Red October.

For some reason my work laptop IE doesnt give me the option to attach files, however my personal one does.

So, here is the link attached, to the full data download - gives MAF details & O2 sensor readings etc.

Does that shed any light?

As for the timing being out, I have no idea to be honest. Do I need to take the car to bits to check this or is there a more obvious diagnosis?

Cheers for you help, much appreciated.

Andy

 

edit^ done....I'll have a look see...

Any recent work on the induction? throttle, intake tube, air filter?

 

I'm not sure whats been done recently to be honest. Only had the car a few weeks amd bought it as a bit of a project (more a bloody puzzle!).

Anyhow, I've had the air filter out to inspect the MAF etc. Have looked at all the intake etc and checked all the plugs are connected, no cracks in the inlet tubes or vac hoses etc etc. As far as I can see at any rate.

The plastic breather tube connecting the drivers side cam cover to the air intake isn't in the best of health, (retaining clip broken), but I cannot see any signs of it drawing any air in. If it was dragging air in, would this not make it run lean? Or would the ECU make the car run rich to over compensate?

The running rich thing would suppoprt the fact that the plugs had a black (ish) sooty deposit on them when I inspected. Not the worst I have ever seen, but still black nontheless and I wouldn't have expected that.

I haven't managed to get any MAF cleaner yet but I will. I am actually on holiday from tomorrow eve, so if I go quiet for week thats why!

Cheers,

Andy

 

From the fuel trims we can tell that:
1) The ECU is seeing too little O2 in the exhaust, so thinks it's running rich, and is cutting back fuel to compensate (-ve LTFTs)
2) Something transient is going on (STFTs are non-zero both idling and revving - if the short-term trim stays put when running steady-state for more than 5 seconds or so the long-term starts to adjust to zero it out)
3) Whatever it is, it's affecting both banks the same

#1 could be caused by:
a) It's getting more fuel than it's measuring

• Fuel pressure too high
• Injectors worn
• Injector sticking open (unlikely because that probably wouldn't be equal on both banks)

b) It's getting less air than it's measuring

• MAF is reading wrong
• Air is leaking out. Unlikely because there's only positive pressure after the supercharger - anywhere else air would leak in not out, causing +ve trim. And anyway you're getting it at idle, when the supercharger's bypassed)

c) It's measuring the O2 wrong

• Dodgy O2 sensors - unlikely because they'd both need to be wrong for it to affect both banks, but possible if previous owner's ignored one bad sensor for long enough

#2 (transients) could be

• Misfires as a side effect of the main cause. If the mixture's so bad it's missing, the O2 sensors see too much O2 and add more fuel to compensate (+ve STFT). This can also explain seeing -ve STFT some of the time, because if it misses often enough, the LTFT drifts upwards , and the STFT actually shows -ve on the odd instant when it's NOT missing (that one did my head in on my car till I figured it out:-)).
• Intermittant causes to #1 above. If the problem's coming and going, the STFT could be banging up and down trying to compensate, and the LTFT is just reading the average of the short-term as it chases the short-term around trying to zero it. This one seems more likely than the misfires, at idle speed at least, since you say it idles OK

I'd say all the above points to most probably MAF. Could be O2 sensors, as Red October says, but both banks, and possibly intermittant (on both banks simultaneously) suggests not. Or maybe fuel pressure regulator sticking or fluttering (assuming there is one on these, I don't actually know).

O2 sensor state should be identifiable by the readouts you posted, but I haven't had occasion to worry about mine so I don't know what "good" readings look like: anyone else?

I doubt if it's timing, I can't think of a timing problem which would cause -ve trim. Timing problems would result in partial combustion (+ve trim), recirculated exhaust (no trim effect), or reduced air throughput (measured by MAF so wouldn't change trim). Worth checking though: if you don't know whether the tensioners have been done you need to get the cam covers off soon anyway to check that (and change them if not), at which point checking cam alignment's trivial.

 

Thanks Distraxi.

That's really useful.

From what I can see, you can get a replacement MAF sensor for circa £40, so I'll probably just change it tbh. By the time I've bought a can of cleaner & then decided that it's knackered, I may as well just change the sensor & have done with it. Rules it out if nothing else. I'll check the connections before I do, but I haven't seen anything obvious thus far.

If anyone has any wisdom they could share regarding the O2 sensors that would be good. One thing I did notice was that the data was only referencing O2 Sensor 2 for both banks. Shouldn't there be 2 lambda sensors per bank? If I'm totally honest I haven't been on a lambda hunt yet, so I haven't even worked out how much of a pain in the *** changing them would be!

This maybe an obvious question, but what condition would the MAF have to be in for it to throw a fault code?

Cheers,

Andy

 

I have some readings from my reader, maybe somebody can share a point of view:
Calculated Load Value 54,5%
Engine coolant temperature 87 C
Short term fuel trim Bank 1 0,0%
Long term fuel trim Bank 1 -1,6%
Short term fuel trim Bank 2 0,0%
Long term fuel trim Bank 2 -2,3%
Engine RPM 2447
Vehicle speed 107 km/h
Intake air temp 21 C
Airflow rate 43,32 g/s
Absolute throttle position 18%
Oxygen sensor output Bank 1 sensor 2 0,605 V
Short term fuel trim Bank 1 sensor 2 -0,8%
Oxygen sensor output Bank 2 sensor 2 0,670 V
Short term fuel trim Bank 2 sensor 2 -0,0%
Equivalence ratio lambda (Bank 1-sensor 1) 0,980
Oxygen sensor current (Bank 1 sensor 1) -1,465 mA
Equivalence ratio lambda (Bank 2-sensor 1) 1.005
Oxygen sensor Current (Bank 2 -sensor 1) 0,293 mA

 

Hi Guys,

Hope you are all well.

Back from holiday - it was very nice thanks!

Just a quick question having read Flay's post below:

Any idea why Flay is seeing an output for O2 sensor 1 on both banks 1&2 and I am not?? My output data only gave a reading for sensor 2 on both banks.

I am on the case sourcing a replacement MAF, but thought that this question may be worth investigating 1st?

Cheers,

Andy

 

Early cars have only one lambda.

 

Sensor 1 outputs are on the last page of the printout you posted

 

Hy Distraxi, can you have a look please on my figures? I suspect a vacuum leak somewhere as the engine is a little lazy.

 

Thanks Distraxi!

I hadn't seen those. Had assumed they would be located next to the bank 1 info.

Both Flay and myself seem to be getting some very different mA readings, although the equivalent ratios seem to be similar.

One thing I have looked at, is that Flay is seeing 43g/s airflow rate, where as mine converts to around 16g/s. Flay's figures are while under load (driving) and mine are not, but that is circa 3 times the rate I am seeing - assume this again points to a dodgy MAF? But the calculated load value on Flay's machine is 58%, whereas only 18% on mine, which again is circa 3 times - are these values directly related?

Flay - did you get any readings for Timing Advance at cyl#1 or intake manifold pressure?

Unless anyone has any other suggestions I'll chase up a MAF sensor this week. Fingers crossed!

Cheers,

Andy

 

@Andy,

I don't have a good handle on how the wideband (mA type) sensors work, but my understanding was that they read 0mA at 1.0 lambda ratio, and go -ve to show lambda one side of 1.0 and +ve the other. Which is what Flay's seeing but not you. Might be something there, but as I say, I'm out of my depth on that.

Anyone reading who actually knows?

Flay's airflow, throttle, and calc. load figures are all three times yours, which makes sense, he's under load and you're not. 18% throttle sounds plausible enough for a 100kmh cruise.

Calculated load is worked out a percentage of the maximum airflow you can expect at that rpm - it's got a complex relationship to throttle opening and rpm, as at low rpm the throttle doesn't present much of a flow restriction once it's partway open, where at max rpm even the last few degrees makes a difference. The exact derivation of cac. load is on the web if you care enough to look it up. I don't think it's particularly relevant here.

@ Flay, those figures look OK to me: trims are near zero and other numbers look plausible AFAIK. If you've got a vac leak you should be seeing +ve LTFT. Try it in Drive, stationary at full throttle with your foot on the brake and see if it looks the same. If it's down on power you need to see what it looks like when it's trying to deliver all its got....

 

Andy:
What your trims numbers are telling you is that the car is running rich at idle and then transitioning to lean as your speed increases. It would be interesting to get some numbers while under load at about 50 mph then while accelerating. Frankly, that is opposite what happens most often in my experience. A vacuum leak before the throttle plate will leak proportionally a lot of air at idle, causing the system to read lean, and the trims to compensate towards more fuel (positive).

The MAF is a very good suspect- If it is reading too much air at idle, this happens.

Another thing that can happen on SC cars is a leak after the throttle plate. I do not know if the after SC plenum is positive pressure at idle, but if it is, then I think a small leak at the two rubber biscuits between the SC and the intercooler could cause readings like yours. Mine were leaking a bunch, and they behaved differently.

It is unlikely you have fuel pressure problems, but that is easily determined with a test pressure guage connected where you can see it while driving. The fule pressure should stay about 2.7 bar above manifold pressure.

I agree with the comments made that your lambdas do not exactly line up with the other data, and I do not know which lambdas are used on your car. The lambda readings themselves move around a good bit, even for wide band sensors, and they are resolved into the fuel trim numbers for a stable parameter for control. It is always possible that someone put the wrong type sensors on your car, because the AJ26 engine and the AJ27 engine, at least in the X-308 and at least in the US use different sensors. I cannot comment on what was used on your side of the pond.

Good luck

 

Thanks Chaps.

Most useful.

I'll take another look at this later on today (still waiting on quotes back on the MAF).

@ sparkenzap: the possible leak at the two rubber biscuits - is there an easy test for this? I have noticed some movement in this area when you rev the engine, but expected that this is what they are there for?

Unfortunately I am not able to test the car at the moment while driving, as the car is without MOT. Unfortunately, I don't think it would pass an MOT as it is with this miss-fire, so there is a bit of a viscous circle here.

Cheers,

Andy

 

You can listen with a piece of 6mm tube stuck in your ear and listen fior whistles. Or you can feel around the edges of them to see if an edge is sucked in.

 

Thanks sparkenzap, I'll take a look

 

Andy:
Have you looked. Do you really have only two lambda sensors?

 

I haven't looked but it seems that I had missed the lambda data in the output. It was on a different page to the other sensor output.

I haven't checked anything yet as the battery has just given up so I'm hopefully getting a new one tomorrow. Then I'll do the checks on the supercharger before I splash out on a new maf.

Andy

 

Folks,

Would like to offer my sincere thanks to everyone who has supplied me with information and tips over the last few weeks. The new MAF arrived today and now she is purring as she should. Done a quick diagnostic and the fuel trims are all well below 5% and positive, so while i nearly choked at having to pony up nearly £140 (the non supercharged maf sensors are only £35!) its fixed the problem all is well in the world!

Wish me luck for the upcoming MOT!

Thanks very much guys, really do appreciate all the advice.

Cheers,

Andy