OK, let me start with the basics. I just bought a 2006 Evolution MR from a private seller. The car had 6,900 miles on it. I got an oil change at 7,800 miles and now it has 8,800. The car has a boost controller and a new turbo back exhaust with a cat delete. It also has a new Walbro fuel pump. The car has been supposedly 'tuned'.

Now, I went to P&L Motorsports (they specialize in WRX Sti's but they have a Dyno and I wanted to know the car specs before I start adding onto it). So the car puts down 290 HP to the wheels and about the same torque. Everything went smoothly during the dyno.

Three days later (today) I get in my car and I see the dreaded 'Service Engine Soon' lit up. I take it to autozone and it throws code P0300 which supposedly means a cylinder misfire was detected, random cylinders.

I read that P0300 is common when someone tunes the ECU, anyone have any more details? I was planning on stopping by AMS and letting them deal with it -- but information first is better .

Thanks!

 

Check the plugs. and yes, P0300 is Random Cylinder Misfire Detected

 

Thanks, I will check them tomorrow. The car is running just like it did before the code was thrown. Any other suggestions I will check in tomorrow. Thanks!

 

Erase the code and keep driving. If your car is not breaking up at high rpms under WOT, then your plugs are most likely fine. P0300 is very common. I carry and scan tool in my car, that way if the SES comes on, I can check it real quick. I 99% of the time just erase the codes as I usually see the P0420 due to running a TP.

Good luck!

 

OK, funny follow up. I remember they (P&L Motorsports) took the spark plug cover off and hooked up some cables to the spark plug wires (I think). Well anyway, I remember they had trouble putting the cover back on and were moving some other cables.

Today, I popped the hood, jiggled some of the wires and the code disappeared. Something is flaky. I'll likely deal with it when I replace the spark plugs and wires at AMS.

Thanks for your suggestions.

 

they where just getting your rpm reading off the number one cylinder sparkplug wire. maybe it just had a bad connection or came loose and no one noticed.

 

Well they specialized in Subies .. probably couldn't handle the Evo . I would have gone to AMS (right down the block) but they wanted me to wait a week or so and well, a baseline dyno is a baseline dyno.

 

A "baseline dyno is a baseline dyno" as long as you use the same dyno. I can attest to the fact that P&L's dyno reads different that AMS'. I wouldn't worry too much about the P0300 it is just that a "random misfire".

 

Like they said, don't worry about it. That code's been a sore spot for a while. Just erase it and keep going. If it comes back again, there are a few "tricks" I've learned to tune it out, or there is a patch code for EcuFlash that disables the entire p0300 system check.

 

I have disabled my p0300 using ecuflash and mrfred's prephiery bits. I have not had the code in about 1000 miles. I do not get any studdering on the highway anymore. Search for disable test p0300