SimonD

Apologies for adding to the huge number of MAF/Lambda threads but could anyone with some experience give an opinion on the following:

1. Sunday/Monday car starts to hesitate in the 2000 - 2700 rpm range. Above this all seems well. The problem is intermittent and only appears after a few miles when everything is hot.
2. Tuesday, no hesitation but the CEL lights up for a few minutes.
3. Today, take car to dealer who can see a O2 sensor fault. He clears the fault and says to try it over the next couple of days to see if it is ok.
4. Later today the idle becomes erratic and the car stalls a couple of times at the lights and is difficult to restart. CEL does not light up.

Are these symptoms of O2 sensor failure or could I have another problem?

Thanks in advance for any help.

zhastaph

Yup, both the off boost hesitation and the leaping idle are symptons of a failing O2 sensor.

Could also possibly be the MAF, but if the ECU has thrown up an O2 sensor CEL kinda confirms it.

Scott.T

iTrader: (2)

ECU can give 02 and MAF failure codes when either/or are failing.
It's been known on several cars on here that one seems to carry the other i.e a failing 02 and MAF may cause 02 or MAF failures to be logged.
Once you replace one the other error code then pops up a few days later.

I would replace the MAF ( £72) as it is cheaper then the 02 from Subaru (£120). Then pick up a £25 02 from a motorfactors if it still plays about.

If it ends up being the 02 and not the MAF you then have a spare MAF which is always good if it is an MY99/00

P.S Disconnect the 02 Sensor and drive for a couple of days like that. It shouldn't cause the CEL to come on, but may get rid of your problem. If it does replace it.
Running with it disconnected will cause the ECU to run from the Map rather then continuous adjustment in relation to 02 readings.

Jolly Green Monster

iTrader: (4)

Agree but I wouldn;t have thought the O2 sensor would cause the idle to stall.. float about a bit yes but I think it would just run rich and sit there idling no problem..

Sounds more like MAF sensor so I would as Scott says buy one of them first.

SimonD

Thanks for all the contributions.

Would the MAF give a poor idle?
What happens is that when I lift off the throttle as I come to a stndstill, the revs drop very low (>500 on the rev counter) and as long as it doesn't stall, the revs will settle back to a normal idle (with a little hunting).

This only started after the reset so I don't think that it is an issue with air leaks or the like.

Scott.T

iTrader: (2)

Classic symptons of a MAF failure, especially after a resset as the ECU cannot adjust to the failing MAF.

Get in changed ASAP, and don't rag the a*$e of the car until a new one is fitted.

TopBanana

Do universal lambda sensors work OK in Scoobs?

Jolly Green Monster

iTrader: (4)

I read the noticifation and had worded a reply in my head almost identical to that... get it sorted ASAP

SimonD

Thanks Scott/JGM.

Nice to get such a positive response. New MAF tomorrow morning then see what happens.

Jolly Green Monster

iTrader: (4)

Yes they just don't seem to last as long.. Halfords used to sell them L300 was the part number iirc..

Simon

Scott.T

iTrader: (2)

If using a univaersal O2 then get the 4-wire which will give you a proper earth rather then relying on the downpipe as the earth path.

Scott.T

iTrader: (2)

If it's a UK MY99/00 then you want a 22794AA010