Hi all - new guy here.

I have a 1999 S40 which has developed over the last couple of days an annoying idle problem. Today it got so bad that everytime I stopped, the car stalled. RPM speed does vary but car usually sits around 450/550 RPM. Lately its been jumping from 200 up to 1000 and it gets worse when I brake.

Have had this problem before and the main dealer replaced the idle contol valve and it also looks as if they did some 'jerry-rigging' around the idle contol valve to bring the idle speed up. Had a mechanic look at the car tonight and he was stumped - he has a V40 from the same time so we took bits of his car to try to identify the fault. Guess what, we couldn't. We swapped the idle contol valves over - didn't make any difference. We basically swapped everything from the V40 that could have an effect on the idle speed but end result was still the same.

Has anyone ever experienced problems with the idle speed in a S40 and if so, any ideas on how to resolve it? I'm kind of worried it's an ECU issue and that'll cost a fortune!!

mine did that when i reduced the air flow meter on the airbox. it set the ecu onto fault 'go home safely' mode too. have you checked the airbox? it could be an ecu problem.

Yeah i had the exact same problem with my 1998 T4.
First of all the ECU light was on and off for a few weeks, then it was on perminant and thats when it started stalling when idle.
Took it to volvo for a diagnostic which they did, and they wanted just under £500! to fix it, no thank you!
Explained the problem to a mate who is a mechanic and he reccomend an engine managment specialist not too far from me. Took it there and he ran a diagnostic and found the problem straight away. I have keept all the paperwork from the diagnostic so if you want the results just send me a message and i will e-mail them to you.
He fixed the ECU problem along with some other things and it was still alot cheaper than what volvo wanted, which by the way havn't got back to me about it.
All in all the total cost was £284.55

It is a different car to drive now! well happy! :grin:

Did the mechanic also clean the throttle body? a dirty throttle body can cause erratic idling.

Hope you get it sorted.

BB
:57:

Yep he cleaned it and changed something aswell, dont know what it is, hav'nt a clue about cars. He did a bang up job.

:banana: :beer: :banana:

When the idle speed went crazy on my T4, Volvo cleaned the throttle body & idle motor and tried to download some updated software onto the ECU. ECU crashed & died, so had to be replaced & loaded with up-to-date software. Hasn't missed a beat in 6 months since then. :amen:

BB
:beer:

you like cleaning throttle bodies. i've just noticed in most of the posts i've looked in you usually say 'clean the throttle body'. i think i'll clean mine. :grin:

... as recommended every 20,000 miles by Volvo technicians & it cured the erratic idle problem on my T4 so yes, I'm converted!

BB
:haha:

Please tell me were to find the throttle bottle and the Idle Motor on my volvo s40 engine I would like to clean the same.

I have exactly same problem.
My car right now is at Volvo Dealer.
I believe that the problem comes of the Fuel Pressure Regulator.
I hope it will not be such expensive to fix it.