Misfire fix

[nelmo]

I've got a misfire that has been on and off for weeks now and is annoying the crap out of me. I've done pretty much everything I can think of, short of replacing expensive stuff (ie. injectors) so I would like to see if an expert can fix it.

Does anyone know, if I booked a RR, would they try and fix the misfire as part of the session? (I don't think the misfire is tuning-related. It was fine before my track day in May)

[Matth93]

Have you done a compression test?

[greenwoo]

nope, i'd say that the majority of R/Rds wouldn't check beyond asking you if its got oil/water in it.

How intermittent is it? Have you been able to pull leads to identify/isolate the affected cylinder and then work back from there? ( leads/coil pack etc ). I'm no mechanic ( no laughing at the back), but if its totally intermittent, then presumably its something that's breaking down when it gets hot? ( coil pack/lead/plug?)
Otherwise i'd have assumed that anything else would be a more permanent fault ?

[nelmo]

No, not done a compression test recently...will try that.

I've replaced all the HT leads, coil pack, spark plugs, crank sensor. Also re-wired the coil pack plug. Spent many hours mucking about with the Emerald ECU and datalogger, checked the lambda sensor (because that looked dodgy from the datalogger) but I think it is ok.

Engine idles fine and gentle acceleration is also pretty much ok - hard acceleration is bad.

@Mark, so if I turn up with a misfire, will they just send me home? Presumably, you can't tune a misfiring engine?

[Kegco]

Neil! you have pushed the HT leads on properly, Matt always comments that I haven’t pushed the leads on properly

[Tony B]

I think different RR places will have different rules, I’ve used Emerald and road & race and both of them have helped me resolve issues we’ve found during the session, however those issues weren’t complicated and they charged me for the extra time

I guess most places will sort out the issues for you, if you tell them upfront, but you’ll be on their hourly rate...

[nelmo]

Neil! you have pushed the HT leads on properly, Matt always comments that I haven’t pushed the leads on properly

Been there already ... But my misfire is not as bad as that...

@TonyB - thanks, that makes sense...

[jeffw]

Ring Atspeed and get them to book the car in to resolve the miss-fire.

[nelmo]

Ring Atspeed and get them to book the car in to resolve the miss-fire.

They look good - don't suppose you know anyone a bit closer? I haven't got a trailer and I'd rather not drive that far with a dicky engine...

[greenwoo]

is it def a misfire? or under heavy load does the engine just run badly? ( and does it do whatever it is doing whether it's cold or warmed up).

only 2 other things i can think of.....
is it getting enough fuel when you are planting the accelerator?
is the plug that goes to the coil pack 'perfect'....i've had 2 plugs 'go' over the years. The symptoms in my case was that the car would run fine until;
vibrations would cause the plug to move a faction making 1 of the internal connections bad which buggered up the firing
or after doing a temp roadside fix we put the connections back on wrong, up to midway in the rev range that was fine, above that it struggled and misfired.

If you havent checked the plug to the coilpack worth looking - and wiggling, in mine, from the outside it looked fine, but pulling/wiggling with the engine running proved the fault.

Good shout by Jeff because ATSpeed obvs work on cars/engines as well as having the rolling road, as Tony B says some rroads will do 'some' work, but they generally expect the car to rock up in fine fettle...and few will have bits on hand to fix issues.