I've been looking at a Subaru Forester recently for a mate that has a strange fault.

First thing in the morning once its run for a minute it will cut out then crank over as if it has no compression for another min ?

I put the scanner on it and noticed that the lambda was not switching much more than .7-.8 volts.

Surely in closed loop that would switch more than that ?

If you leave it for a while it will drop down to .2 then slowly rise back upto .8 again.

This is when the engine is hot and it should definately be in closed loop control imo.

I'm thinking the lambda must be faulty although I'm still suprised its fluctuating (sp) a bit.

Any advice or info on the particular car ?

It is a turbo forester btw

 

when cold no car runs closed loop to the exteent where the AFR is 14.7:1

Cold start needs more like 10:1


COuld that be what your seeing but it doesn t explain the fault....

 

Thats originally what I though Alex but its the same when I am driving around in it.

I was suspicious that the closed loop function had packed up on the ecu tbh.

 

exhaust gas needs to be at 400-600 deg c before lambda will work

 

Mitsy - unless its a heated sensor - they work from cold.




That function can't just pack up - it just doent.

It'll be a sensor or the wiring.

Alex

 

Sensor it is then

Thanks

 

It is the switching SPEED you need to watch NOT the voltage.
tabetha

 

The switching speed is very slow which is why I thought the lambda itself or ecu was at fault.

New Lambda from Subaru is Ł175 + vat

Glad I'm not paying for that

 

I thourght they went closed loop after 3000rpm

 

If you need a new lambda shop around as you can get one a lot cheaper than that, have a look on scoobynet may get some advice off there.

 

That would be open loop mate

I'm not exactly sure where is changes over but off boost (or low boost) whilst cruising is usually closed loop control