When it warms up it seems the hesitation starts

DARRETT MCCASTER

MEMBER
1999 FORD F-150
4.8L
V8
2WD
AUTOMATIC
200,000 MILES

Good morning everyone, I hope and pray I can get some answers. I have the truck listed above extended cab. Truck with no check engine light on when I am driving it when engine is cold it seems to drive good but when it warms up it seems the hesitation starts. Now I just replaced fuel pump. Fuel filter. Fuel pressure regulator. No check engine light on at all my truck has coil packs not on the spark plugs but 4 pack section on both side of engine this is driving me crazy when engine is cold it seems fine but the more I drive it and the hotter the engine gets the worst it runs and I just replaced the PCV valve hose the one every body says is the main problem on these Ford's. I need some kind of direction to go in have anyone else had this problem and can coil packs and spark plugs get hot and go bad without throwing a check engine light. Please any help will be appreciated. Thank you all.

1 Reply

BMDOUBLE

MECHANIC
1,139 POSTS

Okay, I'm going to give you the quickest and easiest way to check this. First, pull of each spark plug wire boot at the plug and see what kind of spark you have. It should be loud and at least an inch long spark when you put it over a metal surface. Sometimes these coils get weak and will barely or not even produce a spark. If all of them look the same, while everything is reconnected, spray the plug wires and boots with water and look for any arcing out the side of the wire or boot, you should have someone power brake it also to put a load on the ignition system. If this does not show anything, remove the plugs and inspect the porcelain for cracks. There you have it, easiest to hardest but none of them are that bad! I always find one or more things wrong when I do this testing.

This guide can help as well

https://www.2carpros.com/articles/engine-hesitates

Check out the diagrams (Below). Please let us know what happens.

Images (Click to make bigger)