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[Macie_UK]

Afternoon,

Having read many posts on the subject, I'm now at the 'sucking teeth' stage with the SO's barge, so hopefully an Omega guru can shed some light...

Preface:
Omega 2.2 petrol / manual box.  Engine management / MIL light has been on for *at least* the last three years - the garage that she had always used had advised her that it was nothing to worry about and wasn't worth fixing - and they have got it through the previous four MOTs at an average cost of £500.....

Anyhow, this time around at my local MOT place it failed MOT on a holed exhaust, so I put on a new back box and both centre pipes - failed the re-test on slightly high CO, and quite high lambda.  Upon getting it up on the tester's lift to check for any exhaust leaks (couldn't find any) we noticed that the post-cat O2 sensor had been disconnected.  Plugged it back in and the emissions readings were a bit worse - and clearing the P0170 code and light made no difference.

So, I've replaced the plugs, air filter and fuel filter, cleaned the throttle body and breather pipes, ran some Forte injector cleaner through it, and replaced a leaky vac hose - and the pesky MIL light still appears - sometimes after two miles, sometimes after thirty.  The thing seems to run very slightly better when the code is cleared, but the difference is hardly noticeable as it seems gutless for a 2.2 anyhow.  I also tried unplugging the MAF sensor and that made no difference to the way it drives or idles - well none that I could notice anyhow.

In my simple mind, it's down to the cat or the MAF sensor, but I've reproduced some live data below, in the hope that some kind soul will spot a glaringly obvious problem with some reading or other.  Please let me know your thoughts....


 

 

[Entwood]

Just my inane thoughts ...but lambda sensors are fairly delicate bits of kit, and to keep them working properly and clean, they have a built in heater. If your has been unplugged for a few years, as seems likely from your description, it is IMHO, very likely the lambda sensor is FUBAR. Best bet, if possible would be to swap with a "known good" one as a test. The "live data" you show is not very usefull .. it is the switching time that will tell you if the lambda is working. The fact is is staying Open loop implies the lambda control is not kicking in.....

but I'm no expert on these things ....

[TheBoy]

The trims are massively out. Is the reader reading them properly?

[Entwood]

The trims are massively out. Is the reader reading them properly?

If the lambda's not working wouldn't that throw the trims as well ??

[TheBoy]

The trims are massively out. Is the reader reading them properly?

If the lambda's not working wouldn't that throw the trims as well ??

If B1S1 was misreading, yes.  But MAF is more likely (or airleaks, vac leaks yada yada yada)

[Temetsy]

I'd say second lambda is fubar for sure if driven unpluged :/ That trim really seems to be faaaaaaar of the chart, optimal reading is ~14.7.

[Kevin Wood]

I'd say second lambda is fubar for sure if driven unpluged :/ That trim really seems to be faaaaaaar of the chart, optimal reading is ~14.7.

The second lambda sensor is only for cat monitoring, though. It won't affect emissions. It may well not survive having been driven around without the heater working, though.

I'm with the MAF/Air leak theory. Just trying to think if that MAF reading is plausible.

[Marks DTM Calib]

I make that about 7kg/h which is far to low

[Macie_UK]

Cheers for the replies, it is appreciated.
FWIW by 'switching time' do you mean the elapsed time between the readings fluctuating?  If so, I recall that it was certainly faster than a second, but can easily check again if it is important.

Am I correct in thinking that if the MAF reading is way too low, then it is a definite indicator that new one is necessary - regardless of it's effect on emissions and the MIL light?

Although it would be nice to kill two birds with one stone, getting the emissions low enough to garner an MOT pass is the first priority, which was why I initially was going to chuck a new cat on - although that obviously won't sort the fueling out if the trim is measured by the pre-cat O2 sensor.

[TheBoy]

Large air leaks and vac leaks can cause the MAF to read low, as stated previously. So you need to check this before condemming the MAF.