LS400SLAMM

I have a UCF10
When I gas it not fully depress it lags then it pulls hard (sorta like vtec) or vvti but this motor is non vvti Car is Stock no mods nothing does this sound like a bad trans?

Scraape

sounds like check your trans fluid level and/or condition of current fluid

JetCat

Hi LS400SLAMM ... personally I am pretty big on doing transmission servicing .... as well as watching what the fluid level is ... if there are any leaks going on ... etc etc etc ... there is a very well produced video on this topic done by ChrisFix (on YouTube) .... the guy did an amazing job making this video ... anyways ... this might give you some insight in as little as 10 minutes .... perhaps this may lead to an answer ..... hope it helps

LS400SLAMM

Hey @Jetcat I appreciate the feedback but All fluids are changed regularly at 4-5k I got the right term its throttle lag but now i have to figure out how to fix that

Superfast1

I had the exact same problem on my 97 LS400 w/ 240K miles even though I have drained & re-filled my tranny w/ the recommended Toyota Type IV tranny fluid at every 25K miles interval over the past 20 years. If yours is high mileage & the tranny hasn't been serviced then your torque converter & clutch plates are slipping. In my case, since mine is well maintain & I want to keep the car for a long time so I've decided to rebuild my tranny w/ new torque converter, clutch plates & all the soft parts rather than swapping w/ a used one as I don't know the condition of it. Since then, car has been shifting silky smooth again.

2013FSport

iTrader: (2)

OP - if the engine flares and the car is not accelerating then you look at the trans.

Lag from engine response / lack of, is more than likely something else. Perhaps the ECU is having issues (bad capacitors look that up) as variables like ignition timing being retarded by bad knock detection input is a possibility.

Think of a flared shift as the tire spinning in the rain. The engine will tach out with no load hitting the rev limiter. If the trans is at fault the fluid will burn quickly. Is it?

Mind you the trans fluid can be bright red/pink and still be burned in smell. Always smell the fluid too. You will know.

Losiracer2

I would say double check the condition of your coolant temp sensor. Unconventional in approach but this one sensor has a lot to do with how the engine runs and operates and directly tells the ECM how to operate the car. It has a pretty big affect on driveability as well. If you've never done this sensor, then its for sure a benefit in mpg as well. First thing I did when I got my LS and I went from 20 to 22mpg in mixed city driving average per tank.