My 2001 2.7 has been throwing p0300 & p0303 (misfire) codes for the last couple weeks. Here's what I've done so far.
Replaced fuel filter.
Checked plugs - ok
Swapped coil packs - no change
compression test - #3 about 5% off but within limits
Leak down - slight leak in #3, no bubbles in rad, no noise in oil or exhaust!
Seafoamed in break vac line - lots of white smokeand ran a bit smoother.
Bottle of Seafoam in current tank of gas.
What's next? I'm thinking injector swap, but I guess I need to find o rings.
Maybe sticky valve? Idk there. Bad Cat?
any help appreciate!
I have now cleaned the throttle body real well.
Added some seafoam to the crankcase.
Replaced the fuel injectors
Replaced spark plugs (denso oem, .043 gap)
All the above with no real noticeable improvement, though a bit more throttle response. A p0303 code will still come on, sometimes at a cold startup. A flashing CEL will happen under load conditions such as climbing a grade.