Misfire.....but only under load

[pit_stop]

Help required please. Driving fine today, then suddenly it drops to a misfire, feeling like she is on 2 cyclinders. It clears, then does it again. Gradually I realise that at tick-over, or with no load on the engine she runs fine. Under load....back to the problems! Suggestions most welcome. Could this be the infamous cam angle sensor? If it is I'm disapointed as i only had it changed about a year ago, and was told that "the new replacement ones never give problems". Any help much appreciated.

Cheers.

[junks]

Help required please. Driving fine today, then suddenly it drops to a misfire, feeling like she is on 2 cyclinders. It clears, then does it again. Gradually I realise that at tick-over, or with no load on the engine she runs fine. Under load....back to the problems! Suggestions most welcome. Could this be the infamous cam angle sensor? If it is I'm disapointed as i only had it changed about a year ago, and was told that "the new replacement ones never give problems". Any help much appreciated.

Cheers.

Could be a number of things I guess but not sure if there's anything particular to Elans - spark plugs & leads etc can break down under load?

[pit_stop]

Thanks for that. I had considered this but decided against it on the basis that i thought I would have to be very very unlucky to get simultaneous faults on two plugs or leads.Have I missed something? Another bit of info is that there are no warning lights showing on the dash. Mention this in the hope that it might help preclude some possible options.

[router]

Maybe worth checking the coils, do you have a spark on all leads?

[pit_stop]

Yes. Sparks on all leads. Starts fine, ticks over fine, revs fine when stood. It is just when driving that the problem crops up.Paper clip tests shows no problems.Don't you just love electrical faults......particularly those you can only encounter whilst driving!!

[John_W]

pit_stop,
If you've already replaced the HES then (assuming a good job) it's not likely to be that. It's not surprising that your problem manifests itself under load, because by definition that's where things are most stressed. It's also not surprising that you might have lost two cylinders at once, since the fuel injectors are paired 1&3 and 2&4 and coils are paired 1&4 and 2&3. If a coil is on the way out, you could lose two cylinders. These aren't problems which would set up a fault code, however you might be able to see an injector problem on ElanScan - not a coil fault though. A HES fault probably would set an error flag.

There are a few threads which deal with this. I think the most relevant would be this one, or more poetically this one.

Basically, I reckon you need to investigate the coils first, then the fuel injectors. As it's only a problem under load, then either you wait until the faulty part is truly knackered and you can trouble-shoot it at idle, or you start swapping bits to see if it cures the problem.

John

[pit_stop]

Thanks for that.Sound and helpful details. I am thinking coils at the moment, but then..... last bit to the jigsaw perhaps is that when cold she seems to run fine....but once warm the trouble starts again. This may suggest carbutation. Just hoping that someone else will read this and go, ah ha! I had just the same thing and it was XXXXXXXXXXXX. At the moment my XXXX mean something completely different!
Cheers.

[DaveB]

Just hoping that someone else will read this and go, ah ha! I had just the same thing and it was XXXXXXXXXXXX.

'Ah ha'....or rather 'er...er...maybe'

I had the same problem...twice. First time it was coils...second time it was the leads...

Trouble is, if I get it again...it will be something else

[Freelander]

Me too! - Same problem - loss of power under load
Answer as stated above check coils then injectors.
I removed one plug lead at a time to check drop in revs.
If it is coils - best to change both as the other will probably fail sooner rather than later.

[Enright]

As resistance increases with heat (which is why superconductors have to be kept super-cool) I would suspect a coil-pack first.
Might as well do both at the same time as Freelander says, as the other pack won't be far behind - unless one half of your engine has done less mileage than the other!

[pit_stop]

Thanks for the advice. New coils fitted and problem sorted! Excellent. Just in case anyone is interested I got the coils from Car Parts Direct Ltd off the web. Delivered overnight at £30 each. Look identical to the originals. Lotus dealers quoted me over £100 per coil! I love a story with a happy ending !