alright im in a tight jam here and any help at all would be HIGHLY appreciated. i have recently bought a new truck this month and everything was nice and dandy till i noticed an annoying jerking at 45-50 mph. the check engine light didnt come on till recently when it got really bad and would barely start. i hooked a code reader up to it and it said cylinder 6&8 misfire. so i had the coils replaced on those two cylinders and it seemed to start and idle better. so i took it on the interstate to see if the jerking was gone as well. and it still jerks at 45-50 just like before. i was going to take it to the dealership to have them figure out what the issue is but thats 100 bones just to figure out what the problem is. my mechanic doesnt want to mess with the spark plugs because he knows they always break. so i decided to see if anyone on here had an idea on the issue, any help is appreciated.

 

It's the spark plugs. Mine was doing the same thing, when it wanted to shift into OD. I had all 8 plugs changed, 5 of the plugs broke in the hole. I also replaced the coil packs on the back 2 cylinders. Have fun!

 

I agree. That's a low grade missfire and it probably won't show on a scanner and even if it does it may show incorrectly.

Plugs and coil packs.

D

 

when i test drove my new-to-me truck it did the exact same thing; as part of the deal i had the place do all 8 plugs and it hasn't done it once in three weeks of owning it.

 

This must be what is happening to my 2006 F150 XLT 4X4 with 94,500 miles on it. When I am cruising at about 40-50 and start to go uphill when I accelerate it hesitates, lurches and then takes off fine. A week or so a go on a two lane road I went to pass a semi and when I accelerated there was like a 5-10 second delay. Then takes off as it should. No idiot lights come on, I have not had it scanned.

Seems I am about at the spark plug change mileage anyway, so I hope that is the fix for me, too.

 

Well to start with, they don't always break. When I decided it was time to change the plugs (2006 Mark LT 4x2, 5.4, 35,000 miles) with the Motorcraft SP 515’s, although I did follow the most recent TSB, I also relied on my experience back in the 1970’s when aluminum heads & intake manifolds were just entering the street scene and never-seize did not exist. Here are the exceptions to the TSB that I did…
1. I ran Lucas fuel injection cleaner, mixed at 3 times their recommendation in 1 full tank of gasoline. Purpose…if I was lucky, it would dissolve or loosen any carbon buildup (although many do a real fuel injection cleaning also- and it is probably a best practice to do if you have more than 45-50,000 miles on the plugs)
2. Although I am a fan of PB Blaster, I used a product called ChemSearch “Yield”. The issue I have with using carb cleaner is the lack of lubrication…..in the old days of removing steel plugs from aluminum heads, we use to mix up acetone & ATF…or of we needed more lubrication, kerosene & ATF, “Yield” provides this lubrication- much better IMHO than even PB Blaster.
3. Yes, I put anti-seize on the plug threads (I know the TSB says not to)
4. Of course…a lot of patience, I really doubt if I ever put more than 20-25 lbs of force during removal (purposefully)
The end result, only one plug even “squeaked” coming out (but it basically unscrewed like a regular plug- literally). Plug #4 was initially a little stubborn, but after the second try, then waiting about 30 minutes, it came out with very little effort…just kept wiggling the plugs (tightening/loosening) by 1/8th or even less of a turn- and they all came out without a single one breaking or any issue really. Another technique that can definitely be used is to loosen the plugs about 1/8 to ¼ of a turn, start the engine for about 1 minute- this allows the flame to travel up around the plug to burn off the carbon, let cool, then remove with the process I previously described.
As far as using an air ratchet, I can understand the theory of “shocking” the carbon loose, but I have also seen and experienced in my younger days some real disasters.
Actual working time: 2 hours…..including washing my hands, total time was 5 hours.

 

Did this fix your problem? I'm having the same issue, and afraid its my torque converter. But changing my plugs this week, hoping it fixes the problem.