Skips on cold start ups (1 Viewer)

Dec 24, 2007
Charleston S.C.
Thougt I'd share some insight on an issue that seems to becoming more common on the 4.0 4gen 4runner.
Vehicle has been used under normal conditions, no offroad use, no towing, no past or present overheating issues 135xxx miles
Vehicle condition is that it has a slight skip on AM. starts or after sitting for a while. Skips dissapears several seconds after vehicle is started and runs fine thereafter. The check engine light eventually illuminates and shows codes po300, and po306. After performing compression test, changing spark plugs and moving the injectors from the left side of the engine to the right and vis versa. The same condition still exists. The compression test did not reveal and significant difference between cylinders all between 165 and 175 psi.
Using a boroscope and visually inspecting inside the cylinders through the spark plug holes, there was an obvious wetness on top of cylinder #6 piston. Pressurizing the cooling system with a hand held radiator pressure tester and allowing vehicle to sit overnight revealed a coolant puddle on top of the #6 piston.
We are in the process of removing the engine and replacing it with a used low mileage engine as this was the customers wish.
He did not want to try to repair the existing engine but I will definitely remove the cylinder head and try to determine the root cause of coolant entering #6 cylinder.
All aluminum head and block engine will most likely not be just a blown gasket issue.

Will post pics of disassembled engine when we get to that point.
Aug 2, 2009
Illinois and Alaska
Lots of complete failures of these motors are starting to surface - relatively compared to the 2UZ.

The V6 is no comparison for the bulletproof reliability that the V8 has demonstrated since 98.

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