I've had a noticeable misfire since I bought the car. I finally got an aeroforce interceptor to monitor it and it is ONLY at idle and to a lesser extent at part throttle. WOT is perfect. It's showing a majority of the misfires on cylinder 4(like ALOT, 20 per cycle sometimes). I just replaced all plugs and coils. Mods are as follows:
2.9" pulley
#60 injectors ?
stock h/e for now
zzp CAI
I believe it has a canned tune from zzp

Is it possible the injector is struggling at idle but fine at WOT? Or is there something else I should be looking at. Plugs are gapped at .032.

 

Do you have air/fuel ratio gauge? How did your plugs look when you pulled them and did #4 look worse than the others? At this point I wouldn't assume your problem is mechanical as it sounds like the tune status is an unknown. If you don't have AFR gauge you need to get one. Canned tunes usually have pretty bad fueling and can cause misfires. Also let us know if you are throwing any other codes.

 

Don't have an afr gauge, plugs were so overdue and wrong (ac Delco stickers) but no big difference between the four of them. It can't be the injector? I was planning on swapping them when I get the chance.

 

It could be the injector but most likely that isn't the issue. I would highly recommend against swapping any physical components without narrowing down the issue with more precise diagnosis. With each new component you introduce a new variable.

You absolutely need an AFR gauge/wideband sensor. The only thing the narrow band can read is if the fuel mixture is leaner or richer than stoichiometric.

Where your injector tips black?

 

Buy a multi-meter and pin out the injector harness to the ECU and check the constant 12v source. Wiggle the wires around while testing. Never stick anything into a harness connector (like a pin or paper clip), if you need to do it then do it from the back side aka back probe.

My 2006 Ecotec throttle body wiring broke a wire internally, inside the wire jacket!! It was an intermittent issue for a long time until it finally fractured, while I was cruising woodward also. I ended up buying a whole soldering kit while limping it home and fixed it i the parking lot after finding the root cause, went back out to the cruise was a happy ending.

 

Finally got around working on this. The spacer for the injector that seats into the engine was pretty dirty and slightly damaged. Since I didn't have a replacement I just cleaned them all up, swapped the injectors around to try to isolate the problem and now it's much better at idle . Good enough. I didn't do much but maybe this will help someone in the future.

 

If the injector isolator was damaged you could of had a vacuum leak there. Other possibility is you have a connector with a bad connection to injector or connector not properly slid on the injector all the way.