CMDSlick

Hi guys,

I just purchased my first LS a few weeks ago, and I'm noticing some performance issues. It is a 93 LS400 with 34K miles. The car was obviously garaged for some of it's life as it's a 21 year old car at this point. As I understand, the original owner didn't drive much, passed away, and the kids traded the car as they didn't want it. (Their loss my gain)

The car was looked over at both Lexus and Dave Smith Dealership which is local to me and they are one of the largest in the nation. New tires, new air filter, new oil (which I think is dino, so I will be changing that shortly to mobil 1 and a larger filter... thank you LSCowboy).

However I'm noticing a hesitation or sluggishness after the car has warmed up a bit. When I first get in the car and drive, I get quite a bit of pep and then that slowly goes away to where I really have to romp on the gas pedal to see any real pep. Now don't get me wrong, it can get up and go, but I can tell something isn't quite right. Also currently only getting 15mpg around town and this is with a VERY light foot (haven't had the chance to test much on highway yet).

I have changed the engine coolant temperature sensor, which didn't seem to help much. I also dumped a can of Seafoam in this last full gas tank, which I'm about 1/3 through and about the same mileage as last tank. I'm thinking the problem could be the fuel filter or O2 sensors and have ordered both which should be here tomorrow and will be replacing them on Saturday. I might also change out the oil even though I have used if a fraction of the time it can go for.

I have a question on the O2 sensor, wondering if 21 years and only 34K miles would still cause them to break down. Is time a factor as well as mileage or just mileage?

Also if anyone else has some ideas, please let me know... I'm all ears. Thanks.

Legender

I'm assuming you don't have a CEL light on and that the light does work when you turn the key on... which leads to possible capacitor problems in the ECU... I have a 93 with 130k on it and the EXU was replaced a while back, but still know the capacitors need to be replaced... I'd look at the ECU thread.
Sounds like it gets worse as it warms up... making the capacitors not function properly.. just my humble 2 cents.

CMDSlick

Hey Legender, thanks for the info... I don't have a CEL light on and I'm not seeing it come up with I turn the key on... What does that mean, and what action should I take?

I did read the thread on replacing the capacitors, and I'm certain a friend and I can handle that if that is what is causing these issues.

RugbyDad

Gotta replace the bulb in the cluster. I believe the indicator bulbs are all #74. While you're in there might as well do some cluster maintenance/cleaning.. To avoid the needle sticking issue and just to replace all the bulbs honestly..

Might as well do all that while you've got the instrument cluster disassembled

Legender

There is also a way...somewhere on this site... to check for codes on the 93... you have a diagnostic port in the engine bay... I think it's on the driver side, top. but won't support OBDII hook ups but you can short some pins and figure things out if I remember.

You should have a CEL light on when the key is turned on... as mentioned, probably a bad bulb...and you may have some codes that could help you.

Love the low miles, but hate that it came with a few problems.

CMDSlick

Please forgive my ignorance... when Legender mentioned the CEL light, I was looking for a light that said CEL on it until I realized he meant the Check Engine Light.

The entire instrument panel was replaced at the dealership before I purchased it, so I believe I'm set as far as the lighting goes, and yes the CEL does come on when I turn the key on and then goes off after the car has been started.

I did read up on how to wire up the car for the ECU readout on the dash lights with the codes from lexls.com and will definitely try that on Saturday when I change the other items. Knowing this, any other thoughts guys? Super appreciate your help.

PureDrifter

iTrader: (10)

test the ignition coil, ive seen issues when they start crapping out they die when warmed up.

CMDSlick

Thanks PureDrifter, do you think an ignition coil would go bad with time even though it has low miles? Or is it more likely to go out after long use?

CMDSlick

Yesterday, I installed the new fuel filter and the two main oxygen sensors in my LS (the two sub oxygen sensors were a wrong fit), but the sluggish performance after the car warmed up still continued. I may still replace the sub-oxygen sensors, but first...

On to changing out the capacitors on the ECU. After your suggestion Legender, I think you may be right here. I have a friend that worked on circuit boards for a living a while back and he offered his help. Capacitors are all ordered, and I should be doing this in about 10 days.

Boxcuta

I had a similar issue shortly after I purchased mine. I replaced both ignition coils and it came back alive. 😼

PureDrifter

iTrader: (10)

replace.
the.
coils.

CMDSlick

Ok. I will head to the parts store and grab them. Sounds like the drivers side one is a bit of a PITA. Any instructions out there with pics?

Thanks.

CMDSlick

Got the new ignition coils today and installed.

So far the power seems good on the low end where it wasn't before. But it could be in my head. I won't know until I have driven it a bit and it gets really warm, and I didn't have any time this evening.

CMDSlick

PureDrifter and BoxCutter... You guys are awesome.

As far as I can tell the ignition coils did the trick. Great power all the way through and even after the engine warms up. I am testing the mpg now and hopefully will see the increase I'm expecting. At this point I'm about 95% sure that the coils were the culprit, but the days have been cooler lately and I could be imagining things.

I'll post more once I know. I'm also going to replace the capacitors on my ECU as they will most likely go out at some point on my vehicle and I plan on driving this for a long time.

OKSTANCE

glad that ended up being the fix! when my starts running rough after getting warmed up my a/c wont blow cold and i usually have to shift through the gears manually so figure thats gotta be my ecu..hopefully the injectors are all you need tho