2001 LS bucks/ sruggles between 40-50 mph...

[BRUHA]

For some reason, my car bucks and struggles between 40 and 50 mph. The car runs smoothly between 0-39 and 51-max speed. It is only between 40-50 mph, that the car shakes and feels liek it is struggling to accelerate. I took it to the dealership, and they told me something about reprogramming speed calibration. Even after that was done, the car still does the same thing. Has anyone has epxperiences similar to this?

[cason1]

What year car, how many miles on it, when were the plugs and wires changed if ever?? Answers to these may help in diagnosis. Also, manual or auto tranny?

[ February 24, 2005: Message edited by: cason1 ]

[BRUHA]

It's a 2001 LS with about 65K miles (automatic tranny). Since I've had it (bought it in December 2003), none of the plugs or wires have been changed.

[MarkVa1]

I can't respond to the exact problem, but this topic has been dicussed in various forms recently on several threads. I would read the "Hesitation During Acceleration" thread recently posted. your problem sounds similar and this thread has lots of useful discussions about hesitation and misfires.

[andrewusmc]

I have the exact same problem and have new seals and plugs and COPs. This is deffinately some sort of transmission control problem. If I make a major throttle adjustment the car just downshifts and is fine. but minor trims in either 4th or 5th gear it feels like the torque converter just refuses to unlock itslelf so the the car bucks until the engine gets over 2000 or 2500 rpm. I plan on taking this probblem on soon. I have a company vehicle so rarely spend enough time in my LS to really notice stuff. But the slightest amount of imperfection in a car that perfect is incredibly painful

[andrewusmc]

I hate to referance another site. I never post just read. try posting this question on autoforum.com. I see the most proactive helpers from this site shareing info learned from other sites using their same web name from this site. great communication for our closed club of all special LS and Lincoln owners. Any anwers to any questions that can be shared here benifit us all.

[andrewusmc]

This problem is a form of torque converter shudder. the car needs to have the transmission and torque converter flushed and have the synthetic fluid used in the 2004 2005 recall on the Lincoln navigator. Dick heads were to cheap to notify the rest of the 5rn55 community. If you pay close attention this problem is almost not there at first. but about 20 minutes to 30 minutes drive time the temperature and vicosity of the fluit change and at low RPM in 4th or 5th gear (which are two gears this car has a locking device in the torque converter) the car bucks and shudders.

[Nick]

If you have to go synthetic, Mobil 1 ATF is the best out there.