2000 ES300 Coil/Fuel Problem

[achates1]

Hi everyone,

I recently bought a 2000 ES300 at a wholesale dealer. It's a beautiful car, but it has a problem my brother-in-law and I are trying to figure out.

The check engine light and TRAC OFF light were both on, and the car was misfiring like crazy, especially at 40, 50, and 60 MPH. When we ran the scan, it said the coils were misfiring -- P0300, 302-306. So we replaced all six coils and spark plugs just to be safe. We were only able to get our hands on 3 genuine Toyota coils and 3 Advanced Auto Parts coils, but 6 Toyota plugs. We put the Toyota coils in the back and the generics in the front.

The lights went off, the car worked fine for a little while. While I was on the turnpike, though, I hit 80 and turned on the Cruise Control, and everything started again - misfires (not as bad) and the check engine/TRAC lights. Got the scan, and this time 300, 302, 304, 306, and a "System too lean" code showed up.

Questions:
- Is there a problem mixing Toyota and generic coils?
- Does the "system too lean" code indicate a problem with the oil control valve or fuel pressure regulator?

Any ideas? Last night the lights turned off and the misfires stopped, but I assume the underlying problem is still there.

Thanks so much,
Sam

[MR2Jedi]

Too lean conditions are caused by not enough fuel.
Things that can affect proper fuel delivery are: fuel pressure regulator, a clogged fuel filter, faulty O2 sensor(s), failing fuel pump, and clogged injectors come to mind.

Misfires can also be caused by inproper ignition timing.

[achates1]

Thanks for your reply, MR2Jedi. You were right on track.

For anyone else curious about this, the problem was the Oil Control Valve. Apparently on this car when the OCV goes, the coils on that bank misfire.

I replaced the OCV and the car runs great.

Cheers!