Hi guys,

I did a few forum/google searches about a burning smell coming in through the air vents and didn't find much other than a possible turbo leak or burning engine oil.

The 1999 S70 T5 that I bought last week has been showing the check engine light for about 3 days now. As of yesterday, I noticed a burning smell inside the cabin after 5-10mins of driving coming in through the air vents (it got stronger when I turned up the climate control fan). Today, the check engine light is off and the smell of burning inside the cabin when driving is not so noticeable. I've been checking the exhaust occasionally for signs of white/blue smoke, but it looks all clear.

Might be relevant: At about the same time the check engine light came on, the AC/recirculation dash lights started doing their little '20-second blink' after ignition, which I understand means that the AC/CC system has stored codes. Could it be related to the burning smell coming from the vents?

Thanks
- D

 

Does it smell almost like burnt oil?
The vent system might need to be serviced.

 

Thanks tech. Taking it to get checked out tomorrow. It does not smell like burning oil.

The smell was worse than ever during stop and go traffic on the way home today, and I felt the car decelerating harder in neutral than ever before. I'm starting to suspect the parking brake (it felt really loose and only clicked about 4x when I finally got home). Any way to disengage it, even just a little, before I get it fixed?

 

If it was the e-brake after driving one or both side would be alot hotter than the front.
I also suspect you have a second problem if you have recirc on. If you have it on then I will bet your recirc door arm from the motor to the door is broke and not working. That would also make the A/C lights flash.

 

Good point. Another thing I forgot to mention is that the mileage dropped from ~22 (22 when I picked it up, 21-22 while I was getting used to the clutch for about a day and a half) all the way down to 17-18mpg since the smell started. I've been driving as conservatively as ever in the city.

Thanks for your input

 

Yes I would get it looked at. Also is the check engine light on?

 

The check engine light was on for the last two days, but it was no longer on this morning.

I didn't gun the engine very much before the smell started, so I'm not really able to tell whether there's been a decrease in power (it'll still boot when I drop the gas pedal )

 

Ok maybe they will pull the codes as well.

 

Had it checked out today and the mechanic says the oxygen sensor needs to be replaced. That would explain the poor mileage (and slight underpowered feel too?). Not so sure about the smell -- doesn't seem like the kind of smell that would come from the car running rich, but I don't know for sure.

The new sensor should be in by Friday, so I'll post back with results. Thanks for the input,
- D

 

Hopefully all goes well.

 

Thanks, I'm still waiting to head over to the mechanic to pick the sensor up though. Should be good to go tomorrow. The car's performance has noticeably dropped off by now... I've been taking it much easier the past couple of days as not to screw the cat up too bad.

 

Had the new O2 sensor put in today. While it didn't resolve the smell (thinking now that it's the heater core), it did massively improve the idle and low end performance. Thanks for the tips!

 

Glad things are getting better!

 

Hey I was just reading your post as I experienced very similar problem with my S60 T5 this morning. My engine vibrates and flutters as I begin to drive. But that same smell coming through the vents was unlike any smell I have encountered before. My milage dropped the same as yours too. I will be very interested in what the oxygen sensor does for you. Is that anything like a mass air flow sensor?

Don

 

I have had the smell with my 99 s70 t5, are running the heater? Also are you getting any smoke from the vents?

 

@Keith: A Google search would explain the heated air sensor (O2 sensor) better than I'm able to, but essentially this sensor is helps regulate the fuel air mixture coming into the cylinders. Replacing the front O2 sensor reduced the weird low-RPM engine behavior and improved mileage significantly, since the engine was no longer running rich (when the fuel-air mixture that contains too much fuel). The smell while driving did go away, yes.

@xxblindxx: No smoke from the vents. However, yes, a burnt smell (different from the smell when the engine was running rich) does come on when I start the heater. After running the heater for a few minutes the burnt smell goes away. The mechanic suggested that the heater core is dying.

As you can tell I've had some confounding issues with weird burnt smells Car runs great now, though.

Good luck guys

 

I'm sure it's the heater core, I don't know if this is an issue with these but I've had it happen to my 00glt and 99t5.. So that should fix it.

 

I have a '98 S70 GLT and also noticed a smell from the vents with or without the ac or heater on. I noticed the smell being burnt or heated anti-freeze.

I tried to "kill" the smell by changing the fresh air to recirc and it did the job. BUT I noticed that the recirc woud switch back automatically to fresh air by itself after a few minutes, no matter what I did (change to floor, upper, window, mix, etc....)

I am curious as to how much a "service" would cost $??

I am a newbie in the Volvo world with the S70 being my first. I bought it used and use it for daily local driving (with some fun when no traffic is around)

I also noticed that the fresh air/ recirc buttons flash for a while when I start up the car. Wondering if anyone know what that is about and if thats ok?
Thanks in advance to all you guys!