Malwarebytes

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!

MR_Evo_Rob

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

Malwarebytes

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!

Muad

iTrader: (19)

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!

Malwarebytes

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.

wevo1985

iTrader: (10)

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.

Malwarebytes

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.

cfdfireman1

iTrader: (11)

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".

Slo_crx1

iTrader: (9)

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.

mt057

iTrader: (6)

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