I have a 2001 ford f150 2wd v6 4.2 with 130k on it. I have a slight rough idle and it hesitates bad at low rpms. It was just recently throwing codes for misfire on clds 1,5,and 6. I have recently replaced the following in my quest to fix this problem. fuel filter, plugs, wires, coil pack, crank position sensor, camshaft position sensor, mass airflow sensor and the egr valve and o2 sensors were replaced this spring. I have also measured my vacuum pressure and it was well within specs. I did a compression check and tested the fuel pressure, both of which seem fine. I have a data logger attached and it seems to hesitate the worst when the advance is at a value below 10. I am pulling my hair out and any assistance would be greatly appreciated.
The problem might be with carbon deposit build-up on the backsides of the intake valves. When enough carbon forms on the valves it can act like a sponge where it absorbs some of the fuel that’s supposed to be introduced into the cylinders. Incorrect fuel mixture can cause rough idling and misfires. So you might try a decarbonization of the engine. Here’s how to do it.
Purchase a can of SeaFoam Engine Treatment. Get the engine up to operating temperature. Turn off the engine and remove the vacuum hose from the brake booster. Adapt a hose that will fit inside the end of the brake booster hose and into the bottom of the can of SeaFoam. Take a pair of pliers and pinch off this hose. Have someone start the engine and bring the idle speed to about 2000 RPM’s. Now slowly open the pliers so the SeaFoam begins to be drawn into the engine. It’s here where the throttle is manipulated and the pliers are opened and closed to prevent the engine from stalling. Once all the SeaFoam has been drawn into the engine, shut the engine off and reconnect the brake booster hose. After a half hour has passed, restart the engine and bring the idle back up to 2000 RPM’s until the smoke from the exhaust clears.