Ive been trying to get rid of this pesky light on my dash as my mileage is about 18mpg average.So far ive replaced both lambda sensors,had a local mechanic reset it but the light still came back on.Then i checked and found a vacuum hose with a big hole in it,I fixed this,reset the light and it still came back on again.Now im getting 14mpg average.Im just about to change my water temp sensor.Is there anything else to look out for and is my mechanic ok to reset the light or should i go to volvo?Can i disconnect the battery and get the same result?
Thanks Peter
Check engine light
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jblackburn
- MVS Moderator
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- Joined: 8 June 2008
- Year and Model: 1998 S70 T5
- Location: Alexandria, VA
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Don't just throw parts at it without reading the codes!
Get the codes read, your car should be mostly OBD-II compliant. This will give you an idea of what's wrong with it. Places here will do this for free.
Get the codes read, your car should be mostly OBD-II compliant. This will give you an idea of what's wrong with it. Places here will do this for free.
'98 S70 T5
2016 Chevy Cruze Premier
A learning experience is one of those things that says, "You know that thing you just did? Don't do that."
mercuic: Long live the tractor motor!
2016 Chevy Cruze Premier
A learning experience is one of those things that says, "You know that thing you just did? Don't do that."
mercuic: Long live the tractor motor!
Thank you for the advice but Im not throwing parts at it at all.The code reader said front lambda 1st,which i replaced,then rear lambda,which i replaced.I checked for vacuum leaks as the good people here suggested,i found one and repaired it.Then my mechanic said it could be the temp sender so i changed that as it looked old.There are no codes flagging up,do you think ive done the wrong thing replacing the parts the reader said were faulty?.
Regards Peter
Regards Peter
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jblackburn
- MVS Moderator
- Posts: 14043
- Joined: 8 June 2008
- Year and Model: 1998 S70 T5
- Location: Alexandria, VA
- Has thanked: 9 times
- Been thanked: 19 times
OK, sorry, just making sure. It just kinda sounded like you were guessing random things 
Usually if they throw codes, they are indeed bad. As you discovered, vacuum lines will also throw a code for O2 sensors, etc, so that's generally where I recommend starting. I wonder if a bad mass airflow sensor could be causing your issues? Does your car feel like it's hesitating or lacks power?
As for the temp sensor...does your temperature gauge act funny/does your car take a while to warm up or experience hard starting? Those are the usual indications of a bad temperature sensor. If you're going to replace that, go ahead and get a new thermostat too so you won't have to go back in and do that again.
Usually if they throw codes, they are indeed bad. As you discovered, vacuum lines will also throw a code for O2 sensors, etc, so that's generally where I recommend starting. I wonder if a bad mass airflow sensor could be causing your issues? Does your car feel like it's hesitating or lacks power?
As for the temp sensor...does your temperature gauge act funny/does your car take a while to warm up or experience hard starting? Those are the usual indications of a bad temperature sensor. If you're going to replace that, go ahead and get a new thermostat too so you won't have to go back in and do that again.
'98 S70 T5
2016 Chevy Cruze Premier
A learning experience is one of those things that says, "You know that thing you just did? Don't do that."
mercuic: Long live the tractor motor!
2016 Chevy Cruze Premier
A learning experience is one of those things that says, "You know that thing you just did? Don't do that."
mercuic: Long live the tractor motor!
No problems with heating up,it has plenty of power and theres no hesitation.I wonder if it is the mass airflow sensor,if it was playing up could it fool the car into thinking there was a problem with lambda sensors?
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