So as some of you may recall I purchased a 93 LS for next to nothing and have been battling with a severe lack of power that has me completely baffled. Would love the input of some veterans.

The Problem:

Car has a severe lack of power like nothing I have ever seen before. Car starts fine, idles well and trans does not slip. However if you enter a highway on ramp it takes - literally no joking - 2 minutes to reach 60 mph.

What has been done:

I replaced all vacuum hoses, identified a broken nipple coming off the intake that was "taped" off. Repaired the intake (JB Weld for the time, will replace) and replaced the hose. Idle did improve to what I can only call almost perfect (quiet, 650rpm).

I had the ECU completely redone by a known professional so I know that is no longer the issue.

New plugs and wires installed. Never really thought this was the problem due to the excellent idle but went ahead and did it. No improvement.

Also checked timing, spot on.

BTW the car is not throwing any codes

The List:

I have a list of things but that can get expensive so I would like some opinions on what to start with (other than cheapest parts first).

1. Shift solenoid?
2. Cats?
3. MAF?
4. Coils?
5. Engine Temp Sensor?
6. O2 Sensors?

Other notes that may or may not help. Transmission shifter is UBER lose. Literally feels like it I could pull it off. Also there is a "thunk" on braking that sounds like a transmission mount.

Thank you for any assistance.

 

I'd put my money on low fuel pressure, plugged exhaust, or bad maf. You could probably unplug the maf and see if it gets any better, as for the exhaust you will need to drop it at the manifolds or pull out the 02 sensors to check for a difference in power, fuel pressure can bea easily checked with a pressure gauge. BTW, the intake will be fine with JB weld, no need to replace.

 

ECT sensor is also possible. Dont want to shot gun this though. Does the 93-94 fuel pump have its own ecu?

 

#5 on your list then the O2 if these are originals. But you would get a code with the O2 sensors.

These two threads:

https://www.clublexus.com/forums/ls4...read-this.html
https://www.clublexus.com/forums/ls4...-in-1-fix.html

 

try unplugging the MAF (AFM) and see if the symptoms change

 

What if something else is inherently wrong with your ECU? Perhaps someone replaced it using a wrong ECU? Or the CPU within the ECU is gone bad (that cannot be fixed by replacing capacitors)?

Shift solenoid will only affect shifting, and while the car will run badly, you would clearly know if it were the shift solenoid (plus it would throw a code).

O2 sensors make very little difference... I replaced mine - they were originals, 25 years old, and except for improved MPG, not much difference in acceleration and power.

What about fuel pump or filter? There is also that problem with the fuel pump relay if I remember correctly...

 

I don't see coils/ignitors on that list.

 

Excellent point.

I had an ignitor go on my nice 96 but then I did not get any fire. I did not know ignitors would effect performance under power.

 

an bad ignitor would have the same symptoms as a bad coil, however ignitors almost never go out on LS400, but coils do occasionally

 

here is a handy test demonstrated on an LS400 just like yours, that will check your ignitors, coils, and the associated wiring to each!

 

I had the same problem when a cheap HKS foam air filter leaked foam onto the MAF screen, perhaps worth a check!

 

once you have tested the coils/igniters (which are likely fine or else it probably would not idle well), then I would do a fuel pressure test using this inexpensive tool, and do a back pressure test using this inexpensive tool. (to verify cats) - you compare readings at precat and post-cat O2 sensor holes.

at that point I would look at the timing belt alignment marks - jumped time could cause the symptoms you have

this will actually not be a hard problem to figure out, as not very many things can cause this

 

That's the same issue I have on my 94 ls400. Lack of power (like 4 cylinders), back fire (like something clogged), and red catalytic converter( unburned fuel).

 

you probably have a dead coil or ignitor, something ignition related. it's likely killing/killed your cat.

 

glowing red catalytic converter is an overheating catalytic converter, this happened to me when my ECU capacitors failed, car ran quite badly as well - and 94 LS400 is about the most common year for failing ECU caps (along with 96)