Random Misfire when engine not under load.

[spuy767]

When my VQ35DE isn't under load, it misfires. Originally, I diagnosed and repaired a P1136 code by replacing the bank 2 camshaf sensor. The light went away, and it stopped misfiring. Now, the misfire is back, but only under minimal load, basically idle. If I accelerate, or run at a higher RPM, it goes away. But if I let it idle long enough to let oil get into the block ~30 seconds, the SES light comes back on but with just a random misfire (P0300) code.

[spuy767]

Update: I was finally able to get some freeze frame data and the Short Term Fuel Trim on bank 2 seems low, at least, it's lower than bank 1. Wouldn't this lead to a rich condition? O2 sensor maybe?

[maxnix]

Look at your O2 sensor's duty cycle on a scope.

Might well be time for new ones.

[SteveTheTech]

Update: I was finally able to get some freeze frame data and the Short Term Fuel Trim on bank 2 seems low, at least, it's lower than bank 1. Wouldn't this lead to a rich condition? O2 sensor maybe?

Nissans STFT is called ALPHA readings with a Consult they should average around 100% +- 25% either way. A drop in one bank many indicate a vacuum leak or weak injector or fuel flow. Check the lower plenum and plugs on the drivers side. Although a ton of things can cause this those are easier to rule out.

Scoping the H02S2s would be a good indicator, also if you have access to live data check you CAL/LD at idle with no load (ac,lights,radio all off) it should be ~20% +-5%.

Many stupid things can cause a P0300 and the modern VQ can through one of those for a number of reasons.

GL

[NJ 666]

I've seen a similiar scenario before. Is it possible that the timing solenoid is clogged,stuck,failed and advancing the cam at idle? That might be why it smooths out at higher rpm. The code you listed was for a solenoid issue not a sensor issue. depending on the logic of the ECM(I'm not sure what it is) It may not even look for another code if it sees a misfire. Scan the cam positions and the solenoid status.

Did you have this issue before the repair or just a CEL? If you replaced the solenoid(not the sensor) check to see that the gasket was installed correctly. I think that was the issue with one of them. Also the coating can peel off the solenoid gaskets and possible lodge into a passage.