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Diagnose my duratec misfire
GreigM - 31/8/14 at 03:50 PM

Just looking for clues as I'm under a bit of a deadline to get this fixed.

2L duratec

On a track day today, car starts and runs fine. Do the session on track, all seems ok, but on the cool down lap back to the pits the car is misfiring quite badly. Get back to the paddock, it idles fine and when under heavy throttle (above 4000 rpm) seems fine, its only under partial throttle that I get this misfire.

I let the car cool down over lunch, start it up, all seems fine - revving up fine under partial or full throttle so go out for another session, car running well, again on the cool-down lap under partial throttle the misfire returns.

So symptoms seem to be:
HOT car
partial throttle misfire
idle fine, WOT fine

Plugs are new (<300 miles), so I'm leaning towards HT leads or coil pack - any other suggestions? Are there any sensors I should be thinking about replacing also (I'd rather spend money and get it fixed quick)?

owelly - 31/8/14 at 03:59 PM

Could it be fuel getting hot in the rail or fuel lines or has this set-up been OK in the past?

GreigM - 31/8/14 at 04:13 PM

quote:
Originally posted by owelly
Could it be fuel getting hot in the rail or fuel lines or has this set-up been OK in the past?

All been fine, no issues previously on other track days.

I'm kinda ruling out fuelling issues (maybe wrongly) as it runs fine at higher revs (meaning there is enough fuel getting through) - my simple mind thinks this must be electrical.

scudderfish - 31/8/14 at 05:09 PM

At WOT the fuel will be flowing through the rail. I don't know the duratec, but if the rail is dead-ended (i.e. no return from it) then fuel will be lingering and potentially vapourising in a hot rail

GreigM - 31/8/14 at 05:56 PM

quote:
Originally posted by scudderfish
At WOT the fuel will be flowing through the rail. I don't know the duratec, but if the rail is dead-ended (i.e. no return from it) then fuel will be lingering and potentially vapourising in a hot rail

Ok, understand and could be a possibility however I never had this problem before on hotter days with longer sessions. Previous owner never had it either and I'd bloody hope for the price of their cars Caterham would design the fuel rail better than this!

I'm going to nip out and examine the plugs shortly, just to make sure one of them hasn't had an issue..but as I said they are fairly new so wouldn't think so.

jacko - 31/8/14 at 06:04 PM

Wot make of plug's are you using ?

GreigM - 31/8/14 at 06:44 PM

quote:
Originally posted by jacko
Wot make of plug's are you using ?

Denso IT24 iridium

Think I may have found the issue, photo on the way

GreigM - 31/8/14 at 06:56 PM

Would this cause the issues I have? #2 HT lead has been pinched by the screw holding on the cover - i has taken off some rubber outer and I can see the green rubber inner (although I can't see any metal). I'll replace it anyway as a matter of course, but just need to know if i can stop looking for other things to replace.




[Edited on 31/8/14 by GreigM]

jacko - 31/8/14 at 07:19 PM

YES think you have found the problem

GreigM - 31/8/14 at 07:35 PM

Next question - are fancy Magnecor HT leads worth their money?

itsawindupuk - 31/8/14 at 09:40 PM

Id say so, I have them on my duratec, very thick insulation, look great and the quality of the plugs is spot on. They should last a very long time. Also you can have them made to any length you want.