Misfire problem classic
 

first of all my car is a 1996 jdm wrx saloon
jus fitted..

Walbro 255
Front Mount
EL headers
550cc injectors
NGK PFR 7B plugs
new coil packs
and had it mapped by duncan @ racedynamix, simtek

when under load it develops a misfire which bogs it down, around 6k mark,
any ideas? all the coil packs are new + plenty of fuel getting in

Have you brought it back to The person that mapped it?

Can you tell how many cylinders are misfiring? does it misfire at idle ?

Spark plugs gapped properly?

id say spark plugs 1st! even if they are new

Drop gap on NGK PFR 7Bs to 6.5mm even .6mm to eliminate them.
Where did the new coil packs come from and how much did you pay?
Was this misfiring during mapping and if so what was Duncan's advice?

As Harvey said, what did Duncan say?

Does it rev freely in neutral?
- also, under load when not up to full operating temperature?

Try checking for high resistance in wiring to plugs when engine is hot.

My slight misfire was sorted by removing the (newish) Racing 8's & putting 7B's in with gap at 0.6mm ... runs like a dream now.

TX.

I replaced 3 coilpacks for better condition used items (3 completely fell apart) when doing the initial mapping and cleaned the plugs up as best I could but the misfire still persists (although less than prior) - it ideally needs 4 new coilpacks and pfr7b gapped plugs to rule that out (whether permanent additions or borrowed). Potential for fuel pump weakening causing it but mixture was bang on the money so unlikely and fuel tables logical. It is a process of elimantion really. Getting a clean spark would be a good starting point IMO.

cheers for advice, checking the gap on the spark plugs tonight! lets hope it works

ok, gapped the plugs at 0.6 and changed the crank sensor still no joy :|, whats next? getting pretty fed up, considering giving it to a garage to sort out!

Hi,

I had something very similar on my MY99 recently, car missing and detting after 6k rpm on a rr session. Turned out to be my Crank Position Sensor - it was miss-reading over 6k rpm, showing as high as 11k rpm at one point! This of course triggered the ECU to kick the rev limiter in, which induces a rather severe miss-fire!

Changed the sensor and the car revved cleanly to the red line and all traces of det were gone.

I do still have an issue with the turbo not holding the full level of boost it should at higher rpm, but other than that it's going well.

Sensor was £170 FYI...that hurt!

Best of luck.

Cheers,

G.

ditch the crappy old style coil packs and fit newage ones

+1 - best and easiest thing to do:
http://www.jamessimpson.co.uk/classi...ack-conversion

any one able to do this conversion near colchester? pm me a price

I'll put a lot of money on it still being a coil pack problem. They should either be replaced with genuine new ones, or replaced with newage ones really.

Graham

i have a set of 4 in perfect working order if you want them £55 posted, cant be fairer than that,, pm me if your intrested,,, steve

newage ? if so i know someone who will have them if the op dont want then

For £55 you'll be inundated with buyers!

TX.

ill take them, pm me your details

make sure there newage mate, otherwise your throwing your money away !

will do!