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[jtypecav]

Unfortunately we haven't got the the bottom of that yet.

That's the bit that worries me! 

[Kevin Wood]

It would be interesting to see ignition advance and knock sensor output on that table plot if you have them.

..And you're right, engine load does look low, assuming it's reporting it in %. Not familiar with that software.

Intake valve operation looks as expected (it's only based on engine speed and TPS so should be right).

Oh, and did any codes pop up when the EML started flashing?

[jtypecav]

Yup, our friend 300 and 304 and 306! That was all.

What stumps me is that it's speed (or gear / load) related as it'll rev to 5 easily with no light in 1st. Hence all the colour coding.

I do have the ignition advance and knock sensor output for the same period. Will edit and get it up.

[Kevin Wood]

An engine accelerating in a low gear is effectively more lightly loaded than in a higher gear, though, since the rate of change of speed is higher. If knock or a misfire are to occur they are more likely in a higher gear than in a lower gear because the conditions exist for longer as the engine accelerates.

Was a misfire evident when it starting blinking the EML?

[jtypecav]

The blinking seems to indicate "oi you have issues" and very quickly - almost instantaneous - we are cut. Bizarrely the drive it up to 4.5k againa dn you loose 5th cyl too thing continues too!

[TheBoy]

Hmmm, how convinced are we that the replacement MAF is 100% good?

And, can you confirm, this has a bog standard air filter, not a silly cone, or an oiled filter?

[jtypecav]

Yup 100% certain AFM is known good. Bought it about a year ago GM new and was driving up till a month or two ago.

Filter looks clean and is a FRAM or similar generic. I checked the piping this morning when doing the AFM in the rain.

Oiled filters kill MAF I know this as the Ascona doesn't have room for an airbox so runs a pipercross and uses a MAF every 2-3 years give or take as it's more and much closer to the filter too. Would never do that to the MIG! 

[TheBoy]

OK, so changing MAF has made a difference

So, either we're on the right lines, or maybe Kevin Wood's 2.6 experience is skewing the results 

Wonder if a reset of the BLMs would be worthwhile, now another MAF is on 

[jtypecav]

It occured to me that it could be cold start that skewed it working in 1st gear. So as it's so close I think your right and we assume we have modified slightly but the symptoms and cause remain the same unhindered.

However, slightly worryingly, there is no data in the table for Knock Sensor 1 & 2! Is this the cam sensor that connects near the front cam cover on a FWD Vectra etc?

Here's the ignition data I had from that run.


Ignition Dwell Angle - Always 1.7ms
   Injector Time   from 7-25ms on average
                Spark Angle -12 to 25 CA throughout the run.

[jtypecav]

No knock sensor data from past runs whatsoever. What sort of values are typical here?

[Kevin Wood]

No knock sensor data from past runs whatsoever. What sort of values are typical here?

Active or inactive I believe. Shouldn't be Active at any point, if all is well.

Given that there has been a difference, I wonder if the fuel trim up at heavier loads is still leaning it off too much, resulting in a misfire or knock which the ECU, rightly, responds very aggressively to, since such things kill engines. Can you read and clear the engine codes? That usually clears the fuel trims on a DBW car. If the code reader won't do it with no codes, fire it up with a multiram solenoid disconnected to create a code.

Then again, I've seen MAFs change symptoms on a 2.6 before with out a total cure. As I said, they seem very fussy.

[jtypecav]

The AFM discon this AM gave me codes, as did the misfire 0300 which got stored, which I've cleared to be able to drive it back from testing etc.

[jtypecav]

Drove this to work today. I simply can not get my head around how well it drives, how well it pulls to the limiter if you avoid "full load / Invalid".

 It runs so smoothly for this to be anything major. It's killing me not knowing. Damn my OCD. It just doesn't add up.

[Kevin Wood]

I'm starting to wonder if it's a drive-by-wire failure.. but if that were causing it to go into limp it would certainly raise some codes.

[jtypecav]

And swapping out the TB from a 3.2 and a pedal sender didn't change the symptoms either. 

Unless there is something about a 3.2 not working on a 2.6 and vice versa - but my bits seemed fine on his 3.2 too!