin light on for the week (I suspect). It is a 2003 GDI S40.

Anyway, battery recharged and is holding a good charge well.

However, car now has an erratic idle and keeps stalling whenever the foot is off the gas. The idle is like a roller coast between 500 rpm and 2000rpm. I think it used to sit happily at 1000rpm but whenever it hits 500 now it dies. Pretty dangerous if changing gear halfway through a corner and you lose power steering!!!

Having read the forums, it suggests this can be a mechanical issue e.g air filter, throttle body cleaning, idle adjustment, etc. However, the car was running perfectly beforehand so I am more inclined to think this because of an ECU reset from the dead battery.

One thread says that the car needs to re-learn the values for the idle to stabilise.

But one week one, and it s still occurring. Am starting to think my only option is to take into a Volvo dealer but I am reluctant to incur cost as about to sell and think I wil easily get hit for mechanical bits which I really don't think are the issue. Again, it was running perfectly fine before the dead artery.

Any thoughts most welcomed please.
Thanks,
Simon

[gatos]

Flat battery, has reset the ECU and your car needs to re-learn. Most probably, the engine is coked up and the ECU was compensating in throttle position, fuel/air mixture ratio. Now that these values are reset, car will struggle to idle

The following text was copied from here: http://www.volvoforums.org.uk/showthread.php?t=87173

Thanks to all those who posted here for putting me on the right track, still needed a bit of trial and error plus Haynes (as bongo says it's in section 'ref 5'), the full process is:
1. Disconnect battery, short battery leads together (don't short the battery ), turn on ignition, and leave for 15 minutes.
2. Disconnect short, turn off ignition, and reconnect battery
3. Start engine and leave to idle WITHOUT TOUCHING THE THROTTLE until engine is FULLY warmed up (bits in capitals are bits I found out the hard way!!). This took 25 minutes in my case. If it stalls during this stage just restart it.
4. Run at 1200rpm for two minutes.
5. Drive 'in varying conditions' for five miles.



If this fails, you will then have to remove the inlet manifold and clean all the coking up there, as well as on the throttle body and the EGR valve. Once you do that, repeat the steps to reset the ECU and hope that your car will idle correctly.

[Milloni99]

Thanks gators. Have just tried that ECU resetting exercise but to no avail. Have just put a new air filter in as a precautionary measure too.

Might sound like a silly question, but is there not just an idle adjuster somewhere that I can play with to get the right tickover?

Otherwise Looks like next step is to clean the carb. I found a promising thread on here with step by step photos on how to do this but unfortunately the links seem to be broken.

Don't suppose anyone else out there has any photos on how to locate the throttle body let alone do it?

Thanks as always

[gatos]

here you go:

[Milloni99]

Champion - thanks. That's this weekend's plans sorted then

[Milloni99]

So wasn't too sure on how to easily get to EGR valve and was reluctant to take throttle body off to get to inlet manifold so did the easy things of cleaning throttle body in situ with carb cleaner, changing air filter, cleaning air intake hose and putting some FedEx in the tank.

Immediate difference and so far so good. Am touching wood for now as imagine it needs some time to bed in and recalibrate but fingers crossed it might have done enough.

So many thanks for now gatos.

[stuartpratlett]

I seem to have this idle problem after fitting a new battery this morning, AA fitted it at my house. Started stalling at junctions etc, phoned the AA again, he came back but was completely flumuxed!! Showed him the ECU reset post and he advised me against doing it. When you say the car needs to re-learn, does that mean it will eventually correct itself or is the ECU reset a must??

There is very little info on this anywhere, is it just a ploy to extract more money out of you at the dealer!!

[gatos]

Most probably your EGR valve is clogged completely and your inlet manifold is coked up. This is a typical occurence on the infamous GDI. Your ECU would have to adapt the air/fuel mixture as well as some other parameters to compensate for the blocked bits. You have inadvertently reset your ECU by replacing the battery. So I am not sure why the AA man has advised against this...........

COntinue driving the car for a few days and hopefully the car will learn the correct settings and you will be good to go. If it does not work, then I would suggest you follow those steps I have mentioned above to reset the ECU and see if that makes a difference

[stuartpratlett]

Thanks Gatos. Will see how it runs until the weekend.

[blairs40]

as far as just a ploy ...... I know its not a Volvo but late model Mitsubishi diamantes are similer ..... when you put a new batt in make sure everything is turned off and the drivers window is down already , new batt in ,,, start her up and don't open the door or anything , just walk away for at least 20 mins .... then turn off , and then do the driving thing using various speeds ......the more modern we get the crazier **** becomes