misfire?!

[johnhay83]

i have a Jspec TT6, and when the second turbo jus starts to come in at about 4k rpm, it feels like it misfires, the boost gauge shows the pressure flicking between 0.6 and 0.8 bar and you can feel it to, but when i get to 5k rpm it stops and runs perfectly. i've only jus serviced it with new plugs, and haven't got any ideas short of getting a diagnostic done on it, any other ideas any one?

[Homer]

It could be incorrect plugs (or gap) but normally this is only evident at high boost levels..

 

What spec do you have: plug make and model, does the car have both cats in, boost controller?, uprated fuel pump?, any other mods?

[Nic]

Yep, agree with H most likely culprit would be wrong plugs or incorrect gap. Other thought is that the plastic connectors between wiring loom and coil packs could have been broken when plugs were changed and are now causing a dodgy connection.

[johnhay83]

i'm running stock boost, and only engine mods at the moment are HKS induction, and HSK front mount intercooler, the problem ony started yesterday but the plugs have been in a month. and jus to throw summit else in, it only happens when you have your foot down from the first turbo. if i bring the revs up slowly to 3.5k rpm then boot it, the problem doesn't happen. it's only when the first turbo is running under full boost then when it switches to the second one. i don't know what the plugs where i cant remember now!

[Stevie Boy]

Hey John is it?

 

Just wondering if you managed to sort out your misfire.

My cars managed to develop a misfire with very simailar symptoms.

Changed plugs in the process of trying to loan some coils to eliminate those as there not cheap to replace as a full set of 6.

[Robert]

he hasent been online for a month, not sure if your gonna get an answer

[Stevie Boy]

Oh well, the intermittant misfire is beginning to annoy me.

It developed after the last mapping session i had done on my E-manage but as it is intermittant it appears it can't be a problem with the mapping. However having been bout a month since it was done i've had a chance to drive the car a few times and when it does decide to occur its pretty much with the same symtoms as Johnhay, but won't neccesarily do it on demand.

 

Grrrrrr!

[Robert]

i guess just checking the plugs and gaps is the place to start but im sure you would have changed plugs after a mapping session

[Stevie Boy]

Yeah, can really do much bout the gaps as i'm using HKS iridiums removed the S40's (with only bout 6,000 miles on them) which were in there when its was mapped to see what condition they were in as i'd heard horror stories of the tips overheating, melting and causing a whole manner of damage in the bore, they looked completely fine and none of them looked different to the others to suggest a problem with a particular cylinder.

 

I replaced them with a higher heat range HKS S45's iridiums but exactly the same. I've removed the coils a few times to check them but all look ok visually but no way of testing them under load.

 

I may go back to the trader/mapper and see if they'll delete the E-manage mapping so its all back to standard, see if it goes away if not reload the map on and i'll have to look at buying or borrowing some coils.