Random misfire, should I just disable it?

[pHEnomIC]

I keep getting the p0300 on a ls1 w/ torquer v3 cam (231/234 .644/.598 111lsa). Car runs great and I never notice any running problems. The code just randomly pops up and usually goes away. I checked plugs,wires,o2 sensors, etc. I recently broke some valvesprings and replaced them and inspected all valve springs. I really cant think of anything else that would cause it. (It is possible i have damaged valve or something).


Should I just disable this code? It is getting on my nerves and I can't diagnose it. I desensitized the misfire detection at idle but it still shows up.

[WS6FirebirdTA00]

post your tune, I never get this code with my cam, which is similar as well as the Trak cam.

[pHEnomIC]

Here it is.

[WS6FirebirdTA00]

what is your idle AFR? What plugs are you running and what gap?

[C5 2000]

Yor power-Hop inj disabled value set to (0) why? you disabled the cylinder.

[pHEnomIC]

idle afr fluctuates 14.7 to slightly leaner than 14.7. Id say to 15.5 range. Tr-6's gapped at their stock gap (i think its .38) but i checked em all.

I will look into the inj disabled value. Where is it at? I never recall changing it.

[WS6FirebirdTA00]

Richen it up. If you aren't spraying, a TR6 may be too cold for the low loads. I run a TR5 in my car at about 0.040" (same as the TR55, but tighter gap).

Power hop is an ETC control, it does absolutely nothing in this calibration.

[RWTD]

Curious, are you tuning in SD/VE mode only? What's the reasons you set your P0101, P0102, and P0103 all to "0"?

Also, not that it matters, but just set the EGR Enabled back to "Disabled", and change the Disable/Enable Speeds back to stock. No reason to change things when they are already disabled.

I'd definitely suggest richening it up at idle, as well. With aftermarket cams, the valves are open longer, therefore the fuel mixture becomes unstable in the cylinder, and potentially too much natural EGR is being introduced.

Are the misfires just occuring at idle, or everywhere? If you still are getting the misfires, I'd change both the "Medium RPM" tables up to 4000 rpms to 32767, as well. If that doesn't work, then just set the Mac ECT to -40 and the Min ECT to 284.


C5 2000, he didn't change it. It's the stock value. As WS6FirebirdTA00 said, it doesn't apply anyway.

[pHEnomIC]

I have egr enabled because I use it to log my wideband. I have never had a problem in the past and it has been like that for over a year. I made sure to zero out any related tables.

What is the best way to richen up idle in closed loop? As I understand it, no matter what I do, it will relearn 14.7.

How about decel, does my tune look ok on decel? I really don't know if i tuned that correctly. According to the wideband, it seems to go lean from dfco on decel and then itll go a little rich for a split second before settling at commanded (seems correct to me).

One other possibility that I notice is: If i bring my engine to low rpms by dragging it below idle (6 speed), often times it feels like the engine stops for a split second even when given gas. I think that might be a misfire. Anything in my tune that might cause this? However, I rarely do this and I still get the code a lot.

[pHEnomIC]

I made a good log of the misfire data. It appears that cylinder #1 might be misfiring more than others. Leading me to think that something is going on with that cylinder. Can anyone look at it it and tell me for sure? Or is something else going on?

It appears to only happen at about 1500 rpms as well.

PIDS:
WB A/F ([PID.2811]*2)+10
WB A/F Error 100*((([PID.2811]*2)+10) -[SENS.121])/[SENS.121]

[WS6FirebirdTA00]

you can adjust the switch points

[pHEnomIC]

you can adjust the switch points

Ok that's what I thought. I don't quite understand how the switch points work even with looking. Can you explain how i should adjust em and by how much to start with? Does increasing them make it leaner or richer?

[WS6FirebirdTA00]

Increasing will make the switch point richer.

[pHEnomIC]

OK little update. I've played around with switchpoints a bit and it seemed to throw off other stuff that was working well.

I've tried to eliminate variables. Ive swapped all the following individually and nothing moved the misfire: coils, plugs, plug wires, injectors, rockers. Pushrods and valvesprings are good.

For some reason at idle now, all my cylinders are missing evenly. (although it idles just as good as ever). So im not worried. This might be a fueling issue due to resetting fuel trims or something. I still get to 1500 rpms and cylinder #1 will misfire like crazy. The number will shoot up to like 50 misses in a few seconds.

It seems that both banks trim evenly with ltft and stft so I don't think bank 1 is really even getting affected by the misfire. I am noticing a slight stumble at 1500 rpms though.

Any other ideas? I am gonna try to play around with the scanner and see if i can fix something through it.

[Atomic]

I know this is old, but did you ever figure this out? I have the same condition on my 04 5.3 even after new plugs and wires.

[Atomic]

LPP gt2-3 cam (207/220, 571/578 118), long tube headers, intake, LS6 springs, hardened pushrods. I havent changed anything in 6 months then one day this issue pops up.

[elzarra]

this could be caused by a vac leak on intake. or maybe a loose crankshaft reluctor wheel or contaminated crankshaft sensor.

[Atomic]

I had to change the extension on the tune .bin for it to upload, so just change it back to .hpt and itll be fine.

Mine only misses at idle, any other time its fine.

[Atomic]

...letting them inject?.... I haven't touched the actual injectors or their parameters in the tune, and yes they are stock injectors.