Bumping while acceleration

[UVBNHAD]

I have an 04 GT and I've noticed that ever once and a while while accellerating in third gear around 1750-2200 RPM the car bumps slightly. I say bumps because that's the only way that I can describe it. I don't think that it happens in any other gear but that's not to say I haven't noticed it. I'm not sure if it's something to do with the engire or possibly transmission. This is my second engine in this car as the first one was a factory defect. I'm thinking that the tech that put the new engine in messed something up with the aligning of the clutch/tranny/engine. Ford says that there is nothing they can do at this point because I cannot "recreate the bumping on demand" as they put it. I guess they use the mentality that it has to break before they fix it. Any ideas?

 

[hotmustang331]

Mine jerks a little in 1st at around 1100 RPMS with just a little gas...dont know about yours, except that they could have flashed the computer or something and put a little more timing, but you would be pinging on 87, then you would no that was your problem.BTW what exactly was wrong with your 04 GT motor the first time?

 

[UVBNHAD]

The engine was missing extremely hard on the number three cylinder after approximately 2000 miles. They replaced the head but that didn't do anything for it. The day I got it back from the dealer it started again so they ended up swapping the whole engine. Apparently they even had the engineering team from Dearborn come down and investigate it but they really couldn't find anything.

 

[Mossberg]

mine bucks in 1st sometimes at very low rpm (not stalling though) when coasting.