Air Mass and 02 sensor

[mahadeshwar]

Hi Guys,

My car randomnly cut out twice while my wife was driving it. It also did it once previously.

The petrol gauge is a bit iffy if i fill it up on a it goes down to empty then goes to full after a while.

2 mechanics put it on the diagnostic machine and one said i need the air mass sensor replaced and the 02 sensor replaced.

The other said that he cant find a fault and i dont need to replace them.

What should i do and who should i listen too. My wife drives the car a lot with our baby and i am worried that it could cut out randomnly while she is on the motorway or something (although this has never happend to me).

Thanks

 

[television]

If the engine lamp is not on then ignore the O2 sensor, the MAF can fail in such a way that it can stall when you pull away

 

[jberks]

What model is it?
As Malcolm says, the MAS could cause a low power/stall but it all depends on what you mean by cut out. If it was driving normally and suddenly stopped then its more likely to be the crank position sensor. This won't show up on any diagnostics afaik. The MAS/O2 sensors may show a defect, many do and it may want replacing (I replaced them on my last merc but it still ran, albeit badly) so I'm not convinced its the cause of your problem.
What car is it and what are the exact symptoms?

 

[television]

What model is it?
As Malcolm says, the MAS could cause a low power/stall but it all depends on what you mean by cut out. If it was driving normally and suddenly stopped then its more likely to be the crank position sensor. This won't show up on any diagnostics afaik. The MAS/O2 sensors may show a defect, many do and it may want replacing (I replaced them on my last merc but it still ran, albeit badly) so I'm not convinced its the cause of your problem.
What car is it and what are the exact symptoms?

Just adding that the MAF on my V70 has failed in such a way that you go to pull away, say at a crossroad and it will or can just stall, but not all of the time.

With a CPS and a failure, there is always a ½ hour gap before the car will start again

 

[OmniCognateNeutronRangler]

The MAF on my w203 went and it made it stall at lights and junctions. The engine would go lumpy and then it would cut out. Had the MAF sensor replaced (not horrendously expensive - about £120 I think) and the car felt like a completely new car. I guess it had been going for a while. Incidentally, my MAF sensor didn't show up on the diagnostics thingy either when they pugged it in.

 

[brandwooddixon]

If the car won't fire immediately after stalling and needs a period to "cool down" then it's likely to be the crank shaft sensor.

 

[mahadeshwar]

C280 Mercedes

Thanks Guys,

Its is a C280 Mercedes 1998 Sport. What is the O2 sensor for? Why is it so expensive.

 

[television]

It measures the quality of the exhaust gasses, and passes information back to the input side on the engine,where the engine ECU will adjust the fuel-air ratio for a correct burn

 

[mahadeshwar]

thanks for your help all