I've got a 2009 ford ranger and the other day I was driving it and all of a sudden it started shaking bad at highway speeds. At first I thought I had a tire going flat then i thought a wheel weight came off when the low tire light never came on. I pulled over and it definitely felt like it lost a cylinder. It never died but it was running terrible at idle. I was on my way to work so I had to just limp it there it would shift to overdrive at 60 but if I tried to do 65 it would downshift and run over 3k rpms. No check engine light ever came on. I made it to work and went in and I thought I might need to get my wife to pick me up so I went back out to see if it would start and it fired right up and idled fine, drove it home and back to work today problem free. That's 100 miles I've put on it since and it's been fine. Our fleet at work is ford so I had one of the Ford mechanics hook up his computer to it and it passed every test and had zero codes. The truckis still under warranty but ford won't do anything with no issues when I bring it in but I hate to get stranded somewhere.

All I've done to it recently is a transmission filter change and drain and fill. I put a new fuel filter on it last night just to try and eliminate that. I'm gonna throw a new set of plugs and wires and maybe a coil pack on it but that doesn't seem like it would be as intermittent a problem. I pulled on all the wires and rubbed all over them with it running and nothing changed or shocked me. Anybody have any other ideas what it could be?

Also the auto parts had 2 different motorcraft plugs for this truck which is correct sp439a or sp439?

 

Could have been torque converter lock up acting up

Torque converter is a "clutch" of sorts, the computer has the option of releasing or locking it
When you are stopping computer needs to release it or engine would stall, but when driving you get better performance and MPG when it is locked.

Since you just change the trans fluid you could have got some air pumped in to torque converter, air can get trapped in trans cooler or upper trans areas, it will get cleared out over time.
If torque converter can't fully lock, it will shutter as it slips, same as clutch can shutter if it slips and grips.

Since there were no codes and all seems well now, there is not much you can do but guess at possible problem.
Which is what the above is, a guess.



You can use either spark plug, the "a" usually denotes Suppressor type spark plugs, if you are getting Radio noise from spark system then use "a" model, if not then regular is fine and usually less money

 

Thanks for the reply. Yea I know it's all guessing I was just trying to think of other things to look for as a possibility. One thing somebody said was possibly water in the fuel and when I stopped it had time to separate or evaporate out of the cylinder.

Hopefully it doesn't do it again. I bought this truck with the idea of the 2.3 being a dependable motor I was hoping to at least get 200k out of it. I try to do as much maintenance as I can to keep this thing in shape.

Man maybe I should have got the a plugs.... I don't have some radio interference. I don't know if it would help with my phone charger making the radio static. I think I need the ground isolator for that.