I just had the 90k service done on my 1995 SC400. At approximately 40 mph the engine starts surging badly if I hold the throttle steady. No check engine light comes on, nor does the bucking and surging change if I take it out of overdrive. I've had it back to the mechanic twice and he couldn't find a thing. Could this be a fuel pump delivery issue??? Of course it dosn't do it all the time, but it is getting more frequent and severe. Any good ideas????? Nitro

 

Anyone ever figure out what is causing this? I'm running into the same problem

 

I've been searching everywhere for some info. There were a couple threads where they talk about an issue with the torque converter, but it's pretty thin information. Have you checked for thrown engine codes? I'm gong to have to go take a trip to the dealership repair it looks like.... Nitro

 

throttle postion sesnor??

 

Hello,
The throttle position sensor sounds like the llikely culprit..even though it doesn't set a code....YET. This device is responsible for engine speed in all ranges, including idle, and talks directly to the transmission about the angle of the throttle plate, so thetrans can make adjustments.

It is very important, and sometimes sends warnings before it fails. Gaps in acceleration, weird idling and sloppy shifting are all symptoms associated with a bad / failing TPS. Kinda expensive, but worth it in terms of acceleration, gas mileage and the like.

 

I concurred that TPS is the issue here! Just got mine replaced! And what a different, the car runs like the day it came out of the dealership. I mean, Extremely responsive on the paddle!!! This will go from $250-$300 when you are done!

 

thats a heftly price you paid... the tps is around 130 and it should only be around 60 bucks to calibrate