I've been looking all over this site to see if I can get a straight anwser to solve my misfiring problem. The problem im having is as soon as the car hit boost it starts to misfire. I'v got colder spark plug gapped at .030 checked my coils. and still misfires no matter how much lbs i put. im currently at 5lbs, any suggestions would be appreciated

 

first off....setup?

Auto or 6spd?

Any grounding modifications?

Try gapping plugs down (like .025 and .020) and see if that makes a diff.

Tom

 

It could be many things... When was it tuned? You have a wideband? Whats A/F when boosting? Need moar info.

 

Any specific cylinder?

 

I am experiencing the same things right now and here is what I have came across as possibilities:

1) Bad Crank Position Sensor
2) Bad Cam Shaft Sensor(s)
3) Shorted Ignition Circuit
4) Shorted Fuel Pump Circuit
5) Shorted Injector Circuit
6) Bad Camshaft Position Landing
7) Dirty MAF Sensor
8) Dirty Throttle Body
9) Bad Throttle Body
10) Bad Injector(s)
11) Bad 02 Sensor
12) Bad Grounding
13) Bad Spark Plugs
14) Bad Stock ECU
15) Dented Flywheel Position Ring
16) Improperly Timed Cams (assuming a recently assembled motor)

Those are just a couple thing which unfortunately don't really narrow it down at all. Other obvious things are the tuning and parameters of whatever you are using as engine management.

I am currently sending my injectors in for testing and cleaning. If they come back okay I will be checking the cam timing and from there replacing the crank angle sensors unless I get fed up with it and just go standalone.

 

I bet it's (1) or (2) on your list.

Would be nice to know what codes are being thrown.

 

Sensors maybe if he was misfiring all the time, but hes misfiring only under boost. What codes do you have? Need moar INFO!!!

 

I've been random multiple misfire, and o2 heater too high.
I am auto, I did add to extra grounding point and it help a bit. Its not a particular cylinder, It just a stock motor, custom fuel return system, fuel pressure set at 60psi with stock injector. T3/T4 turbonetics 60 trim.

 

interesting... stock injectors @60psi... so who tuned your car? What is your A/F ratio when you misfire? Was your car tuned running well until now? Or are you still trying to get it running right?

 

It sounds like plugs.....Seen it so many times on Dyno. This is called spark blow out.
I would start your gap at 28 and work your way down.

How much Boost? any CEL's?

 

I went to the dyno and the car was misfiring so I could get a good session, the fuel pressure was dropping instead of increasing so I which fuel pumps and got a walbro 255hp. Beening that I live in south florida when its about to rain and I get a cool breeze to the car feels good,but then it starts to mis again.

 

Is your fuel pressure increasing now, and what are your AFR entering boost?

Gapping .030 should be more than small enough for your amount of boost/power - there is no need to go smaller, something else is wrong if so.

 

Misfire is usually caused by spark blowout which I doubt you are having. Next item on my personal list is your a/f ratio. Too lean can cause misfires, too rich can also cause misfires. If the misfires are because you are too lean then your engine could be toast. What are you A/F ratios like across the rpm range?

 

I have'nt been back to dyno yet, but I am working on gettin a wideband and doing some datalogging.

 

Which can also be caused by a bad or clogged injectors. Seems like the OP has opened the fuel system up since he has a custom fuel return system.

 

I know this is old but I finally figured out that it was my #2 coil pack going bad. the car runs like a dream now...

 

check and see if u have any oil in ur plugs, i was also misfiring under boost and when i went to check the plugs they were full of oil that had leaked so i put RTV silicone