90 Knocking And Trac Light

[AzHotLS]

I recently bought a 90 LS400 with 103,000 miles, I've put 4K miles on it and love it! This site has been a great help in getting to know my car, I've learned so much from all of your great posts. I Lexol'ed the seats, WOW! It is a great car and fun to drive but I have a couple of minor issues I tried to take care of that I need help with.

I found a shop that specializes in Toyota/Lexus cars. I spent $844 having various things done (lube/oil, tranny flush, coolant flush, rear diff fluid, drive belt, throttle body decarb, and throttle position sensor) to get it up to snuff, but 2 things still linger.

1) The engine was knocking, but only when fully warm. I had the throttle body decarbed ($141) but it still knocks. I'd say it's 70% better but not gone altogether. What is the next step? Aside from the embarrassment factor, I'm concerned it's doing damage. I've seen other posts indicate it could be the valves.

2) The TRAC light was coming on ocassionally but usually only when ECT/PWR was on. The Throttle Position Sensor was replaced ($246). The light is still coming on, more frequently now, even with ECT/PWR off. Can the sensor be adjusted or is it bad as well. What next? I should add that one wheel is bent, the shop where I get my tires was able to balance it but I do notice a vibration when driving, could this cause anything related to the traction control system, I had them rotated when they were doing all this work but don't know if it is on the front or back (before or after). I haven't had time to get the bent wheel swapped with the spare's but plan to do so very soon.

While I'm at it, 3) it was recommended to replace the tension rod bushing ($251), rear trailing arm bushing ($383)and oil pan gasket ($262). I told them to hold off on these. Will I need to replace the bushings before I put new tires on the car? I plan to do this in the next few months I don't see any oil in the driveway so I also said no to the gasket.

[VBdenny]

Well, they all knock a little, I don't think it hurts anything. Just a little pinging actaully. You did change your gas station I hope. This front bushing, yeah, they go bad. Makes a big difference. I don't know about the rear trailing arm. Mine (luckily) does not have traction control or air suspension..

The oil pan gasket sounds like pure BS.

I recently bought a 90 LS400 with 103,000 miles, I've put 4K miles on it and love it! This site has been a great help in getting to know my car, I've learned so much from all of your great posts. I Lexol'ed the seats, WOW! It is a great car and fun to drive but I have a couple of minor issues I tried to take care of that I need help with.

I found a shop that specializes in Toyota/Lexus cars. I spent $844 having various things done (lube/oil, tranny flush, coolant flush, rear diff fluid, drive belt, throttle body decarb, and throttle position sensor) to get it up to snuff, but 2 things still linger.

1) The engine was knocking, but only when fully warm. I had the throttle body decarbed ($141) but it still knocks. I'd say it's 70% better but not gone altogether. What is the next step? Aside from the embarrassment factor, I'm concerned it's doing damage. I've seen other posts indicate it could be the valves.

2) The TRAC light was coming on ocassionally but usually only when ECT/PWR was on. The Throttle Position Sensor was replaced ($246). The light is still coming on, more frequently now, even with ECT/PWR off. Can the sensor be adjusted or is it bad as well. What next? I should add that one wheel is bent, the shop where I get my tires was able to balance it but I do notice a vibration when driving, could this cause anything related to the traction control system, I had them rotated when they were doing all this work but don't know if it is on the front or back (before or after). I haven't had time to get the bent wheel swapped with the spare's but plan to do so very soon.

While I'm at it, 3) it was recommended to replace the tension rod bushing ($251), rear trailing arm bushing ($383)and oil pan gasket ($262). I told them to hold off on these. Will I need to replace the bushings before I put new tires on the car? I plan to do this in the next few months I don't see any oil in the driveway so I also said no to the gasket.

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[90LS400Lexus]

I agree with VB- I doubt the oil pan gasket needs replaced. My 90 LS had 235K when I sold it and there were no drips. There was some minor "crud" on the pan, but nothing major.

About the "knocking" sound- it is a low toned knock, or a lighter sound "tick". My car had the ticking noise and it seems to be common. I drove my car for several thousand miles like that and it did not get any worse. I cannot say for sure, because I have not heard your engine. Just keep listening to it good and make sure it does not get worse.

[silvermate]

as you can see if you pay someone to do the repairs it adds up QUICK.....i promise you can do most of the things you mentioned, you paid for,,, especailly the TB cleaning, but you gotta do what you gotta do, and i understand that :)

about the oil pan gasket leak.......i changed my oil last weekend....and i noticed there is some sludge and a little "wetness around the oil pan gasket......i know it is seeping a little (very small leak, no dripping) b/c everytime i change my oil i always thoroghly clean the surrounding area, as to check for things like that.......its very very minor, but i'm all about prevention

anyway, i'm gonna change the gasket out in a little while, as not to waste my Mobil 1 i just put in there.......its a very easy job, and i'll make a tutorial when I "getter done"

good luck

[AzHotLS]

I took it to the shop this morning.

They said a little pinging normal, and based on the replies I got, I can live with that. Yes, I would have liked to have done the throttle decarb myself, but time is money as they say.

The TRAC light is a carry over from before they replaced the sensor. The process to reset the code is different on the 90-91 400s compared to 92-94s. I didn't catch all of it but you have to short a couple jumpers and press the brake pedal 8 times. You can't be in the club unless you know the secret handshake.

I'm taking the car to my tire shop now to see about the vibration.

[AzHotLS]

At the tire shop, they found the bent wheel. It was on the front left, swapped it with the spare's which fortunately was a left wheel also, I'm happy to report that the vibration is gone. :D Now I can see how smooth it's supposed to drive.

However, the TRAC light came on again! What's up with that? I barely drove 4 miles. Did the secret handshake not work to clear out the computer or is there something else wrong or needing adjustment?

[ec437]

about your knocking, you are using premium gas, right?

[spiller91ls]

you didn't say if the Knocking is happening when your car is idling or when you are actually going down the road. If it is happening while idling, then it's the valve lifters, and it's something that we lexus owners live with. If it's doing it when you are going down the road, then start running higher octane fuel.

If they can do a oil pan gasket for that amount, then let them do it, i've looked at doing mine and i'm pretty sure that the only way to do it would be to remove the engine from the car.

[VMF]

this knocking is prolly valves, its ok to have it like this, but if you really want to fix it, valve alignment job will cost you around 400$