Q: Car throws code: P0301 even after I have changed spark plugs, fuel injector, fuel filter, ignition coils.

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I bought my 2008 Ford Escape in April of 2016. It had 102,000 miles on it when it was purchased. There was no check engine light on for the first month or so. After about 1 month it threw the code P0301 however it didn't misfire once the was warm, it just had a rough idle for the first 30 seconds upon cold starts. After 30 - 45 seconds the idle would smooth out. I didn't know milage on spark plugs so I changed those. It fixed the problem for about 2 - 3 months until the light came on again. Same code. This time I decided to change the ignition coils but the light came back on after a couple days. I decided to change the fuel filter and the fuel injector for cylinder 1 and the light stayed out for about a day. I did notice that the Intake manifold had a lot of residue buildup on the inside. I'm not really sure what to try now other than an intake cleaner.

My car has 106000 miles.
My car has an automatic transmission.

The engine intake near cylinder one should be checked when first started to see if there is any vacuum leaks at intake gasket or the injector O-ring.

If no vacuum leaks are found then you may be having a carbon build up on the intake valves. This can cause running rough and misfires when cold, and go away as the engine warms. The carbon on the valves will suck in the fuel when it is cold and starve the cylinder of fuel. As the carbon and engine warms up, the carbon gets saturated with fuel and then the cylinder gets all the fuel it needs.

Try getting the combustion chamber cleaner from Ford and run it through the engine. Start doing this when it is cold so the carbon absorbs the cleaner. After that’s done, let the vehicle sit for at least 30 to 45 minutes. Then run some more cleaner into the intake and then let sit again. When adding in the cleaner for the third time, let the cleaner run in the intake and then hold the RPMs at about 2500 RPMs for a few minutes then rev the engine about 5 or 6 times from idle to 3500 rpm or as high as engine will go before the RPM limit engages. Road test the vehicle after clearing any codes caused by this cleaning procedure and then you should be okay.

If you feel like you need some assistance with this, consider YourMechanic, as a certified professional can come diagnose your Check Engine Light firsthand and perform this procedure for you as necessary. Good luck.

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