Flashing check engine light

Hello my name is Dave.

First thing we need to find out is what code is being generated when this happens. here is a link to our tutorial on finding the codes:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Keep in mind that the check engine light doesn't have to be actively on when you retrieve the code because the computer will store it. If you can retrieve the code and let us know what you find we will be glad to assist you in finding the cause. We look forward to hearing back from you and thank you for using 2CarPros!

Hello, this is Tom.

Here are the issues that can be the cause for your code it can be many things so we will have to go through to figure which is yours. Review this list of symptoms and causes and get back to us with anything that sticks out to you. Giving us an idea of how this began will help as well, things like any work done lately, Did this start all of a sudden or has it been a situation that was every once and a while that has becoming worse over time or have you gone to a different fueling station than usual. Pulling a spark plug to see it condition will give us good info on the burn and whether or not you due for a tune up.

Here is a good article for your review as well:

https://www.2carpros.com/articles/engine-has-low-power-output

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

P0302 Symptoms
Check Engine Light flashing
Rough running, hesitation, and/or jerking when accelerating
In most cases, there are no adverse conditions noticed by the driver
In some cases, there may be performance problems, such as dying at stop signs or rough idling, hesitation, misfires or lack of power (especially during acceleration), and a decrease in fuel economy.

Common Problems That Trigger the P0302
Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable)
Incorrect ignition timing
Vacuum leak(s)
Low or weak fuel pressure
Improperly functioning EGR system
Defective Mass Air Flow Sensor
Defective Crankshaft and/or Camshaft Sensor
Defective Throttle Position Sensor
Mechanical engine problems (i.e.†low compression, leaking head gasket(s), or valve problems.

Common Misdiagnoses
Fuel Injectors
Oxygen Sensor(s)
Powertrain/Drivetrain problems
Polluting Gases Expelled
HCs (Hydrocarbons): Unburned droplets of raw fuel that smell, affect breathing, and contribute to smog
CO (Carbon Monoxide): Partially burned fuel that is an odorless and deadly poisonous gas
NOX (Oxides of Nitrogen): One of the two ingredients that, when exposed to sunlight, cause smog.
Get back to us with what you have figured out
Tom

The first thing I would try is swapping the plugs from cylinder 2 to one next to it. Or if the plugs haven't been changed in a while change them all. If the misfire goes away you're done. Next would be to check the wires and cap for any damage or carbon tracking. If none of those work then the next most common issue would be a stuck injector poppet on the "spider" injector inside the intake manifold. The last item is one that seems to happen on the 4.3's when pulling hard like going uphill with your foot to the floor is that the exhaust valves can bind in the guides and cause a misfire. Usually if this is the reason the misfire will go away once the engine load drops off and it runs at a lower rpm for a bit. If your misfire is still missing (not just showing the code) then it is more likely the plugs or ignition parts. For the injector a heavy dose of seafoam cleaner in the gas might help free it, especially if you have been running ethanol gas for a while.

Higher fuel use and the misfire could mean the poppet valve stuck open on that cylinder. The white sounds like fuel deposits. A quick test would be to pull that plug, then start the engine and see if you get a heavy gas smell or mist coming from the plug hole. If you have access to a compression tester you could check that as well. That would show if it was a sticking valve or other mechanical issue, but I sort of doubt that.

Zero compression isn't good. About the only thing that would cause that is a valve failure or a piston. If you can get a borescope you could use it to look into the cylinder and see what is going on but first try backing off the rocker arms on cylinder two, if one of the valves broke it should show itself as you back off the rocker arm. They are not adjustable so putting it back together is just tightening them to 22 ft lb. Once they seat on the support arm. That should point out if it's a head or lower end problem.