S40: 2002 S40 1.8 petrol automatic stalling after starting

[Ltom]

Hi everyone, I'm having bit of trouble diagnosing this stalling problem. Sometimes (but not always) after starting the idle drops low then stalls immediately. If it happens once it will keep happening. To get it to start I have to use the throttle to keep the revs up for about 30 seconds then slowly lift off. Hasn't stalled at a traffic light yet but seems to be getting worse. Idle seems a bit low to me around 200-400rpm.

Things I've tried:
• Cleaning the throttle body and idle control valve, they weren't that dirty. I also cleaned all the electrical contacts related, no difference.
• Following the reset procedure for the ECU. It didn't stall when I started after disconnecting the batteries, but after the 5 mile drive I stopped and tried again and it stalled straight away.

Does anyone know what could be causing it? I also noticed that the gear changes are a bit rough sometimes but this could be unrelated.

[Ltom]

As an update the idle control valve seems to be working and the throttle position sensor has sensible resistance changes between 0-90°.

After a few failed starts the electric engine fan came on even though the engine is completely cold and it's about 10°C. The engine temperature sensor in the dash cluster works fine.

From reading other posts it seems MAF sensor failure could be a culprit. Are there any diagnostics I can do?

[gatos]

Ideally, have your codes read to see if something comes up. Also, you can unplug the MAF and see if the car runs ok. Also, is it possible that someone has played around with the throttle cable? You could adjust it and try to get slightly higher revs and see what happens.

[Ltom]

Thanks for the reply gatos. I'll go and have the codes read and see what comes up.

I unplugged the MAF but it still stalled immediately after starting.

The throttle is completely closed when idling, I assume this is normal? Otherwise the tension and adjustment screw haven't been touched and look normal to me.

[mrfixer]

You could try a new fuel filter maybe low fuel pressure

[Ltom]

Does the 1.8 have a serviceable fuel filter? Or is it inside the fuel tank?

Edit: I've just had a look underneath and it does, I've ordered a replacement filter and we'll see if that helps. I'll get the codes read too.

[Ltom]

Okay I changed the fuel and air filter - no improvement.

I had the codes read and lots flagged but probably from me unplugging and cleaning. Cleared the codes, started and stalled again, no codes flagged.

Suspect #1 is the MAF sensor, I'll try a generic one tomorrow and see if that changes anything.

Suspect #2 is the temperature sensor. Does anyone know standard readings for the temperature sensor so that I can check it with a multimeter?

[Ltom]

Okay new MAF did nothing, still stalled immediately. Do I need to do a reset procedure or anything after fitting?

This is starting to be a right pain. Any suggestions or advice welcome.

Edit: Suspect #3 could be fuel pressure regulator?

[Ltom]

Fuel pressure regulator is not leaking petrol so I think the diaphragm is okay.
I replaced the spark plugs but the old ones looked fine and there was no improvement.

Does anybody have any suggestions? I feel like this shouldn't be that hard to get to the bottom of!

[gatos]

Have you tried adjusting the throttle cable, so the car can rev at 800? Maybe a bit higher when it is cold