Random misfire assistance.

**SajoR** · 06-13-2012, 05:17 PM

Ok, I'm going to keep this short since I'm a little confused about this. So I got the P0300 random misfire code and I've already started looking up info as to what to diagnose. Spark plugs had been replaced not even 1000 miles ago before it started doing this. So I'm going to check wires, coils, fuel filter, EGR, everything that I've read up on.

It was misfiring pretty badly throughout all ranges, from low rpm to mid rpm. (never took it to high rpms) And it only does it after the car has warmed up.

Here's my issue, so I had to drive it last night and it was raining. Temperature was in high 60s or so, nice and cool and raining softly. The damn car didn't misfire ONCE. Drove perfectly as if there was never an issue. WTF?! Is it because of the colder, denser air? And if that's the case, could it be a malfunctioning MAF sensor or possible dirty throttle body? I'm cleaning these either way, but I just wanted to see what you guys think.

**az gt eater** · 06-13-2012, 06:25 PM

ALways, always clean the MAF first. Always. On to the misfire. I had that pop up once after the last time I had the intake out. I unplugged, and replugged the coil harness, and poof, the code's gone. It's an easy try, anyways.

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BTW, I really like Lubbock, one of my fav towns in TX.

**0rion** · 06-13-2012, 07:10 PM

like he said....start with the MAF. What are you mods if any? The fact it ran fine in rainy weather would steer me away from a spark issue because almost always a spark issue gets worse with moisture in the air. I would probably start at fuel or a sensor. That all goes out the window if you have and cam and/or stall. Both of those mods will set the random misfire code.

**SajoR** · 06-14-2012, 05:11 PM

I pretty much have all bolt ons as far as mods go, nothing done to the engine itself as far as cam/heads go. No stall either, just upgraded throttle body and air filter, long tube headers, no cats, full 3 inch exhaust all the way out and suspension work/supporting mods. And I didn't get a chance to clean it today, we had a crappy dust storm come through pretty much all day. But i'll definitely try tomorrow and see what happens.

And az gt eater, that's funny that you like Lubbock, cause I used to live in Phoenix, well Glendale area, and I love it there.

**JayTA98** · 06-14-2012, 05:39 PM

like the guys said get you a can of MAF cleaner and clean the MAF first. Do you upgraded your air filter to K&N or any kinda that requires oil?

**SajoR** · 06-14-2012, 06:25 PM

Nope I have an Amsoil air filter. When I bought it, it had a K&N air filter, but I replaced it with the Amsoil one. I'm not a fan of any kind of air filters that use oil.