So I have been trying to diagnose the problem in my truck for awhile now and I am wanting to hear your guy's input on it. Truck runs great at all speeds, idles great, the whole works. But, if I am on the freeway, driving around 60, and attempting to go up a hill or the truck is under a load, the truck shifts down and is cruising around 1400 rpm, and I begin to lightly accelerate without letting the truck shift back up to the overdrive gear, the entire truck will shake and shudder. As soon as you can get it to shift up, it immediately goes away. From what I have read, a lot of people have misread a transmission problem for an ignition problem. i.e. losing a cylinder causing the truck to shake. But, the only problem I see with this, is wouldn't you see this misfire across the board? I mean shouldn't I be able to get the truck to do the same thing in a different gear?

Perhaps I am being fooled and it is indeed a ignition problem. It just seems strange to me that I can't get it to do it anywhere else. As far as I know, the plugs have never been changed. I have a new set in my toolbox but haven't had a enough time to change them out yet. More than likely I will bring the truck in to have them changed just because I don't want the headache.

 

Change the plugs. You have what's called a low grade misfire. The plugs are too worn out to fire a very lean mixture. Use only MOTORCRAFT plugs.

By the way, you didn't tell us year and engine, and how many miles.

 

The spark plugs need changing.

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Info on the truck I.E. Miles yr, engine? But from what you are saying +1 on plugs and or COP's. I just changed mine out last yr along with COP's with autolites platinum plugs. I was having similar issues and now they are gone. Dont torque to or use anitseeze on the plugs. I believe the correct torque to prevent the plugs from blowing out is 28ft lbs. Someone jump in and correct me if im wrong. I know people say only use Motocraft plugs but I always had great experiance with with autolites, only the platinums though but you definetly cant go wrong with Motocraft anything. Just my .02cents.

 

I bought the OEM Motorcraft spark plugs from Ford. I really just don't want to to do the job...maybe I'll pull it in this week. Thanks for all the feedback!

 

Its really a simple job. Just be patient and I found having swivel sockets really helped if you decide to do the COPs. Shouldnt take no more than 1-2hrs depending how many beer breaks you take.