Ok I have an S40 that should be able to obtain about 30mpg or really close to that, how ever after I don't think it's getting any where that, so I need some help solving the issue, my issue it the following, when I turn it on it some times takes a few seconds to start up, also the service light remains light for a while until the car gets relatively warmed up, however there are NO codes stored in the computer, when it had some it was a code for the exhaust can shaft sevearly retarded, but I cleared that and the codes have not come back.


I do know there is some sort of issue with the Tstat where I think it stays open at all times, not sure if that is causing the issue but I plan to either replace it my self or have it done, replacement will be a super stat .


Anyways any help you all could provide would be appreciated!




Jim

 

What year and engine? There is a big difference between the 2000-2004 and the 2004.5 + models. On my 2005 S40 the service light illuminates to remind you that an oil change is due. It goes out after 15 seconds. It will continue to do this until I reset the light.

If the t-stat is stuck open then fuel mileage will decrease as the computer adds fuel attempting to warm up the engine. How exactly do you know the t-stat is stuck open?

The usual suspect for bad gas mileage is a worn out oxygen sensor. They should be changed at 100k miles at the latest. Have you changed yours?

 

As for the oxy sensor, not sure I don't have any Maintenance history on this car so I'm assumeig no it has not been changed, as for the Tstat sig other said that te car had that issue going on for a while, which was what I suspected was causing the service light, I did reset the light and it still comes on, and it stays on until the engine gets warmed up to operating temp.

As for the year I'm not 100% sure sig other thinks it is a 2002 built car but marketed as a 2003 year model date on the vin tag reads 12/01

 

The service light only means service is required. It comes on at 7500 miles. It does not indicate something is wrong. That is the check engine light. It comes on when a trouble code is set in the ECM.

I asked about the tstat because you said "when the car warms up" which indicates the tstat is working. Normally a stuck open tstat will not allow the engine to warm up as indicated by the coolant temp gauge on the dash.

2001-2002-2003 are pretty much the same so you are set there.

 

Ok how do I shut it off, it's a bit annoying not knowing what needs service. We do take the car for oil changes and all that regularly, it's got about 90k on it

 

Reset service light:
-with the key in the off position, push down and hold the odometer button.
-turn the ignition on (all the lights will come on).
-hold the odometer button down until the service light starts flashing.
-release the odometer button while service light flashing.

 

The S40 weighs @ 3200 lbs. You cant expect to ever get 30mpg, even on the highway.

 

Ok, well it was advertised around close to that IIRC but that's not a big deal 25 mpg to me would be great, it's just that I'm having the fuel drop from full to half way after about 1 hour at 70 and I've seen other similar year volvos get better mpg then what I seem to be getting, hence why I think something may be causing this, but I will defer to you guys as the experts.

 

It's possible. EPA says 20 city / 29 highway. This link shows others get more or less:

Compare Side-by-Side

According to my math, and the trip computer, I'm getting combined 24.5 and 31 on the highway. I'm sure running the A/C will bring these down a bit.

 

Yes AC will always lower te numbers some which is ok with me but I would like to see if I can at least bump it back up or just improve the ride some over all

 

I got 32 mpg with 4 people, summer with a/c, cruising 100% interstate from Tennessee to Florida and back. And remember the tank actually has 16 gallons. For some reason the gauge is calibrated to show empty with 6 gallons left in it. Check your mileage the old fashion way by dividing the miles by gallons used between fill ups.

I'd change the top O2 sensor first. With 90k miles I'd bet it's never been changed. My .02

 

Ok and sinse the engine is a bit different then the truck, is the o2 sensor at the air box or is it going to be a PIB location on the exhaust pipes?

 

Both O2 sensors are located in the exhaust. I'm talking about the top sensor located just below the turbo but above the cat converter. This one affects fuel trims.

The 2nd O2 sensor is below the cat and measures the oxygen present after the cat does it's job. The fuel trims are not affected with this sensor.