Hello all,
I need advice from someone out there. In the last year my check engine light has gone on and off. It has always been P0300 - Random Engine Misfire and no other codes show up. I have replaced the Fuel Pump, Belt Tensioner, Spark Plugs, Plug Wires, and the Coil Pack. The idle is rough and the light usually goes on when I'm on the highway and sometimes when I start him it usually is not quick to turn over. Im running out of ideas and patience, does anyone else know what it might be??

 

What is your fuel pressure at idle?

Compression numbers?

Is the timing cassette in time?

Check for vacuum leaks?

MAP sensor operation?

Crank/cam signals?

 

Some other areas to check: https://www.obd-codes.com/p0300

 

Hey,

I just dealt with this on my '05 R50. That code is a little vague.

Here's what I did-
1. Replaced my spark plugs, wires, & wiring harness (inexpensive).
Light came back on.
2. Checked my compression, cleaned intake (inexpensive).
Light came back on.
3. Replaced Serpentine belt and Harmonic balancer (not cheap).
Light has not comeback on.

Tuns smoother, quieter, and I'm at 100k miles, so I chalk it up to my 100k tune-up. Hope that helps.