Bought my 2004 X Type 3.0 automatic last summer at 143,000 miles. It now has 146,000. In the hot summer weather, not an issue or problem. Now that cold temps have arrived, I've noted a misfire/jerking that occurs just after the temp sensors allow lockup of the trans. However, it only occurs in lockup with a light load and light throttle and at speeds just above lockup (say 40mph or so). It has never missed at light load/light throttle at 50+mph. I may get just one miss or several and it doesn't occur all the time. No CEL has flashed or remained lit.

From a cold start and prior to ecm allowing lockup it doesn't miss. Once the engine is fully warm there is no miss. If I place the shifter in "4" (or "3" for that matter) there is no miss. if I back off the throttle or give it more throttle (not so much as to force a downshift or unlock the converter) the miss/jerk goes away.

It runs fantastic, has tons of power, gets 23+ mpg in my normal driving and idles so smoothly I can't feel it.

I've searched and found cars with somewhat similar issues but seemed that no one ever brought their thread to a conclusion.

So, my question is: is this a known transmission issue or is it something I should chase? I can easily work around this by running in "4" going up slight grades until the trans/engine are fully warmed. What I'm hoping to hear are responses that say "mine did the exact same thing and it was _________ (fill in the blank)". Given the sporadic nature of this problem, I'm not holding my breath for such an easy solution.

I will be doing plugs and intake gaskets in the spring. I don't know when the plugs were last replaced. I pulled the #1 plug nearest the front of the car and gap was in spec and it looked good. I know that is no test but at least I know the plugs still have electrodes! Motorcraft plugs are installed now.

I will be checking the frp vacuum hose today. My PCV hose is the correct type and I installed a new PCV valve when I bought the car. I've cleaned the MAF and throttle body inlet.

I have access to Alldata manual for the vehicle.

 

My 06 s-type is misfiring in cylinder 1 as well but only when I get on it hard. Just happen last night so I haven't had the time to examine it yet, but it probably just needs a tune up plugs and coil

 

What you describe doesn't really sound like a misfire to me, I have a feeling that you have a drive-train problem. Perhaps a bad tire that resonates at a certain speed. Or maybe a bad drive shaft, which in these cars go bad all the time.

Let us know what happens!