URGENT HELP - Misfire on boost, Silverstone on Monday :(

[auzzam]

Hi guys

Was driving today at about 70mph and hear a loud pop followed by an awful juddering feeling

I notice the juddering (misfire) only happens on WOT around 4500+ rpm.
I immediately put in a new set of HT leads and a dizzy cap. The same problem persists

I changed my spark plugs two months ago and the car drove fine, but to eliminate the doubt I put the old ones back in (which I knew definitely worked)... Problem stil persisted

Could I have knocked any vaccum pipes off? I'm really stuck and I've got a £300 track day booked on monday


Please help

[Martin F]

You have changed the obvious so taking the noise into consideration i would next be looking for a boost leak, if nothing obvious i would closely inspect all pipes/clamps and dumpvalve for leaks especially underside of pipes that may be out of eye contact for cracks etc.

[2barGee]

Did you change......

Rotor arm?

King lead?

Is it boosting ok up to 4,500? Or is it boosting later in the rev range?

[alanmr2turbo]

had similar happen to me once, intercooler pipe blew off on way to Santa Pod

[Draven]

^^ as above had this before. split hose was the cause.

[auzzam]

Thanks all.

Small update... I disconnected the boost feed going to my ebc and turned it off. This obviously meant there was a slight boost leak but the car was pulling fine. More importantly the missfire had gone.

This meant working late into Sunday night, just before throwing the towel in we decided to take the car on the lowest boost pressure possible.


I'm probably going to look at reconnecting the boost feed to the ebc and unplug it electronically to see if the problem goes away. (Guess that would isolate the misfiring to the boost controller as even with the setting on 0 it was still playing up)


Any idea on which hoses to check for cracks? And has anyone ever heard of a possibly malfunctioning causing a misfire?


Will probably have look at it in the next week or so, for now just glad we managed to find a workaround and get rid of the misfire (all be it no longer running 1.2bar)

Was worth it to see the look on the old mans face as he was blasting around silverstone! - great father son bonding

[androo007]

Check every hose. Follow the circuit from air intake to turbo every pipe and pipe coming off. Turn check from throttle body back all way to ic both end's all way round to turbo.

You can spray soapy water around the joints and run engine to identify pinhole leaks.