Engine Misfire Codes
 

Hey guys, 4 weeks ago I finally got my tune, and I love it, it really brings the car to life. The week after the tune I changed oil, oil filter, and plugs as my car just hit 100K miles. The week after the oil change my check engine light came on, but turned off before I got the chance to have it checked. Well, a week later and its on again so I just got the code read and its throwing misfire codes on all 4 cylinders as well as a P0300 code. Any suggestions on where I can start to fix this issue?

I had a misfire on cylinder 4 when I was tuning and replaced the coil pack for it and it was fixed. Maybe you need all 4 coil packs or you need to verify the gap on your plugs?

Do you feel misfired happening? Like do you get a flashing CEL under heavy acceleration or do you feel it miss at idle or any other time? A possibility is your spark plugs aren't gaped correctly giving you spark blow out under high boost.

I dont feel any misfires, even under heavy acceleration. Ever since the tune cold starts lope hard as hell like it has a cam. Other than that I havent noticed any performance changes. No flashing CEL, it just stays on.

Sounds like your cold starts may be were you are getting misfires. If you rev it up a bit when it is doing this does it sort of sound like a Subaru boxer engine?

Lets slow the roll on replacing coil packs.

What plugs did you use and what gap?

Rough cold start is the first sign of fouled plugs, they usually start acting up in high load next.

^Very true from experience. I don't have LNF with DI but same symptoms with fouling plugs

No, it has normal tone when I rev it cold. Holding any amount of throttle stops the lope, and it stops after a minute or so and idles fine.

AcDelco irridiums, not 100% sure about the gap. The lope started immediately after the tune and before the misfires started showing up.

Sounds like the open loop tune needs correcting which means closed loop is correcting an improper base tune. Your long term fuel trim numbers will tell the truth and probably show it cutting back fuel which is fouling plugs.

In short... It was tuned for power enrichment and not overall. Sad but common.

Take it back to your tuner, idle on the LNF is a bitch to settle down but it's certainly do-able.

FYI: Your tuner. (if he knows what he is doing) can force it to open loop to tune that section. Open loop doesn't use the O2 feedback so it doesn't need to be cold to do that.

This isn't an LNF thing... If he cannot tune an engine in Open Loop and only tuning it for Fuel Enrichment mode, he shouldn't be taking anyone's money and saying he is tuning. He is relying on the PCM to take care of the running quality in closed loop and there is a limit to how much fuel the PCM will add and delete.

With HP Tuners he can force it into Open Loop and see how rich he has it. That is why it is there.

You can't with the LNF, it's not a standard GM ecu with a VE table. It has a wideband sensor stock, so it adjusts the trims so someone can adjust the maf table from the trims. There is no VE table for an LNF since its a torque based ecu.

Are all the bi-directional features gone?
Turning the fans and fuel pump on and off etc.

You still have fan control, but none on the fuel pump. Also no active adjustments (or whatever it's called) so timing and VVT adjustments require reflash. It's a Bosch ECU and supporting system similar to VAG systems