StevieA

'93 LS400
258,000km
No warning lights on except occasional (trac)
Car works fine really except......

I think its a bit tired. When i read some of the top speed threads here of people reaching the 150MPH area and watch some vids of this on youtube I notice - mine doesn't have the strength to get from drive to overdrive at full throttle. It sits forever in the 5,000 rpm range

Although my goal is NOT to travel 150MPH my question is about maybe my car being overall a bit lazy

So I have new Denso plugs, OEM wires, caps, rotors that I haven't yet installed. (I checked the plugs roughly 20,000 km ago and they looked well, decent so I saved all this gear to go with my scheduled timing belt change at 190,000km

To those with experience - would intsalling these items perk it up? - thanks

BobN54

Doubt it. Start with investigating how well the engine is breathing. There is an excellent series of videos on Youtube by Walker exhaust. They explain how to use a vacuum gauge and how to test your catalytic converters for blockages using temperature and back pressure measurements. Make sure your engine is getting up to proper operating temperature. You can also do a compression test to make sure you don't have a weak cylinder. Last, it may be time to send the injectors out for reconditioning.

Kansas

I doubt if the new spark plugs and the other parts are going to help. The spark plug change interval on your car is probably the equivalent of 90,000 miles as on the U.S. gen 1 LS400. I've had three spark plug changes on Lexus LS cars done per the maintenance schedule - at 90K and 180K on the 90 LS I bought new , at 120K miles on the 00 LS I bought at 38,000 miles - and I have never noticed a bit of performance increase after a spark plug change.

258,000 km (160,000 miles) isn't all that much. My 90 LS ran like new with the same amount of power when I sold it 183,500 miles and its new owner recently sold it after driving it to 295,000 miles.

Maybe try driving a similar 93-94 LS400 to see how it compares to yours. The gen 1 LS400 wasn't all that fast in the first place (although pretty good back then) and the larger wheels and tires and increased weight of 93-94 LS400 bogged it down noticeably. The advertised 7.9 second 0-60 accelleration time for the 93-94 LS was pure fastasy and auto magazines of the era routinely commented on how slow the 93-93 LS was compared to the 90-92 LS.

Remember the disclaimer about the supposed 0-60 time for your 93 LS: "Performance capacity figures are for comparison only and were obtained with prototype vehicles by professional drivers using special safetyequipment and procedures. Do not attempt."

Bradster

Seafoam,throttle body cleaning and fuel injection treatment should yield positive results...

mikes7ke

iTrader: (1)

Now if it's not shifting into overdrive, couldn't that be an automatic transmission problem?

You mentioned your TRAC light would come on occasionally. My TRAC light would never come on but I never noticed a difference between TRAC on and off. It felt like an all new car after removing TRAC and ABS though.

StevieA

Well already done several bottles fuel inj cleaner and seafoam.

It;s the lower-case trac light on and not the upper case TRAC. And it's sporadic.

It will shift to overdrive no problem all day. But at full throttle and 120 MPH it doesn't have the guts to get there.....

I do have stock wheels & tires although they are fresh winter tires which would be a bit heavy.

Also, my driver rear wheel has alot of friction. On the hoist it's difficult to turn with two arms. I believe it's friction in the brake pads/caliper. Have to investigate. This could slow it down and may be the cause of the trac light as well.

I have removed all the resonators etc. behind the front two cats & O2 sensors. Straight duals from there back & two mufflers at the end. It has a new air filter but something tells me the hint from BobN54 about breathing is onto something.

I'll post if I find any improvements - thanks for the feedback!

adrenelin5

On the first 2 sentences You wrote today at 7:45 I have a comment that might help you out.

Yesterday morning I bought a bottle of injector cleaner meant to be mixed with 80 liters . I figured I'd be smart and add it to only 30-35. Drove the car for about 75 kilometers over the course of about 5 hours. When on my way home the upper trac light in lower case letters comes on .My first thought was the injector cleaner obviously. Did some reading and came upon a post that states dirty /bad injectors or loss of pressure in the fuel system among other things are possible cause of the codes I'm getting from my trac light which are 43 and 51. I'll be installing a new fuel filter this morning. I'll report back If anything is resolved. Any thoughts?

ocr

iTrader: (2)

You have a N/A motor.. are you shure you didn't have the exhaust made to large to have the proper backpreshure?

adrenelin5

just thought maybe your trac was caused by overuse of injector cleaner which carried a lot of debris forward from your gas tank into the fuel system where a old useless dirty fuel filter may or may not have been to be able to protect the injectors. Or possible that maybe the fuel filter became too plugged itself tripping the trac light.

StevieA

Well the tubing is pretty small. I was just replacing rusty parts. I'm guessing under 2" each side. No more "x" or "Y" in there. Straight dual like a Dodge Viper. Not the best sound...

Thanks. The car did sit for 2 years at 223,000km before I bought it. We replaced the fuel filter (it was stock & a dirty mess) and ran tons of inj cleaner through it. Didn't notice a perf difference before or after but thanks for the tip. However, at least a year passed between the last bottle of injector cleaner and the TRAc light coming on. The trac light appeared right after a brake fluid system flush.

Actually it's the TRAC light that eventually comes on and not the TRAC OFF light. (I originally called it a lower case trac) sorry for any confusion

Anyway I just cleared all my codes and went for a drive. After a mile or so the TRAC light came on (as it does most of the time). Once I was well up to operating temp I found a long straight and floored it. With enough nerve I waited long enough and it shifted to O/D at WOT & reached 130MPH.

I guess it's working good anough. And likley typical for this car. So I'll leave well enough alone.

But another bit of HP (even 100) would make my smile much brighter

Oh ya - then I checked the codes when I got back

ABS light 54 - "Open in TRAC motor relay circuit"
TRAC light 43 - "Malfunction in TRAC control system"

My gut still tells me these are related to the friction issues at my rear wheel because the problem is intermittant. Sometimes I can drive for nearly an hour before the TRAC light comes on. & the traction control system works until the light comes on

Thanks for the help everyone

PureDrifter

iTrader: (10)

engines don't "need" backpressure at all.
what they need is the proper combination of exhaust flow and exhaust velocity.

regardless, too big would hamper low-end torque due to hampered scavenging.

OP needs to do a basic tune-up then start troubleshooting, if it's determined that his car is slower than comparable LS400s.

RA40

iTrader: (6)

As PD mentioned. Good gas is also part of this equation.
The '97 and earlier are not particularly fast. Yes, Toyota's conservative engineering spec in the HP/# ratio has not been good. Getting better now but that doesn't help us old car owners.

adrenelin5

Ditto on the condition of the filter here as well. Just changed it and it was insanely dirty. Anyhow it didn't reset the Trac light but having the neg cable off for 2 hours I'm sure done the trick. I also cleaned the throttle body in the mean time. Still it came back on.

But I am wondering about something I saw when changing the rear brake pads last weekend. There was a wire that was hanging loose. Perhaps it was the wear sensor. It had some black tape loosely on there which I believe fell off before I was finished the job. Never thought much of it. If you had your brakes done and the problem occurred just after perhaps there is a bad connection there that was jostled. Just a thought.

As far as O/D kicking in at 130 MPh. I'm not sure if that would be correct but coincedentally yesterday I opened her up and mine shifted at about 105 MPH. Note though that I have the trans cable(bowden) on the firmer side.

StevieA

Mine has a similar wire hanging. We assumed it was brake pad wear indicator unhooked long ago. They were like that when I got the car long before the light came on.

I have mine set as firm as it will go via the trans cable under the TRAC cover. https://www.clublexus.com/forums/ls4...-kickdown.htmlIt will reach ~ 120MPH before shifting to O/D. This is over 6,000 RPM. Once it finally shifts it gives a nice little surge toward 130 and higher. Notice this one shifts at around 120MPH as well http://youtu.be/WyPPfLn5M7s

Bradster

What i meant by fuel injection treatment is when a shop runs acid (?) through the fuel injectors themselves cleaning them of deposits that have accumulated after running thousands of gallons of fuel through them..After having this treatment done with every fuel injection auto i've had over the years (all previously owned) the difference was apparent the minute i drove away from the shop.