Misfire in Cylinder 4 only when cold

Hello all, I recently bought a 2007 Toyota Tacoma 4 cylinder (2.7l) with 143,000 miles on the car. I notice that the car hesitates a small bit on a cold engine and within a week I get a cylinder 4 misfire (P0304). The misfire only happens when the engine is cold. I'd replace all the spark plugs with factory plugs and did notice that there are a lot of carbon build up inside cylinder 4 and on the plug. The insides of the other 3 cylinders and plugs looks clean. while I replace the spark plugs, I also switch the coil packs from cylinder 4 to 3. In addition, I add 1 can of Seafoam to the gas tank. Again, within a week I get the same misfire on cylinder 4 (P0304) and again only with a cold engine. When the engine warms to normal operation temperature, the car runs smooth and responsive and never throws a code. so what is wrong with my truck, and why am I having problem with a cold engine? Any feedback will be greatly appreciated.

 

Swap your injector from 3 to 4 and see if you get a p0303 instead. If it still is on 4, perform a cranking compression test and update with the results of cylinder 4 as well as another cylinder to compare it to. Not much can cause a misfire- ignition, injection, or base engine.

 

If the code doesn't move when you swap injectors, focus on a spark problem. Did you replace the wires?
IIRC, there are two coils. Since each coil fires for two cylinders, you would have a misfire on two cylinders(if it was the coil causing the problem).

 

That was what I was going to try next is swapping the injectors. well do a compression test after

 

I've had about 4 to 5 misfires in the past 4 weeks and all were on cylinder 4 (P0304) and all were during a cold engine. I'll double check the wires as well.

 

check to see if your coolant bottle is low.with the mileage you have it could possibly be the head gasket.if you have accses to a gas analyzer take off your coolant cap and sniff your rad.you want to look for high hydro carbons.
another way to check is to put your cooling system under pressure remove your spark plug and look into your cylider with a borascope and look for coolant.hope it doesn't go this far and is something simple

 

A compression test with the engine cold would be my first step. If the compression is good, and no coolant is found in the cylinder or being burnt, I would swap the #4 coil pack to another cylinder first. If the misfire follows the coil pack, then replace the coil pack. If the misfire remains at #4, I would suspect the #4 injector.

 

A compression test might tell you something is wrong, but a leakdown test will tell you exactly what is wrong. The tester is about $44-100 depending on quality. You will need a compressor, and a socket to turn the crank to make it work.

 

Thanks fellas, I will get the compression check and report back. My fear is the beginning of a blown head gasket.