Just bought a 2013 interceptor utility a couple days ago, drove it back home about a 1.5 hour trip mostly 70 miles an hour, had no issues. As I got into town I noticed the tachometer needle bouncing back and fourth about 150 rpm, surging with a bucking feeling rather quickly. It seemed to happen through 2-3 and 3-4 mostly around 27-34 mph with light throttle, then it would shift again and the needle would stay put and the car doesn't seem to buck once it finally gets into the final gear. If I use more throttle I can feel the car hesitating, but the surging isn't as noticeable.
I did some research on different forums and tried a couple things.
While it was surging and bucking, I kept my foot on the throttle and stepped onto the brake with my left foot. The surging didn't seem the stop. Afterwards I was going about 30 miles an hour, (car surging) and clicked the OD off button on the end of the shifter. The RPM shot up to 3500, kind of surprised me that it must've dropped that many gears? Or that it dropped at all really, as I don't imagine I was in Overdrive doing 30 with light throttle.
Anyway, no check engine light came on the whole time this was happening. I was almost home watching the needle bounce and surge again and the car started shuddering almost like running over a rumble strip, and it was shuddering in sync with the tach needle.
The shudder brought back bad memories of a couple LX crown Victoria's I owned that had that common torque converter rumble in the mid to late 90's.
When I pulled into the driveway and put it in park I noticed a check engine light had come on, awesome I thought, I'll get my answer! It turned out to be P0430, a catalytic converter related issue. In my research I don't see how a plugged cat could be related to a shudder and rpm surging, but it does give me something to fix.
The car has 104k on it, and was department owned, the only service records I have are from the car fax and there's nothing relevant to maintenance. I am going to assume the plugs and coils and original and according to the maintenance schedule, should be replaced so I will definitely start there, but I am just wondering what you guys think my other course of action should be. Change the plugs/coils and just play it by ear? Bring it to a Ford dealer that can hook it up to a computer and watch the engine live? Get the p0430 code diagnosed and replace catalytic if necessary? I also see some people have had similar shudder issues go away after a trans fluid drain and filter replace. I'm really hoping the rpm surging, shudder, deal ends up being a simple faulty coil or worn plug that refuses to show up as a check engine code - I don't want to know what it costs to have a torque converter replaced at the stealership! So my plan is start with the easy required maintenance stuff and go from there, but I am certainly all ears to any suggestions from anyone here!
