I have a 2000 rx300 3L, 2 wheel drive. My check engine light came on, and my overdrive went out. I took it to lexus dealer, and they said I needed a new engine, as the knock sensors were detecting piston slap. They wanted $12-13000 to change engine.
I found a local engine mechanic that recommends buying used rx300 engines that come from Japan with 28-29000 miles on them. He can install for $2800. He suggested that I come to see him before he ordered the replacement, which I did this morning. He "listened" with a probe and says that there is only, maybe, a very slight knock, and that he thinks the engine is still good. His advice is to replace the knock sensors. I am throughly confused.....can anyone help?????

Thank you.
Louis

 

I think I would start with resetting the check engine light and running some fuel injector cleaner through it. After that see what it does with some high octane gas. May just be some bad gas or faulty knock sensors.

Any other symptoms?

 

Not really. I run Lucas thru about every 2-3000 miles. With the OD out, my rpm's run at about 4000 at 67 mph. Sometimes the OD works and sometimes not. I go thru the normal shift pattern up to 3rd gear.

 

I think it's ridiculous for the dealer to say that the engine is bad because the knock sensors detected piston slap. Untrue. Knock sensors do not detect piston slap. They are Knock sensors, period. Now the dealer could say that they themselves hear piston slap but saying it's because the knock sensors are sensing it is completely false.

If you're getting an engine light and it points to the knock sensors, I'd say figure out if the car is truly knocking or not. Has it had a tune-up lately? Do you run the proper grade fuel? If you've done that and are running good fuel, then you could just have a bad knock sensor(s). Start with the small things first.

To clarify, do you hear it most when started up first thing after it sitting and getting cold? And does it lessen as it heats up? These are typical signs of piston slap.

 

You need to list other things like, current odo reading. Are you burning oil etc.

There is a lot of diagnosis involved before any conclusion is reached. May be the dealer has already done that.

I would have the CEL reset.

Observe how soon it comes back (if it does).

The problem could very well be due to pre-ignition and can be solved by running with couple of tank fulls of higher octane (or even switch to it).

It can be bad knock sensor(s) too. My knock sensor went out around 150k miles and even with DIY it was one of the costly repairs for my RX. If you ask the dealer the knock sensor replacement will run you close to $1k. So I would not jump to replacing the knock sensors and put money just because it is cheaper than new to me engine.

If you trust another mechanic, get his second opinion.

Salim

 

I'd suggest to reset the CEL. Try another mechanic if you know of one that is honest. I highly doubt it needs the engine replaced, but you haven't told us how many miles the car has so it could be a knock sensor but as salimshah said they aren't cheap. Also, disconnect the battery for about 15-20 mins. and see how long it takes for the CEL to come back.

 

Thank ya'll all for responding and trying to help with my problem. Sorry for the lack of complete info. I have 175,000 miles, and run about 1000 per week. The CEL has been reset, and took about 5 minutes to come back on. I am not burning any oil, but I do have a rear main seal leak (slight), which is another issue.
I do not hear anything at all, and my mechanic could only hear anything by using a probe and earphones, and he said that it could just as easily be routine engine noise because it is so slight. He spoke with 3 other mechanics and they agreed that the thing to do is replace the knock sensors. I can get them at O'reilly for $150 each, and have them installed for about $300. Any ideas?
Thanks so much!

 

Change those knock sensors!
You might want to change the coolant bypass hose while your there, its probably brittle. Also be careful with the little wire harness the sensors plug into. You might want to replace that too.

I have already had this code. Replaced all of the above parts, and my RX ran great again.

 

Can you post the error code? If that says knock sensor and based on other things you posted, i would say replace them. They seem to last this long (expected life). Read the DIY for information or if you want to DIY. You will need harness, gaskets and sensors (bypass pipe is optional, but might as well] .. they add-up.

When it comes to sensors, I am for OEM. The sensors are so buried that I would not take a chance. The originals lasted you 170K, so the quality is good.

People claim it can be done in 4hrs so $300 from a mechanic seems reasonable. Dealer with higher rates will charge around $600 (my estimate, you can check with them).



Salim

 

Ya'll have helped me make up my mind to go ahead and change the knock sensors. I will order them today and have them installed Saturday. I will report back with the results.
Thanks to all!!!

 

Texan!

Salim

 

Southerner!

 

At a checkout counter of a restaurant here, the staff was trying to merge three words.

Salim

 

Salim- I've known a lot of southerners (our DIL is one of them) all the way from Southern Illinois to the Gulf of Mexico and Ya'll is more common than fried chicken for them. The one I never could get used to is "youse". Just doesn't sound right. Not that terribly common though. When our son married our DIL and we 1st met her, we couldn't hardly understand her. No problem now though, I think we've probably both changed.

 

I had the same problem fought it for 3 months. Overdrive drops, told that I have a bas transmission. Bit the bullet when I moved to Florida (after driving from NJ and having to stop and shut off engine to clear up the over drive problem) I had a local indie in Orlando swap out the 2 knock sensors.

Problem solved been running perfect with 150000 miles on the odo for the last 8 months.

Best money I ever spent had him change the plugs and I am averaging 19.8 right now.

Mike