P0303 misfire

[nydubber]

I've had this misfire for a the past week, I did tgv deletes and had a bad air leak from cylinder 1 injector, but no fuel sprayed out, went to get the car tuned, and now I have a cylinder 3 misfire, only under boost, around town driving and highway driving the car drives Great but once I give it alittle gas and get 4-6 psi of boost it misfires

I've changed the spark plugs and still have it I switch the coil packs and still misfire
Switch the injectors and still misfire on cylinder 3
Checked compression and all is good

What else can I look into to find this problem

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[UK-Wagon]

1) check all the related wiring a connectors at the injector, coil pack, and inspect the pins of these connectors and the main harness connection and pins.
2) Have a leak down test performed
3) check for another air leak

Who deleted the TGVs, if it was a DIY, which way did you do it?

If none of that resolves the problem you will need to take it to a shop and have it diagnosed.

[jaxscuby]

well we know mis-fires are either fuel or ignition related.

do as previously mentioned and check everything close to cylinder 3.

[nydubber]

I'll go everything Again

[nydubber]

Updates with a little more information

[nydubber]

Ok,i have narrowed it down to the cyl#3 injector. Its making a loud hissing noise at idle and Fuel is leaking out under boost,so badly to the fact that you can smell it. obviously the car starts to break up and misfire during all this.I have changed all the seals on the injectors and the gasket for the fuel rail. Im stumped. anyone have some input here? TIA

[Jkmaynard]

Put some gas on the injector seals before putting them in helps the seal up better

[04blu-sti]

Hi guys, i just had the similar issue.
Car would run fine on Idle but drop RPMS a little, but as soonest i try to hit BOOST Turbo STUTTERS & BOGS and throws P0303 code = Cylinder 3 Missfire.

Changed coil Pack from Cylinder 3 to 1 and boom Code PO301.

What i found was that I had big BPV leak, 1.5" seal broke in the Forge BPV Elbow. 2ND was the Coil-Pack Cylinder 3, called Dealer and they delivered it to the shop $83.00.

Car Runs smooth.
I was ready to stat messing with the Fuel pump already, i was thinking Walbro 255 went bad on me again.

Car Mods.


VF39 Turbo
Stock Injectors
KSTECH 73MM CAI
APS DR725 FMIC
PERRIN INLET
H.O.A. 3-Port Boost Control Solenoid
Walbro 255 Pump
TOMEI HEADERS & UPIPE
COBB DOWNPIPE
HKS CATBACK EXHAUST.