i blown a spark plug about a year ago and had to replace the head. the shop i took it to mess up the other head and replace it for free. when i got it back it ran fine. till about a mouth ago. it shakes at a stop and when i get up to about 50 to 55 mph it shakes. also it shaes bad with the ac on at a stop. Also when I'm pulling my trailer up hill it hesitas to get up the hill. before it had no problem. the engine light says that cylinder # 1 or #8 miss fire and egr insignificant flow. i replace the spark plug and coils that need to be replace. the egr is also new. could it be a bad injector. It a 1997 e150 5.4l today I notice a hissing noise when I let off the gas. Please help, I need my van back.

 

Read my post here;

https://www.ford-trucks.com/forums/8...l-problem.html

 

It now shift 1st and 2nd hard. And it take a couple of seconds to down shift, even then it feel like where barly moving. I service the transmission like 15,000 mile ago. Every thing was good till it started misfireing. Please help.

 

It sounds like there is more than 1 problem with your engine. First check all of your vacuum hoses and connections in the engine bay, especially the elbows for the PCV, the 1 on the back of the intake manifold is the most common right in the middle of the bend.
See what you have and get back with us on what you find and we can go from there.

 

I fix the engine light. It was the egr vacuum pressure sensor. I replace it and now it idles good and shift better. But shakes still at 50-55. And I still am looking for the air leak. I also check the vacuum lines and the PCM line. They are clean and are in good shape

 

I am having some of same troubles.F-250 SD 2003 144000miles. Dealer thinks I need Long Block. Help if you can.