Definitive cure for Misfire / 5.5k rpm limit

Well not necessaliry definitive but so far so good!

As some of you may know I’ve been plagued but a misfire (normally at about 7.3k rpm in 2nd and 6.5k in 3rd) which then limits the car to 5.5k rpm which is just no fun at all!

So spoke to Lotus who said to get it plugged to the OBD.

So off to Wilson’s who had heard of this before if you change the battery / loose charge as the ECU “forgets” certain maps that it needs, so �25 later and they’ve cleared the ECU and and put these map on it, so basically (as far as I can tell) reset it to factory (post recall).

Been having loads of fun on the way home! Everything touch wood seems top banana! It’s revving in each gear all the way (well only tested 3rd to that high for obvious resons ) and pulling a lot stronger too, some of the dead spots don’t seem as bad either especially from cold and it now idles correctly at 1200 rpm, rather than a sputtering 800 rpm

Obviously this wouldn’t apply if you’ve got an Emerald ECU / what ever but as long as it’s a lotus one then this seems to me to be the definitive cure


Good stuff

Don’t be surprised if you occasionally still get the 5.5rpm limit (cured by switching engine off for 10 secs).

As long as it’s not all the time then I’ll be happy

Brands Indy on Sunday will be the test! Bring it on! I’d almost forgot how f**king scary it is at full song grin

excellente Mark… hope that’s it for you.

So only work done so far is a reset of ECU right ?

Not just that, I’ve tried magnecor kv85 leads, new plugs, cleaning the wheel speed sensor up etc… But all to no avail.

It’s still happened a couple of times but has generally been it’s manic revving self

So far it’s the most sucessful cure!

Alas! It’s all rubbish! Didn’t make any difference where it mattered, the track

So onwards!

Did you get any running in ?

Running in? What’s that?

Where you able to get any good track time or was the day completed wasted?

LOL! Doh! Thought it was some technical term slaps head

Yeah, pretty much all the day was limited so just went out to practise my lines really and get a feel for the car holding momentum, so when I get this sorted I should be flying!

So it wasn’t a complete waste, just need to get it all OK for Bedford next month now!

OK guys, things are looking good here, it was the OSR wheel speed sensor that was duff.

Fitted a new one and so far so good, not a hint of misfireage

Something to note when fitting one is that it has to sit completely flush with the wheel hub bit, there’s arubber ring round the outside at the top which may need a bit of WD40 so it “pops” into the hole. Even if this a thou out then it’ll throw wheels speed errors and cause the misfire detection kit to kick in the 5.5k limit.

So all looks good and will keep you posted.

Thanks for all your help on this

Traveled from Peterborough down to Castle Coombe and mine started doing this.

Parked up overnight, no problem next morning. Then travelling back 60-100mph, started again.

Could dust from new pads and discs in this area cause the problem with the wheel sensor?

Is it a five minute job? as I want the car for Bruntingthorpe Saturday.

OK, easy to get to, jack up, driver wheel off and you’ll be able to see it behind the disc…

First off check the cables are OK and that the plug is clean. Even clean it up, dry it off and tape it all up

Next get a (IIRC) 10mm socket and get the sensor off. Make sure the end is clean and that it is sitting 100% flush with the hub, it needs to be about 100thou from the toothed cog inside. This needs to be absolutly precise!!!

Can’t see that dust would affect it tho’…

Let me know as I have a couple, one new and one that may work as it may just be a blown up sensor I’ll bring them to Brunty for ya… But will be in a MR2 SC

Thanks for the offer, just bought a new one to fit tonight along with some new HT leads.

Just thought that the only thing I’ve done to car since getting it was new discs and pads. The metal dust could be sticking to the sensor as it is going to be magnetic.

Looking forward to Saturday.


unlikly that dust could cause this… have you seen the size of the tooth pitch on the hub ??..

maybe you disturbed it tho’ when fitting brake parts ??

Actually found slivers of metal and dust surrounding the sensor. Looks the same as the dust now covering my wheels.
Cleaned the whole lot and put new sensor in, will test tonight and Saturday.

Be warned, hopefully you’re sorted but I replaced the sensor twice and both times it fixed it…

For about 2 weeks

My final solution was an Emerald (and cronic back pain from installing it LOL!)

Just to let you know i had same problem, after changing virtually all the sensors and going to the lotus factory twice. The last resort was a sreened cable which runs from ecu to lamba sensor. This cable is like a household ariel cable. When ecu was unbolted and moved away from bulkhead no misfire. The cable had a break in the centre of it, first time lotus had ever seen it. problem now solved.

Welcome andy1!

Top info for a first post. Come back soon.