Hello All,

I have a 94 Lexus LS400 which I have recently purchased.

The previous owner did not service the vehicle.

Here is the issue, when you put the car in gear on drive and push on the gas more than, lets say a 1/3 of the pedal it starts jerking, the CEL comes on. If you keep pressing on the gas pedal loss of power, the car decelerates. If you quickly move your foot off the gas pedal and back on it keeps pulling. Sometimes it follows by that same “hiccup” and is solved by the quick foot off and on.

Unfortunately, I do not own an OBD1 diagnostic, nor know anyone who does. Doing a bit of research revealed that the obd1 system is primitive anyways and won’t tell me much like obd2 will

Here is what service I have done so far,

Oilchange, spark plug + wire set, extensive cleaning of the throttle body inside.

Drained the old trans fluid 2 times and filled it up with new fluid + Lucas.

Tightened the throttle cable going to the trans.

After that it has improved, there is much more torque, and I can push the pedal ½ way before the jerking/hiccup happens. Highway tested upon ½ gas pedal acceleration it just keeps accelerating.

If I shift down to 1 or 2 and ½ gas pedal the RPMS go up and so does the torque with no hiccups.

It seems to ONLY happened upon stomping/flooring down on the pedal.

When in park, and I push on the gas pedal or floor it the engine has great response, and goes up to 5-6k rpms with no issue.

So, here is my question after all of this typing!

Has anyone dealt with similar issues on the ls400 sc400? What was your solution to fix such problem?

In your opinion is it the torque converter, or a faulty solenoid? Or is this due to a very worn timing belt? Have I overlooked anything?

Your opinions/answers would be much appreciated. If you answer with the part that you think is bad, please include why you think so.

Cheers!

Vette33

 

Sounds the same as one of my problems on my 93. Mine ended up being a bad coil. Drivers side coil gets alot hotter being in the location it is. It's one of the common problems but you should pull the codes first. The OBD1 doesn't tell you exactly what it is but it points you in the right direction.
Here's how to get the codes; http://www.lexls.com/tutorials/intro/codereading.html
Here is some tests I found for a hesitation problem, (some good reading material) https://www.clublexus.com/forums/per...on-issues.html

 

Every found out what was wrong? Im Having the same exact issue. I can do 80mph on the freeway if i baby it 1/3 of the pedal only. But as soon as i floor it the car starts to jerk and decelerate.. Need help !!!

 

Don't know if the original poster figured his out but a new coil seemed to fix my 93. But now I am having the same exact issue now on my 94. This time the problem is 100% a bad ECU. I know this cuz I changed it with another ECU and the problem instantly went away. I've since had another problem with that ECU so I put in the one with these problems and everything came back. Soon I'll be sending my other ECU out to get rebuilt.
https://www.clublexus.com/forums/ls-...capacitor.html
The way I drive it now is starting off with the shifter in 2, easy on the gas. At about 2500 - 3000 RPM shift to D and then OD. Ya just gotta get used to it. Hope it lasts til I get the ECU fixed.

 

Can I just swap my ecu with any other 93 ls400 ecu or does it have to be programmed for my car?

 

93-94 are interchangeable for drivability. Only difference is if you have traction control or not, I think. But it will drive. I had my 93 ECU in my 94 for a little while.