Topic: 2009 Tacoma 2.7l #4 misfire when cold

[JCBELWOOD]

I have a 2009 Tacoma 2.7l 4cylinder that is throwing P0304 (#4 cylinder misfire) ONLY when cold (less than 150 degrees).  The truck runs great at operating temp, & i can only duplicate the problem after it sets all night.  So far, I have replaced the #4 coil pack, all 4 spark plugs, cleaned all 4 injectors & fuel rail (swapped #4 injector to #1 when I put them back in).  Coolant is full, no bubbles in radiator, no steam or coolant coming out of the tailpipe.  Any help/ideas are appreciated.

[Willard]

What's the mileage? May need to do a leak down test on the #4 cyl....does that year have adjustable valves lash?

[emsvitil]

I'm thinking a vacuum leak that seals up once the engine warms up......

[Willard]

I'm thinking a vacuum leak that seals up once the engine warms up......

Very true. Get some carb cleaner and spray around intake and other mating surfaces and listen for idle fluctuations. Do it when its cold though. If you have a hand held scan tool that reads data you can also watch the O2S voltage for fluctuations 

[JCBELWOOD [OP]]

Thanks for the responses……..my scanner only pulls codes (cheap), but it did give me a #1 O2 sensor code today, i'll try carb cleaner when it cools off.