My engine, a 5.4, just started having a really bad hesitation or shaking whenever I try accelerating! It runs fine when it's cold but after it warms up, that's when the shaking starts. When idling at a stop sign, it shakes like it's going to quit till I rev it up. It really shakes bad if I'm accelerating on an incline. It has 131,000 miles. I had all 8 spark plugs the two back coils changed 10,000 miles ago. Fuel filter changed 6,000 miles ago. I've been pouring in 6 oz. of Lucas fuel injection cleaner at every fill-up. I know I have two O2 sensors bad but that shouldn't cause the engine to shake. Engine starts easy. Diagnostics at a Auto Parts gives a code left and right banks are lean as well as the code for the O2 sensors. Any thoughts?

 

I just had all of those codes and it turned out my o2s were fine but my intake manifold gaskets were leaking and causing all of the problems. This problem could easily lead to blown coils causing the shakes too.

 

Which O2 dtc's do you have ? Has the check engine light ever blinked then shut off again? Well I guess you wouldn't know since it's always on would yuh lol.

Might as well not change the O2 sensors, since it's running this way anyway. You'll probably just fry a couple new ones pretty quick. Although I would check your connectors and wiring.

So which spark plugs did you use. Yea try to specific if you want to figure this out. So far , your not specific enough.

Sounds like a definite ignition problem, -without more info, who knows what's causing it. Fuel delivery, EGR, Coils, plugs. No Lucas stuff for these injectors, - use Techron. I doubt that's the problem, it's just much better stuff.

 

Turns out the #4 cylinder ignition coil was bad and a vacuum line had a hole in it and that took care of the "check engine soon" light. Truck runs good. What's next to go wrong now?

 

All kinds of success stories today...

 

Glad you got it fixed.