dwayneamir

I recently got a 92 SC400 with 198300 miles on her. Here's the symptoms I need assistance diagnosing, and if possible, suggested DIY repairs.

1. When I shift from reverse to drive, the car surges forward, the entire body of the car surges

2. If I press the break firmly and shift to drive (D), I feel the surge less

3. From a cold start, shifting straight to drive (D) from Park (P), the car does not surge as much

4. When the car is warm, for instance, if I reverse, then change to drive (D), the surge is more violent.

I got the car late July and so far, I've changed the motor and transmission mounts. When I first got the car, it would surge whether I shift into Park (P), or Drive (D). After I change the mounts, the car does not surge when I shift to Reverse. It's silky smooth. I'm guessing the rear transmission mount had something to do with that.

Thanks for your help, suggestions and advice.

dwayneamir

Any help would be appreciated.

MooJohn

Does the car idle at a normal 700-800 rpm?

dwayneamir

Yes, it does. When it idles, I barely know the car is on.

ChrisH

Might be failing tps. Any CEL?

dwayneamir

No, there's no CEL. I could check on the TPS this weekend.

MooJohn

There are a couple of thorough TPS how-to's out there. Having an old computer power supply to chop a connector off of makes it even easier. Then it's just a matter of checking continuity and/or resistances between some of the pins.

scoobySC3

iTrader: (1)

I know very little about automatic transmissions, but I would think that it would be a torque converter or clutch plate issue. As it just sounds like they are locking up a bit more than they should. When was the last time the trans fluid was changed?'

Thanks,
Rick

TweakTech

iTrader: (2)

the body jerking sounds like bad mounts/bushings. and by surging, do you mean the RPMs vary?

dwayneamir

Hey Rick thanks for your input. According to the car's service records, the vehicle was "DRAIN TRANSMISSION FLUID. INSPECT FOR LEAKS. TRANS OPERATING CONDITION" in 10/1998 and 3/1998. Then in 2/2003 the car had "MINOR AUTOMATIC TRANS SERVICE." The three services were done by Lexus dealers. After 2003, there are no records. So I would estimate last transmission service was 9 years ago.

dwayneamir

I changed out the engine mounts: 2 front and 1 rear a month ago, and did notice that the car is quieter and much smoother shifting into reverse and while idling. I was also told that my the front LCAs needs changing.

No not RPMs. When I shift into drive (D), the car kind of jumps/pushes/surges forward. Imagine that you're parked too close to a car in front of you, and shift into drive, while holding the break too lightly. As you shift into drive, the car jumps forward without you pressing the gas not sure I'm explaining it right, but it's something like that.

SC400slide

iTrader: (11)

I would have said Tranny mounts but i replaced tranny mounts on my 92 SC4 and it very intermittently surges when it changes into park, drive, reverse, and RPM's move up in certain shifts. Like in neutral it has a low idle, about 500 RPM's. in park, it run's at 1200 RPM's or so. Is that what you mean by RPM's vary?? Cause I would like to fix that to.