929rider

iTrader: (1)

my buddy just got a 93 ls400 and it has the same slight hesitation.
also staying tuned.

perks2

So, did anybody get to the bottom? What is causing the hesitation? My 1993 LS400 is doing it terrible.
Perks2

94ncls400

iTrader: (1)

For me the ect sensor and fuel filter changes did wonders. I still have some ironing out to do, but those two were the cheapest and easiest to start with. Just make sure you set time aside to do the fuel filter lol.

baffledLS

I hate to tell you this, someone told you the solution to your problem already. IT NEEDS AN ECM.

This is the second Ls400 that I've had almost the very same issues with and in the end, it needed an ecm. YOU CAN THROW ALL THE COILS, PLUGS, WIRES, CAPS, ROTORS, EGR VALVES, INJECTORS, FUEL PUMPS, ETC AT THIS NEVER ENDING MONEY PIT AND IT'LL BE THE ECM I N THE END. In actuality the Lexus Ls 400 is a well put together vehicle, but for it to have a computer fail that doesn't even show failure codes or even a check engine is unbelievable.

Then to find out that the 93-94's that this is a very common problem makes matters worse. You're wasting your time chasing "phantom" issues when the ecm is junk to begin with?!

In my opinion for the age of this car, to be sinking money into it when a problem like this is pointless. Heaven forbid you now take to a shop and you haven't been maintaining your car per se' and have to go through all the common sense items first just to eliminate them from the equation. Just to get to the ecm and you're paying shop labor rates?

You have to truly love this car to continue with this sort of insanity.

In the end it's just like a bad marriage, you have to know when you've had enough.

crcuevas

I have the same problem. It idle great!!! No problem starting but when hitting the gas pedal it wants to die at 1400rpm. I did \change the knock sensors and the wires (rats chewed the wires) and When I put it back together I had this problem. I did take the ECM out and visually looked at it but didn't any bad caps.

Maybe I should just replace the ECM anyway?

RA010623

iTrader: (1)

my seem to have hesitation when i'm coming to a stop feels like transmission or diff is locking up.

jerryparks

iTrader: (1)

I had some hesitation in my '92 LS400. Changed places where I purchased gas and made sure it was 93 oct. I also added a bottle of injector cleaner. So, far, this seems to have fixed my problem. I'll check back in later, if it does not. Earlier, I put in new plugs and changed the air filter and cleaned the gunk off the TB. I have had a marked improvement in performance and
so, far, no hesitation.

94ncls400

iTrader: (1)

To the OP, I changed both ignition coils in conjunction with my previous post to you and my problems are gone. I highly recommend you do the same if your mileage is high, otherwise proceed with the other ideas both soft spoken and loud .

cpestinger

this has been so helpful. Thank you all.
Before I read any of this, I removed my air filter and the problem went away in my garage. *not driving
I started the LS in garage with air filter in and floored it and it had the issues described herein. Same test with the air filter REMOVED and there was no problem. (hood up in all tests with all air flow parts removed -snorkels/vectors/cold air/whatever)
I replaced the AF which didn't resolve issue. BOO! So I then replaced the FUEL filter as I just bought the car with 250K and had no idea what was going on. That didn't resolve the issue but needed to be done anyway.
BUT AGAIN with the air filter out of the car the problem goes away. I DO NOT SUGGEST DRIVING A CAR WITHOUT AN AIR FILTER, but for testing it was interesting.

I don't want a junkyard ECM. So I am asking for suggestions on where to get REMAN or NEW ones. ALSO need to ask advice on how to get exact matching units as I saw on other posts that junkyard units may not match up to my exact car.
Thank you everyone. And to those of you who bagg on others for too long of posts... some of us VERY MUCH APPRECIATE information and details.

cheers

crcuevas

Ok, I send in my ECM/ECU for repair not knowing if it needed it or not. Got it back yesterday and still the same problem. This VERY FRUSTRATING. I can't figure it out. Any suggestions? What's next? I have no code and it idles perfect but can't go beyond 1200 rpm.

kayuwong

I had a similar problem like most 93-94 LS owner, rough idle at start-up and stall immediately, running rich on fuel, glowing red on exhaust manifold. Your AC compressor will not engage if your ECU is bad. Took out my ECU and found out one capacitor is blown. Roll my dice and picked up an used one at local junk yard. Plug in and everything is perfect including AC blowing cold air. Don't be lazy, take out your ECU and have a visual check-up. If you see brown goo coming out from the capacitor, chances are they are about to go out. One of mine is blown and I found another one has some brown goo at the contact. Good luck to all LS owner with this proble.

blunden

crcuevas, is one of your cats glowing red?

crcuevas

Don't know. How do I check? Lift the car up and run the car for a while and look at them? And if one of them are red what does that mean?

BTW, this all started after I replace both of the knock sensors and put everything back together. Can the knock sensor cause this? I have no engine codes at all.

Thanks

blunden

Just look under the driver's side door. If the cat is hot, you'll know it right away.

My problem happened after I changed the spark plug wires. The car was running on only 4 cylinders. (It is the unburnt gas that causes the cat to glow red.) The problem, in my case, was the short wire running from the distributor to the ignition coil on the driver's side. I used non-OEM wires, which are poorly insulated. The wire was touching the engine block, and shorting out. The OEM wires have an extra layer of insulation to prevent this.

crcuevas

It will not go beyond 1200 rpm. I did replace the knock sensors and that involved in removing the intake manifold. Replace the gaskets and put everything back to together and thats when the problem started. Also had the ECU repaired and same problem. I'm back taking it a part again to see if i missed anything. Now I did noticed that the air intake gaskets had oil residue? is that normal? Should i replace the gaskets again? The motor will not pass 1200 rpms (sounds like it wants to die). But it idles great!!!! and starts with no problems.