Missfire/backfire under track conditions

[Tuga2112]

ECM fuse is the top right fuse (number 5) in the passenger footwhell fuse compartment.

if your on facebook. i can post a screenshot of the manual there.

putting images in here is a bit of a faff.

[chrism]

[MPx]

Thanks Joao - not on any socials - various car fora are as close as I get. But Chris has done the deed so thanks very much Chris. I don't think I've got any excuse now - fuse 5 will be pulled and replaced before my next run.

[Tuga2112]

chris has the patience that i lack.

in my defence, you guys get my replies often while im at work while waiting for the kettle.

[RonR]

I assume the fuel map is less lean on 4.5?

Yes Mike the V5 runs the AFR leaner to give a bit more power than V4.5. The ECU has a 3D table, using RPM and Manifold Pressure to find AFR. It can then be modified or overridden, e.g. if cruising (Highway mode).
In the table, Mountain V5 varies between 1.6% and 10.8% leaner than Standard.

It would be interesting to know the RPM and MAP figures for each of your knocks, maybe a pattern would emerge.....

[MPx]

Had a run down to Exter today to the "Sanctioned" car event there. Elan behaved perfectly both ways as normal.

Before seeting off, I did pull/replace the 10amp fuse from pos 5 which I hope did the ECU reset. But I don't know where it was flagged as an error. I see the promID on both recent logs (before and after fuse pull) was 699.

Over the circa 50 min trip I see I got just 3 knocks - but again no retards recorded.

I did look at the knocks vs Wastegate duty cycle as per Ron's previous spot. Again it shows a close-ish correlation - but also more cycles without knocks than with.


Also had a look at Knocks vs MAP and RPM as Ron suggested but both graphs were a bot too busy to tell very much at all with just 3 knocks vs continuous data. Looking back at the previous trip with more knocks - it was also a bit busy, but to my eye the knocks were more obviously recorded when RPM increased very rapidly. Trouble is there were plenty of similar rises with no knocks so way off conclusive of anything.

Anyway, as I said - the car was perfect and very fast for the public road today so really I haven't got a problem have I ?? Well we'll see next May at Combe!

[MPx]

Well having just had a wonderful day at Combe on Saturday I'm happy to report that regardless of anything the data might say (and I don't know as I had no recording) the car is back to its very best. Its not been this good since the 30th anniversary meet when I was lucky enough to cheuffeur around a few of the great and the good - really showed what the M100 is capable of even in numpty hands. This time I had 4 sessions - and unusually 3 "sighting laps" to start the day. Seemed odd to be told I must do the sighting laps when it was my 34th outing at Combe... but so be it. I was able to maintain max chat throughout all 4 sessions with no misfire, no backfire, no loss of power, and it feeling very racy. Absolutely loved it!

Many many thanks for all of the support and help offered by so many throughout this process and especially Ron through Elanscan and SWLCP trialling/replacing various bits and pieces over several years. Nevertheless I'm going to take the lions share of the credit for the eventual "fix" by finally doing the base timing check/adjust myself (as several people suggested I should!) despite it having been checked and rechecked by others several times. That seemed to be a step change and everything has felt better since.