Intermittent Engine Misfire with codes P0300 P0303 P0305

rclarkbow

Hi guys,

2012 370Z Touring 163k miles

I've been dealing with an intermittent misfire since last fall. It has always occurred on either cylinder 5 or cylinders 3 and 5 plus the random misfire code P0300.

I first got a solid check engine light where the idle speed changed to 1000rpm until I erased the codes (this happened twice last fall, then it seemed fine).

The other day on the highway the check engine light was BLINKING on and off in sets of 5 and then eventually just went away and was fine. No solid check engine light after and I didn't clear any codes.

Took it to the shop and they scanned it and said there were no codes (no solid check engine light was on at this time).

Today it blinked again on the highway then went away after blinking like 2 sets of 3 times each.

Now codes were gone until I got a solid check engine light about a half hour later with codes P0300 P0303 and PO305. Same two cylinders.

Car mostly drives fine and I haven't noticed a misfire at all. The only other symptoms I can think of are:

-Sometimes engine seems to "skip" at idle like a small cough here and there
-When on the accelerator just enough to coast / using cruise control it seems to alternate between power on and power off kind of like the engine is stuttering / coming in and out several times per second.

Any ideas what this could be? Obviously I'm going to try to bring it back to the shop since they should be able to scan the codes now, but what do these symptoms suggest?

The issue started after the car had sat for 3-4 months without being driven much, but I've filled the tank 1.5 times since then over the last few months.