I have a problem with my idleness on Volvo S40 1.8L (12/2009). The idle is going up and down and sometimes the engine goes off. I cleaned the throttle but I did;t see any difference..I see no errors inside.

I also found a sensor with the code FOMOCO 7G9N-9P993-AA without any cables connected. What's the purpose of this sensor? How does it work? Any recommendation about the Idle?

 

I'm assuming that the car was idling fine before with the sensor unplugged - or is there a back story we should know about before trying to guess what may be wrong?

That sensor tells the ECU what the thottle body % open is.

 

Hi, Thanks for your reply.

I am supposing you are referring to sensor "FOMOCO 7G9N-9P993-AA" right? I didn't try the idling with this "sensor" unplugged, so I don't know. I just removed the throttle, I cleaned it and I plugged it again. Since this "FOMOCO 7G9N-9P993-AA" sensor does not have any cables, how does it senses the throttle body open %, and how does it inform the ECU? As an electronic engineer, I support, that this can be done almost automatically with the servo motor rotation angle that lies inside the throttle body. Am I wrong?

As you can see from the photo captured from the video link below, it just hangs in the lower-left corner.






The car has only 65.000 Kilometers and has never been repaired before. It looks like the image below. I want also to clear the MAF and IAC valve. I couldn't locate both of them.

 

Your vehicle is very different from US-spec Volvos, apparently. I know that the US spec (2.4l) NA engines do have a plug on the throttle body. I can't imagine a throttle body that doesn't, unless the TB is controlled by a cable and the sensor is located remotely, connected by the cable (like many Hondas).

The US-spec cars have the MAF located in an obvious place on the intake tubing between the air filter box and the TB. But I'm not at all sure about your vehicle.

 

Hi, thanks,

I might gave you the wrong description. The throttle body does have a cable and I fully understand this. The TB is part "B6R25". But, besides the main throttle body that indeed is connected with the ECU, there is an extra component that is hanging at the lower-left corner of the throttle body, specifically the mentioned part "FOMOCO 7G9N-9P993-AA" that has no cables at all. This is the part I have a question about.

In summarizing there are two separated parts a) the main throttle body that is having cabling with ECU and b) a separated part that is attached to the part (a) with the same screws but without any cabling.

Regards,

 

That's part number 30757651 "oscillation damper"

Your engine does not have an air mass meter, only a Map sensor. An IAC or idle control valve is not needed because you have an electronic throttle module. For any running (or most other) problems the first thing I would do is scan the car for any self diagnostic codes - any codes present?

 

Hi, Thanks for the answer.... I suppose this oscillation dumper is working magnetically somehow... What exactly does it? Any Idea?

Yesterday for the 1st time I get the check engine light on :-) I don't have any ODB scanner to check the error code. I suppose I have to visit a tech guy. I am thinking a) opening the throttle body and checking the resistance of the two sensors that feedback the throttle angle back to the ECU b) Spray the contacts to clear them and c) changing the intake vacuum solenoids (they have resistance of about 36Ohms which is a good sign and they seem to work) an especially its hoses Φ3.5.

PS: The picture above is a little different from my engine. As far as I remember there is no map sensor at this location, but I will double check.

 

Volvo uses generic pictures sometimes - your manifold should look closer to the picture below. A scan should be your first step, anything else is just a guess. Here is the US some generic auto parts stores will scan your car for free (hoping to sell you a part or two)

 

When I buy a car, I'll always work out how to get the best diagnostic system available. There are always clones of the factory software available - they're always a little fiddly to get working on a laptop, but well worth the effort. They allow you to drill down into each subsystem, and are an invaluable tool for troubleshooting and maintaining your car.

 

Excellent, I think that's correct. I will check it as soon as I can.

Best Regards,

 

Hi,

I am looking for an ODBII diagnostic system but am a bit confused. I don't care about portability since I have my laptop and I believe that software is always the best solution for quick and cheap updates. But concerning the ODBII scanner interface, I don't know. Is worth buying a $120 scanner like BlueDriver or a cheap ELM327 since this is only the interface and the job is done from the software?

I am thinking about iCarSoft ver 1 ~ $120 or even ver 3 that also I am not sure if version 3 offers something more than version 1.

What do you suggest?

 

I had the VIDA suite, and it REALLY allows you to drill down into the bowels of the car's systems. IIRC (it's been years since I owned one of my Volvos) it required a special interface that wasn't really cheap, but I'm sure there are lots of options out there. I'm sure you can find dozens of threads on it on this - or similar - forums.