98 ford expediton cylinder misfire after tune up

If your 1999 Ford F350 V10 gas engine is still misfiring after replacing the spark plugs and some of the coils, here are some additional steps you can take:

1. Check all the ignition coils: If some of the coils were misfiring, it's possible that the other coils are also damaged and need to be replaced.
2. Check the fuel system: Misfires can also be caused by problems with the fuel system. Check the fuel filter, fuel pressure, and fuel injectors to ensure they are working properly.
3. Check the air intake system: A dirty or clogged air filter can also cause misfires. Make sure the air filter is clean and replace it if necessary.
4. Check the vacuum system: A vacuum leak can cause a misfire. Inspect all the vacuum lines and connections to ensure they are tight and not leaking.
5. Check the timing: A misfire can also be caused by incorrect ignition timing. Check the timing belt or chain to ensure it is properly aligned and not worn out.
6. Check the engine compression: Low compression in one or more cylinders can cause misfires. Perform a compression test to check the compression levels in all cylinders.

If none of these steps resolve the misfire issue, it may be best to have a professional mechanic diagnose and repair the problem.

If your getting a P0302 ( cylinder #2 misfire detected), the first thing to check is the spark plug. If it's new then the next thing to check is the plug wire. If it has individual coils, then swap it out with another one and see if the misfire moves too. If so then the coil is faulty.

First off I think it's time for a new mechanic. Doing an oil change and replacing the fuel filter and air filter have nothing to do with a misfire. Spark plugs and ignition coils can cause a misfire, but a good mechanic will test the coil and inspect the plugs instead of just guessing. Your mechanic is guessing and just throwing new parts at the car. A misfire can be caused by (aside from a bad coil or plug) a faulty or clogged fuel injector, spark plug wire, wiring to the injector or a vacuum leak. Since you only have a misfire in one cylinder, and you hear a whistle on acceleration, I would suspect a leak in the intake manifold. Go to a reputable repair shop and have them check the manifold for leaks. You can also check yourself by buying an automotive stethoscope, and moving it around the perimeter of the intake manifold listening for a hissing sound. Or have someone press on the gas while listening for a hiss under the hood.

P0303....Cylinder 3 Misfire Detected

P0304....Cylinder 4 Misfire Detected

sounds like a new set of HT leads and plugs wouldnt go amiss(fire wires) weird name that fire wires HT stands for high tension leads in proper english .

Tuned-How -Spark plugs??

You have a misfire, you say on #3,
that isn't a plug issue

Have you tested the ignition module

Have a scope put on secondary ignition,
so you don't keep throwing parts at it

fuel pump....if its got a spark, and the valves are timed... check the obvious...air and fuel.

most likely the coil or ignition module

Replace the coil for number 3 cylinder.

It could be the coil, or the ignition module where there coils sit on. Start with the simple and check the spark plug wire first, then work your way to the coils and module. Once you work your way to the coils, try switching the coils around and see if the misfire will switch cylinders which would indicate a bad coil. If the same cylinders are still misfiring after the coils have been switch, then it's a good chance that's it's going to be the wire harness to the ignition module or the module it self. Good luck and hope this helps.

Could be bad coils, or someone switched the two wires if it has wires.