Your thoughts on a temporary misfire...

[MPx]

Grateful for some help please.

As several of you know I had a fantastic day at Combe at the end of May where the car didn't miss a beat despite 6 very spirited sessions on track - plus the journey to/from.
But as is all too typical these days it has not been used significantly since until the trip up to London for the Evija launch. It had been started and warmed up a couple of times and to maneuver for cleaning etc but no miles as such. So I set off on Tuesday and all was well for about 10 miles. Then on the A303 I got a bad misfire accelerating off a roundabout. I eased up but the misfire continued sporadically for about another 10 miles. Soon after I pick up a mate and while at his house had a good look around under the bonnet for anything loose or different - couldn't see anything wrong. We set off from his and all was well for about another 10 miles but then the misfire started again and despite my easing off continued and eventually the engine light came on. Soon after I stopped at what I thought was a classic car garage which turned out to be just a body shop, so we were only there a minute or two. When I restarted the engine light was off and we continued on our way. I was (very) nervous of not making the launch event and since we had allowed plenty of time every time it missed a beat I slowed and we got up to London having been cruising at around 60 on motorways and dual carriageways. The misfire did not affect us at all for the last hour or so of the journey. We then had the yellow Lotus parade around central London in glorious hot sun and typical mostly stopped traffic. No problems with the car at all. Eventually it was time to come home. We were early enough to catch the tail of the London rush hour traffic - no problems. Once outside the M25 the roads cleared a bit and we started to, ahem, make progress. I was going as fast as I ever do on the fast roads on the way back to Gary's and it never missed a beat in 100 odd miles. Once I dropped him off I gave it the full beans on some roads I know well to get home and again absolutely no issues at all. So:

I was going to connect up for an Elanscan, but since there's no issue now I doubt it would show anything useful. On the other hand I'm a bit bothered that just putting it back in the barn under its cover may mean I get a sick car when I next want to use it since I didn't "fix" anything. I'd be interested/grateful for any thoughts on what might have been awry and what may be the best way to check that it really is alright again now.

[dapinky]

Without any further information, I can only say what I would be looking at (and hopefully, in the appropriate order)....

First, I would suspect the ignition leads - check each end is fully seated, and then remove each from the plug and check that there isn't a breakdown where the cable goes into the plug cap (some of the aftermarket ones have been known to detach themselves, sometimes giving a complete breakdown, sometimes rectifying themselves, depending on how the vibrations affect it).

Then I'd look at the plugs themselves for damage to electrodes and/or insulation (ceramic bit).

Next it is down to the injectors/coil packs - but only if the missfire is ocurring in a 'pair' situation - if it is just one cylinder, it's unlikely to be those - but you never know.

Unlikely to be a mechanical fault with valves etc, or it wouldn't fix itself....

.... after that, I'd ask on LEC for any further ideas

[Giniw]

I was going to connect up for an Elanscan, but since there's no issue now I doubt it would show anything useful.

The ECU stores the fault code for a while so it will definitely report it (I think it clears the fault code after like 50 trouble free runs)

[Rambo]

I'd be doing the same as Dave suggests. It's the logical order but I must admit that my 1st thought when I read your story was coil packs

No harm in doing the paperclip test. You might just get an error code thrown up

[John_W]

I hate intermittent faults! I spent a year tracking down one that sounds like yours. Elanscan did tell me the fault code, but it pointed me in completely the wrong direction. It pointed to CAS, so I replaced that: all well for a while then misfire returned. I changed plugs, checked and re-made HES connections, and a few other things.

It turned out to be plug leads. Not in the expected place Pinky mentions, but just as the leads enter the cam cover - one of them had gone floppy so there was obviously an intermittent connection. The good news is they are cheap to replace (once you’ve replaced all the expensive bits!).

Good luck, (and tell us the fault code)
John

[Rambo]

They can be cheap and cheerful but watch what you buy on EBay because there is cheap rubbish on there.

What did you use John ? From memory I replaced the original ignition leads on Rambo with Magnecor KV85's

[John_W]

I changed the original (red) plug leads in 2004 to the Kingsbourne set Nitroman organised a group buy for at the time, then in 2017 replaced them with a set of Cambiare ones because no 2 lead had gone bad. It looks like Elan plug leads last 13 years exactly!

I bought the Cambiare leads as an Elan-specific set off eBay seller "qualityparts09" for £26.70 and they appeared very good quality. They have been great ever since (6,000 miles covered with no further misfire - not counting a failed injector )

[MPx]

Thanks chaps. I replaced the coil packs and leads (it turns out back in 2011 although I thought more recently) covered in [list=]this thread[/list]. The coil packs from Ignition Car Parts and the leads from Kingsbourne. So only 8 years old and probably done <15k miles.

But its a good place to start ...so I will...as well as looking for a recorded fault code. Won't be straight away though as I'm at the Sherbourne Castle Show tomorrow with the Esprit and then away for a couple of days. I'll be back...

[Bern]

I saw your Esprit at Sherbourne, the number plate gave it away!

A lot of cars, plenty of Esprits and Elises, but the only Elan I saw was a +2. Mine was in the car park, I didn't want to wait until 4pm before leaving.

[MPx]

Yeah a good show after the sun came out Bern but nevertheless I was keen to leave before 4 so may adopt your strategy next time. Shame there were no M100s but 4 G-Esprits is a significant turn out for a regional show - not seen that for a while. The one I parked next to looked to be in lovely condition.