Zero misfires? Surely that's not right?

[sgould]

I was preparing for the service & MOT next week, and connected the Tech2 to further investigate the airbag issue.  So, while it was connected I ran through some other bits as the engine is vibrating on tickover and a bit above.

The Tech2 is reporting absolutely no misfires.  None at all.  Which is, to my mind, not right as misfires are normal.  I'm suspecting a DI or ECU fault.  Any thoughts?

[carrera]

Hmm,

What is a misfire and how is one detected.

IIRC, it is detected by the ionization signal from each combustion

I am not used to seeing any, unless the car has a problem. The counter is reset by pulling fuse 19 or disconnecting the battery

I have a couple of "failing" DI cartridges, they will chuck a P1312 & P1334 on startup, occasionally with a P0340. That's all to do with the wasted spark on startup. After the sync is obtained they run fine, and for years. I did read on trionic7 that there is a setting in the ECU that can make the ECU more tolerant, which stops the engine light appearing for a while, which either needs clearing, or will clear itself after so many cycles /starts

I wouldn't be concerned

PS, I see that you are saying there's a vibration on tickover. If it clears at higher revs, then I would suspect a poor spray pattern at low flow from one of the injectors. You could either look to remove & test, or put some Shell E5 petrol in with a bottle of Forte fuel system cleaner.

[sgould]

The only resaon I queried it is that I'm certain that there were misfire counts in the past. 

Not that misfires are a worry, I just look from time to time to see if one cylinder is wildly different from the others.  Misfires are normal and are registered on overrun when there is spark, but no fuel being injected.

I have no codes at all on the engine, just the airbag ones at the moment.

[carrera]

I have looked at misfires less frequently than you.... I suppose if it isn't broke don't try to fix it.

Misfire on the overrun does make sense, given the detection method. I also read that it resets at 65,000 counted. If I remember I'll have a look at one tomorrow

[sgould]

When the Carlsson started running very roughly a while back, looked at misfires and cylinders 1, 2, 3, 4 & 6 had misfires between 300 & 600.  Cylinder 5 was at 17,500.  So I pinpointed the cause of the rough running!!

On the 9-5 this week the Knock Count, at the top of the picture above, and all under 20; so again, nothing pointing at a particular cylinder or rough running.

[carrera]

Chucked the Tech II on the black car earlier today, and cleared the 1312/1334 stored codes that were no longer causing an EML

I had zero knock detection and just 1 misfire on cylinders 1 and 2

After a little idling number 4 had 4 and number 1 and 2 had increased to 2

Took her out for a short run, with a little 

I had some knock detection (stage 1 tune) and misfires on 4 had gone up to 7

There was no increase in misfires when on the overrun, so I assume the Swedes realised that doing misfire detection through ionisation when no fuel was being injected was a bit of a waste of time

Hope that helps

[sgould]

I will be driving down to Joe's tomorrow for the service and MOT, etc.  He's also got to look at the airbag.  I'm sure it's the clock spring now.  The resistance of the driver's side varies as you turn the wheel, but the other codes still exist suggesting a broken wire or rusty earth.

It was far too cold today to sit outside and play with the Tech2, so I'm not sure if my short driver through Watford and back has caused any misfires.  I may have time in the morning to look before I drive to the garage.

[sgould]

Just spoken to the garage.  My car is in bits...

They will have it for another day at least as they have parts on order.

Plan is:

New thermostat and coolant.
New crankshaft oil seal.  Sump currently off.
New exhaust flexy welded in today.  Probably failed because of...
... failed engine mounts.  One really bad, the others are "looking a bit soft".  All being changed when parts arrive.
Also awaiting a new clock spring for the airbag.

Then fingers crossed for the MOT.

[carrera]

IIRC the small exhaust section with the flexi is available for about £60 new, can't say I've ever come across weak engine mounts on the 9-5, but if i do I have plenty on the shelf

While the sump is off are you going to get the pickup cleaned & new o-rings fitted

Your car will be in quite a few bits while the crankshaft oil seal is being replaced. Are you goig to ask for the oil pump to be examined "while they are in there"

[sgould]

Don't forget that I have a 3 inch Hirsch exhaust.  But Joe reckoned that the engine movement was too much and contributed to the flexy failure.  It's stainless, but has a slight fatigue crack.   The sump was cleaned out 20,000 miles ago and was almost spotless then.  I hadn't thought about the oil pump, but the light goes out instantly

[carrera]

Ah yes, I had forgotten, and stainless is more suscepticle to cracking than carbon steel if I recall correctly

Pickup seems in good shape, you'll have her back soon enough

[sgould]

Picked the car up this afternoon, and after a 2 ½ hour drive on the M25 (it was only an hour going down...) I am home.  All work done except the clock spring that was sent without the adaption piece.  That will be done while I wait,  in a few days time, when I'm down that way.

But the steering wheel vibration is cured.  Four new engine mounts.  The gearbox mount was split and the top mount on the driver's side had completely collapsed. The rest was routine service, fluid changes, exhaust flexy & MOT.  The flexy was outsourced to a local classic car restorer who routinely welds stainless.

[carrera]

 

Always helpful to have pre-diagnosed what is wrong with the car before taking it in