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[aaronjb]

Crappy title, couldn't think of a better one.. anyway, since I've become convinced I'm getting quite a bit less mpg out of the knackered shed old girl recently, I thought it was about time I looked at some of the live data..

Haven't quite figured out how to record on the scan tool gizmo yet, so here's what I noted down:

All values taken with the dashboard temp sensor showing ~90C - it sits about 5C lower than this on the motorway at about the 85C mark.

At idle, initially:
ECT: 95C
STFT1: varying slowly between 2% and 4%
STFT2: 0%, steady
LTFT1: -2.3%
LTFT2: 0.8%
MAF: 3.5g/m
TPS: 0.8%

At 2000rpm held on the throttle:
STFT1: 0%
STFT2: Swinging between 0% and 4% slowly
MAF: 10.5g/m

Back at idle:
STFT1: -4% slowly rising to ~3%
STFT2: -4% and steady


Any clues there? They don't seem like enormous swings in the fuel trims, although the behaviour seems odd; the fact that the trims back right off after dropping to idle makes it seem like something got adjusted rich at 2000rpm..

MAF figures seem about right for a 3.2?

[Kevin Wood]

Not sure the MAF units are correct. Tech 2 reports in kg/h and typically it would be around 12 at hot idle in my experience.

The fuel trims don't show any significant problems, though. They will wander around a little as you have observed. Not sure if that's a temperature effect on the lambda sensors or just because the required trim varies with speed and load. Are both loops staying "closed"?

Can you see the pre-cat lambda sensor voltages? Are they cycling between rich and lean at a rate of 1Hz or so?

[aaronjb]

I'll have to double check the MAF units in a bit - maybe it was m3 or something esoteric; that'll make it a pain to compare to anything more useful (like a Tech2)!

I can see lambda voltages - unfortunately the refresh rate is a bit crap to tell that, though the O2 sensor graph is more useful. I'll check that next time I have the car up to temperature - and see if there's a closed/open loop indicator somewhere.

One day I ought to just make the time to run down to you one evening/weekend

[05omegav6]

Kevin is your man for that also he should have a good set of readings (from his car) and an 'interesting' set (from mine) Hopefully yours will be less 'interesting' than mine

[Kevin Wood]

Kevin is your man for that also he should have a good set of readings (from his car) and an 'interesting' set (from mine) Hopefully yours will be less 'interesting' than mine

Still, at least we didn't get as badly lost this time.

Does it give you MAF sensor voltage in addition to flow rate? That might be easier to compare.

[05omegav6]

 

[Darth Loo-knee]

Think my MAF read about 15-17 when revved up. About 12 on tick over.
When it was guzzling fuel iirc it was around 9...

[aaronjb]

Kev very kindly Tech2'd it tonight after a curry, in the pouring rain, and the dark, and the cold.. Owe you one for that, Kev.

Anyway - the numbers all looked alright though the Inj ms at idle was a little higher than expected - O2's flipping nicely, closed loop, 0% fuel trims (or very close to). Then we decided to test the multirams..

Not a sausage.

"Ah," says Kev, "Sometimes the little elbows between pipes come apart and .. Hmm, yours looks like it's popped off, here it is and, oh.. it's just turned to dust in my fingers."

So that might have something to do with it!

[aaronjb]

Multirams are now working.. on inspection in the daylight I found that the elbow to the front multiram solenoid was missing but, more than that, the output pipe from the vacuum tank had fallen off as the little connector there had perished.

Replaced those two sections of rubber pipe with some suitable silicone I had laying around in the garage et voila, now when I test the actuators with the *cough* there's a noticeable clunk and you can see them move as expected.

Now to see what the long term MPG is like!

[Kevin Wood]

Multirams are now working.. on inspection in the daylight I found that the elbow to the front multiram solenoid was missing but, more than that, the output pipe from the vacuum tank had fallen off as the little connector there had perished.

Replaced those two sections of rubber pipe with some suitable silicone I had laying around in the garage et voila, now when I test the actuators with the *cough* there's a noticeable clunk and you can see them move as expected.

Now to see what the long term MPG is like!

Should be a good bit more spritely now, too.

I think that elbow is now a pile of dust in front of a curry house.

[aaronjb]

It feels a little peppier .. hopefully the mpg will be decent, too, as the M3 now appears to be broken (the flappy paddle gearbox has forgotten how to use the clutch)!

[Kevin Wood]

It feels a little peppier .. hopefully the mpg will be decent, too, as the M3 now appears to be broken (the flappy paddle gearbox has forgotten how to use the clutch)!

Sounds expensive.

[aaronjb]

Could be! The diagnostic (well, SMG 'relearn' to teach it clutch wear values etc) fails half way through with a "4th Gear out of range" when it's trying to learn where the gear positions are.. forum help suggests the Gear Position Sensor is knackered (which may also have caused my intermittently dodgy 3-2 downshift) and the clutch issues are because the SMG has now (as a result of the diagnostic) forgotten the clutch wear values - it doesn't 'relearn' those until after gear positions..

Given the mileage, though, it looks like I need to do the clutch and sensor, and may as well do the gearbox detent springs (another known fault) while I have the box off.. before the 26th of this month when I'm meant to be hooning round Oulton park in it!


Anyway.. two runs up to Solihull & back this weekend and the Omega is now returning a more healthy 26mpg at ~75mph cruise with little traffic about. Not as good as when I first got the car, but a lot better than 18mpg!

[feeutfo]

Hmmm hooning.... Oulton Park, mmmmm those where the days.