03 S40 weird problems

1812paul · Post by **1812paul** » 02 Feb 2021, 04:13

So initial start everything seems fine. After it warms up heater will stay on and not shut off, it idles at 2grand when in drive but when I put it in park it throttles up and would redline if I didn't shut it off. Also radiator fan will come on and stay on? Help.....It did sit for a year with a broken alternator bolt. I bought it and fixed that. Got it running and this is what it does now. Previous owner says that it didn't do this before.

Volvoblackdog · Post by **Volvoblackdog** » 02 Feb 2021, 14:01

I had a similar problem with my '01 S40 and it was my O2 sensors. I just took them both out and blew them with compressed air and carb cleaner re installed and worked fine after that. Are you getting a check engine light? if so, download and see what code you are getting. If you dont have a reader go to a Auto supply store and either get one or have them do it for free (usually) . They will more than likely tell you its your O2 sensor. There are some other things it could be of course but this is the most common. Another item you might look at is the Idler valve, I have had this problem but usually it will not idle at all and will usually be a low RPM idle or stall. That doesn't mean that this is not your problem either. Good luck!

1812paul · Post by **1812paul** » 04 Feb 2021, 07:40

Thank you I will check today and let you know.

Volvoblackdog · Post by **Volvoblackdog** » 04 Feb 2021, 09:37

Okay let me know if it helps. I may be on the wrong track but if it helps I want to know. Just to let you know I am not a professional, shade tree mechanic. Thanks