16v Track Car - Phantom Misfire

[ESD1711]

Morning all,

Wondering if anyone can offer up any words of wisdom in terms of helping get to the bottom of a phantom intermittent misfire i've inherited in my 16v track car.

Car is only used on track and as such hadnt moved over the winter - was parked up at the end of last years trackday season without any known issues.

Prepped and taken to track a couple of weeks ago for first outing of the year and noticed that it wasnt particularly happy at idling from startup - wanting a wee bit of throttle to prevent it cutting out and then if left idling for a while it sounded like it was starting to want to die.

None the less, it went out and did a few sessions without issue - till after lunch when from nowhere it started to misfire high up the rev range.

Came back in and pulled the plugs for a look at those - they were a couple of years old but didnt look too bad. Checked the gaps on them and found one to be a wee bit bigger than it should be, so re-gapped that and sent it back out. Seemed to go fine again for maybe 10-12 laps before the misfire returned.

Called it a day and stuck it back on the truck.

Decided to replace the plugs and check all the earths etc (only change made for this year to last was to change from standard battery to an odyssey so made sense to check earths were all ok on the back of that change).

So, new plugs in and earths checked - was back out on track last night.

For over 2 hours the car ran spot on exactly like I'd have expected it to and went quicker than ever before - problem solved I thought..... then out of the blue, the misfire returned.

So that leaves me with something which is apparently pretty intermittent. Firstly emerging after maybe 3 x 10 minute sessions, and then secondly being fine for over 2 hours of open pit and probably something in the region of 60 laps.

Where would folk be looking as next steps? Coil pack? Injectors? These seem like the obvious suggestions, but if either of those were having issues i'd probably expect the issue to be much more 'permanent' or obvious rather than being fine for so long.

All suggestions and ideas welcome - as with anything intermittent, its potentially going to be a bit of a headache to trace and fix.

[Manu]

a couple of years old but didnt look too bad

Replace.

[sri_130]

Any codes stored?
Coil pack first.

[MartinObviously]

I'm with everyone else on this, coil pack can cause this when it starts to break down - misfiring gets worse with heat.

Get a genuine coil pack from the dealer for £115. ALL the rest are shite - fact

The fact that it ran fine for about 60 laps or so after changing the plugs for new ones is tell tale as brand new plugs will have less resistance initially.

[ESD1711]

Cheers guys, I'll look in to a coil pack.

[karl_mh]

Not sure how your racing budget fairs but it could be worth making a cheap coil pack purchase to prove the fault then if this was the root cause of the misfire then move onto the at speed racing or spooks coil conversion kit for the reliability.

[MartinObviously]

Originally Posted by karl_mh

Not sure how your racing budget fairs but it could be worth making a cheap coil pack purchase to prove the fault then if this was the root cause of the misfire then move onto the at speed racing or spooks coil conversion kit for the reliability.

It doesn't work like that, it's not a case of longevity. The cheaper coil packs have incorrect resistance on the coil. it'll give you problems from the word go.

at a push a Bremi coil pack will be okay. AVOID siemens ones like the plague.

[sri_130]

Having been in saxo ownership for nearly 7 years, I've given up and ordered a genuine Citroen pack for near on £120.

Any others are just gash. I've chewed through tonnes of them over the years and even ran the wrong one on the dyno just recently.

Make sure you get the correct coloured plug for your model.