P0303 1998 Ford F150 -

Question

Sparkplugs replaced 2 months ago, coils replace 1 month ago. Coming home from work it started to miss going up hill. Engine light came on, I floored it and it quit missing but runs rough while sitting at stoplight. I cleared the code and it was fine this morning but still runs rough at stop light.
VTS?
CSS?
CS?

Answer 1

Hi there,

I would check for an intake manifold leak to start with. With the engine running spray some carb cleaner along the intake and see if the idle smooths out. If it does, then it has a vacuum leak. If not then I would swap the #3 coil with the one next to it, just in case the new coil has failed. If neither change or prove to be the problem, it might be a good idea to do a compression test.