99 Toyota 4 runner 3.4 Liter, Code P0302

by Mark
(Escondido, San diego, Ca.)

The runner is throwing po302 code. I've changed the spark plugs. Today I switched the #1 coil pack with #3 coil pack to see if the misfire followed it, it did not?
I sprayed water on spark plugs tonight to look for arcing and saw none?
please help

99 4runner 4x4 3.4 sr5


Answer

Hi, Mark! There are a couple things that you need to do to narrow this down. The first is a compression test on the #2 cylinder as well as one or two of the other cylinders. See if the #2 cylinder is lower on compression than the other cylinders. It sounds like you have done some good tests to check parts of the ignition system. You should switch one of the spark plug wires with the #2 wire. This will tell you if the wire is a problem. If the spark plug wire is bad it can be hard to tell so definitely try this test. If you still don't find the problem then you need to switch one of the fuel injectors with the #2. This will tell you if the fuel injector is to blame. You want to do everything you can to figure out if it is something easy before you get to the things that are harder to fix!

Whatever the problem is with this type of code (or similar codes like p0303, p0301, p0304, p0305, p0306, etc.), it is something that is isolated to that one cylinder, keep this in mind as you are working on diagnosing it. Remember that a cylinder needs fuel, spark at the right time and compression in order to fire.

Some other things that it could be that would be harder to fix are a bad head gasket or bad valves. These engines have a problem with bad valves so that could be a problem with your number 2 cylinder. You can check this by doing a cylinder leak down test. You can buy one from my Store. This test will tell you if you have faulty piston rings, valves or head gasket.

If you just want to check the head gasket you can get a cylinder head gasket leak tester. This is a tool that will tell you if you have exhaust gasses leaking into the coolant. You can also buy it from my store. It works great and is simple and fast to use, I have used it many times.

Good luck with your car problem, and remember the simple stuff. Don't give up. Thanks for contacting me.

-Steve