P0300 Random Misfire #2 and #7

'02 Camaro Z28 has been running super since I bought it. Has K&N FIPK and Corsa Cat Back exhaust. On the way to the shop for yearly inspection (can you believe it), SES light starts blinking, engine runs rough, exhaust smell. Code shows #7 lots of misfires, #2 half as much. Mechanic has now gone through most of the diagnostics - replace gas filter, clean all injectors, swap injectors, swap plugs, swap coils, replace Crank Position Sensor and did two relearns. He hasn't done a smoke test for intake leaks or a compression test because two cylinders started acting up at the same time. Does anybody have a clue as to what might be going on? It seems I would have a better chance of winning the lottery than to have a cylinder specific item like valve springs, coil, etc. on both cylinders fail at exactly the same time. Is it possible that a sensor (O2 or MAF) could cause multiple cylinder specific problems? Thanks for any replies.

Maybe the oil from the K&N is gobbed up on the MAF wires and they need to be cleaned or your O2 sensors might be taking a dump. Did he look to see what your fuel trims look like?

Wouldn't sensor problems cause misfires on all cylinders? My misfires are specific to #2 and #7 (next to each other in firing order, opposite each other on different sides of block, both at end of fuel rails). Although cylinder specific problems like valve springs, coils, etc. failing at exactly the same time would be a stretch.

P0300 can be a pain to diagnose. Maybe this will help if you haven't already seen it: www.gearchatter.com/viewtopic9365.php

Yes those two sensors can cause a 0300 code. I had it come up in mine and it after all the hassling, it ended up being the passenger side o2 sensor. But a 0300 code is a random multiple misfire, does not point to any specific cylinder. If you have it in 7 or 2, it would show codes 0307 and 0302.

Yes, that's why we ran scanner diagnostics - it shows 600 misfires on #2 and 1600 misfires on #7 (for a given period of time). I assumed a sensor malfunction would cause ALL cylinders to misfire not just two specific cylinders. That's what is so frustrating about this, that it's TWO specific cylinders not all, and that BOTH started misfiring at the same time!

Ok so then what you saw was the history. That means its not a constant thing, its coming and going in those two and not showing a pattern, hence the random code.

It shows no other codes? Not an o2 code or anything? 0300 is a PITA to diagnose when its all by itself, but it is almost always a sensor somewhere, and it doesnt make them ALL misfire.

The only time that I had a cylinder specific misfire it was a plug wire problem.

...but was it on two specific cylinders that started misfiring at the same time?

...but was it on two specific cylinders that started misfiring at the same time?

Don't get too hung up on that. They are next to each other in the firing order and the miss for 2 may just be a percieved miss due to the real miss on clyinder 7. ie, the comp may just be misinterpetating the info.

Plugs and wires would be the easy and cheap places to start. You could always try moving the plug and then the wire from the cylinders in question to another cylinder and see if the problems follow.

Plugs and wires would be the easy and cheap places to start. You could always try moving the plug and then the wire from the cylinders in question to another cylinder and see if the problems follow.

Ya he could, but hes not getting a cylinder specific code. If he was that would be a good thing to do for troubleshooting, but in this case he has something bad that is effecting multiple cylinders.

Ya he could, but hes not getting a cylinder specific code. If he was that would be a good thing to do for troubleshooting, but in this case he has something bad that is effecting multiple cylinders.

Would you please go back and read his posts. He states that it is cylinder specific to #2 and #7. And even how many counts each had.
Someone else said P0300 not him.

Would you please go back and read his posts. He states that it is cylinder specific to #2 and #7. And even how many counts each had.
Someone else said P0300 not him.

Nope, he said it, he even titled this thread with it. He never got a P0302 or a P0307. He said he has a P0300 and the scanner shows that it is happening in #'s 2 and 7. Its still a code P0300.