93 LS400 starts fine, engine stalls when put into gear

[LexusInCMH]

I own a 1993 LS400 and have a weird problem. 

 

Note: I do not and cannot do my own repair work. 

 

The problem:  the engine starts perfectly. The engine will accelerate in RPM - no problem. As soon as the car is shifted into any gear, the engine stalls immediately. The engine will start immediately and run until it is shifted into any gear. (It is an auto transmission, so into gear means D or R).

 

The car was towed to a Lexus dealer a few months ago. I really thought this would be a quick fix. However, the dealer is totally stymied. They really don't know what is causing the problem and haven't a clue what to due. It is only an extra back up car for me, so it just sits at the shop. 

 

Anyone have any ideas or could recommend a good Lexus knowledgable shop/mechanic in Columbus, OH??

[sha4000]

Is your check engine light on? If so, what were the codes that the dealer pulled? Can you give it gas while in park?

[LexusInCMH]

No. Check engine light. 

Yes. Engine runs fine in park and revs up fine. 

 

 

[Exhaustgases]

One thing that can cause it is a wire or connection that is only touching and making contact when the engine is not moving, putting in gear causes engine to move, and then connection is lost. Also when the transmission is shifted to a gear position the selector switch tells the Ecu that its been shifted to a gear. There could be something that shorts out when being shifted, or something in the ecu that instead of idling up the engine it cuts if off. I think trying another known good ecu would be my first thing to try. Then checking out the shift selector switch, then looking for and important wire in the harness or even a loose connector. That is easy to do you can just try moving wires a bit when the engine is running and see if it shuts off or does something funny when doing that.

Another test would be to jack up the rear wheels so there is very little torque moving the engine and see if that stops the problem.

[jamesm182]

Sounds to me like the transmission could have some sort of internal failure.

[Exhaustgases]

jamesm182,  thank you I wasn't even thinking transmission loading it.  If the torque converter clutch was stuck on for some reason as soon as you put it in gear it would load it down and stop it. Good thought you had.  It would kind of jerk after the shift into gear before stopping the engine. I wish people would report back, and not just post a problem and never show up again.

[jamesm182]

On 3/11/2016 at 6:11 PM, Exhaustgases said:

jamesm182,  thank you I wasn't even thinking transmission loading it.  If the torque converter clutch was stuck on for some reason as soon as you put it in gear it would load it down and stop it. Good thought you had.  It would kind of jerk after the shift into gear before stopping the engine. I wish people would report back, and not just post a problem and never show up again.

Definitely, I always like to hear if a problem has been sorted and what it turned out to be.

[landar]

James, that the Lexus dealer is stumped just blew me away. I got a good chuckle out of it. Obviously, you can forget that dealer.

Since your car is a 93, have you checked the trunk wire harness for chafing? Its a common issue with that generation that causes weird things to happen.

And, if it were me, I would try putting it into gear while 'feathering' the gas pedal and see if it will go. Obviously you need to be careful doing this with your left foot firmly planted on the brake while you give it gas with the right foot. If the engine stays running when you put it in gear then you may have an air idle up issue. But if it stops dead even with more gas, then it may be the torque converter locked up or another transmission issue.

[sha4000]

I'm not suprised that the dealer is stumped. Those new techs have probably never had to diagnose the older cars and especially when they don't have the check engine light to guide them.

[billydpowell]

sure sounds like a locked up converter to me, rev it up and throw it in gear (empty street)  and hold on, OR, remove the TC/FW bolts and put in gear (on other autos I was able to push the TC back for clearance)  never had to do a Lexus.. 

 Randall has a photo of a FW with bolt showing in his files 

[billydpowell]

this might help

[gymguy]

Had a 93 with same problem. After much work I discovered that the ECM (computer) had bad capacitors that eventually start failing. There's a topic somewhere on this forum that details the fix which involves repaired computer that will work but you have to either find one in a junk yard that has already been fixed or find a company that does the repair. I was lucky to find a wrecked 94 that had been repaired and had a warranty on it. I am an electrical engineer so I can repair the old computer with new caps (cost about $10 for the parts). That's why I'm here to find the info on parts location so I can fix it and use it as a spare. The repair companies that repair these things charge about $900 for one with a warranty.