Chilkoot

My '93 Ls400 developed a pretty severe stutter at highway (45-55mph) speeds over the course of about a week. Was fine on the way up or down moving through that zone, but the car felt like it was about to stall out if you tried to hold a partial throttle. There was also a hesitation when laying on the throttle from rolling speed, such as when you're on a 45mph road and the person in front of you turns and opens up a wide stretch of road. I found a few threads with similar issues, but I don't recall seeing any solutions.


Anyways, long story short, I did some digging and not one, but TWO of the four screws that bolt the transmission mount to the transmission had sheared in half. Just got done spending a few hours with a dremel and a flathead screwdriver getting the stumps out. My shoulders hurt. Should have jacked up the car farther.

After the test drive I'm thinking that one of the screws snapped a long time ago, and the second is what caused the vibration, because this car hasn't driven this well for quite a while. Car isn't sluggish from a stop anymore, it's got pep again.


I'm really scratching my head on this one.

deanshark

I highly doubt that the tranny mount was the cause of the hesitation. Vibration, definately yes, but not hesitation. The reason you didn't find an answer in your search about the stutter at 45 is b/c there is no answer. I've been trying to get rid of it on my 93 for a year now to no avail. I have the stutter (skip) at 42 MPH. I just learned to live with it and not drive between 40 and 45.

CitySlaka

I have the same problem with my 92 I wish there was a way cause some times you can't help to go 40 to 45. I aligned my cam and crank after changing my timing belt I noticed it was alittle off and it helped.

Chilkoot

After driving her to and from work, i can most emphatically state that the sheared bolts were indeed the cause of the stutter. My best guess is that the transmission, not being tightly held to the mount, "wobbled" under certain conditions and this presented what felt like a stutter. Under throttle, the torque held the transmission tightly to one side of the mount, while at idle there wasn't enough torque to make it rock, so it was only noticable at a very specific cruising speed.


The hesitation could be perceptual, much like your car feels different after an oil change but the "gains" go away after a few days. Either way, I sure am happy to be driving her again.

I hereby reaffirm my love for this automobile, and my belief that they are the best vehicles ever made!

I replaced the transmission mount about 6 months ago, so I was sure that that wasn't the issue, but I suppose that if your mount was worn enough to let the transmission "wobble" like two missing bolts would, I suppose they could present with the same symptoms.

(If you're getting a stutter at cruising speeds, make sure your transmission mount and all associated bolts/nuts [12 total] are torqued.)


What i'd really like to know is how those two bolts snapped in the first place.

steve2006

Check the throttle potentiometer sensor,the tracks wear out and electrical connection becomes erratic.
The wear is always the most prominent at normal cruising speeds because the TPS spends most of its time in that position,any position above or below that speed is normally OK as the track wear is less.
If you have an old analogue multi meter,the one with a needle, set it to DC volts (0-12VDC) and connect the red to the TPS output with the ignition on but the engine not running and the black lead to the chassis/earth.Slowly open the throttle by hand and watch the needle.
It should move up steadily as the TPS output voltage rises,if the needle starts jumping/flickering at any point this indicates a worn track at that point which should coincide with the throttle position at the cruising speed where you notice the hesitation.
If you can remember the days when radios and TVs had the rotary volume controls they sometimes with age caused the volume to crackle in a certain position,the cause was the same,worn tracks of course with a TPS it causes the engine speed to glitch.

Chilkoot

Gold advice. I'll replace both TPS just to be safe. Much like the ECS after nearly 20 years it's just due.

Is there a list of common wear parts for first gens that should have been replaced by now, even if only as a precautionary measure? Things like the tps, ecs, iacv, hcv, rcb, etc....