Hi everybody,

As I know that Lexus engines are the best and are heavy duty. Wherever I read, there were very few complains about Lexus engines. However, for the last 2 weeks I have been hearing a strange noise from the engine. The noise comes when I press the peddle slowly on slow speed and high gears.
Example: I am driving at 40 M/H the car is on last gear(4th I thing) then I press slowly on the paddle, then I hear a rattling noise from the engine, then when the RPM goes high or the gear **** to lower gears the noise vanish

The noise is like the noise that is coming when you drive a manual gear car and by accident you shift the gear from 2nd to 5th and low speed and then you press the paddle. It is like the engine valves are having a party.

I took the car to the dealer and he said that it is a fuel issue. He claims that either more fuel is pushed to the engine or less fuel is pushed to the engine. He recommends changing the injectors.

My car is SC430 2004 with only 33000 miles and I did a major service on 17000 and another two minor services on 23000 and 28000 miles.

The timing belt is replaced and it was adjusted perfectly.
A friend who has a LS400 says that this happens when there is a shortage on Oil or when the Oil quality is gone. I changed the Oil and add more Oil but the noise was still there but only it reduced the noise.

Please help me

 

From your description my bet is that your engine is knocking otherwise known as pre-ignition. This can be a fuel quality i.e. octane issue. Have you gone through one or more tanks of gas since this noise began? Are you using premium? Your engine has anti-knock sensors that listen for knocking and adjust the engine timing to avoid knock even while running regular. I believe that there is one knock sensor per side of the engine. I suppose that one could be bad and therefore not doing its job. Did the dealer check for codes with their diagnostic computer? If you're in warranty I'd let the dealer replace anything that they like while chasing the problem but if it's your money then I'd have them perform more diagnostics rather than rush to judgement and start throwing parts at it. By the way, fuel injectors can be cleaned, and should be, before they are just replaced.

 

Thank you Bon for your reply, this really give me hope

Do you mean by Pre-ignition = detonation?!! This is what the dealer mechanical said that my car has a detonation!!
After the noise came I have gone through 3 tanks and changed the Oil & filter also. I am using an 98% unleaded fuel and here is its specifications http://www.adnoc-dist.co.ae/portal/product/green.asp.
I don’t know about the anti-knock sensors but If you mean the oxygen sensors then they are fine and no problem reported from it. If the anti-knock sensor is something deferent then please tell me where I can find it and how to test it.
The dealer check and there are no error codes coming at all !!!! I only noticed few things that appeared only after this strange noise start coming:-
1- Performance is getting lower than before since the knocking noise.
2- Whenever I fill gas and the engine is running, the RPM drops very low and the whole car start shaking for few minutes then everything goes back to normal. That was not the case before the strange noise.
3- Fuel consumptions is increased a little bit.

Unfortunately, am out of warranty as my car is imported from US, so am paying every thing from my pocket. So I tried cleaning the injectors by using Toyota injectors cleaner two times. Once I left the tank on ¼ then I drop 1 can of the cleaner into the tank and fill it up and drove the car, no improvement. Second time the tank was ¾ and I drop 1 can and filled the tank and drove. Same results, no improvement!!!

I really appreciate your help Bon. Anymore recommendations for me

 

Any leaks? Any smell of gas? You mentioned performance has been worse...how about gas mileage? When you stomp on the gas, is there hesitation or mis-firing (spark plug related)?

Did this just happen after you did the timing belt? Who did the timing belt? What else did they do when they did it?

I'm thinking injector related when I read it, but it would be helpful for us to have you answer these questions.

So, do you use Premium Gas? At least 91/92 octane? Have you tried other brands?

In my opinion you shouldn't be having this problem. Strange for your year/mileage.

 

Yes, pre-ignition is detonation. The knock sensors are not the same as oxygen sensors. If the knock sensors are bad you should be getting a check engine code but you didn't mention that you are. If the knock sensors are doing their job you would expect less power/performance as long as the knocking is occurring so I'm not surprised that you mentioned reduced engine performance.

Are you getting any check engine codes?

You mentioned that you had the timing belt replaced but you have only 33,000 miles. Why was the timing belt replaced so early? Did a Lexus dealer do the work? The timing belt cannot be off by even one tooth or you can have this kind of problem. The only correction is to go back in and reinstall the belt to correct the problem.

Was the belt tensioner replaced? A broken/loose tensioner can rattle around making noises.

Has anyone checked the engine timing?

Fuel injector cleaners didn't help, new fuel hasn't helped, but I wouldn't start throwing parts at it as that can get expensive pretty quickly and be frustrating. On the other hand, be careful, don't let the engine knock too much as this can lead to major mechanical problems.

I can't help but be suspicious about the timing belt.

 

Hi scdroptop,

No leaks at all and also no smell of gas. Gas mileage is dropped from usually 23-25 MPG to 18-20 MPG!!!!!
There is no hesitation or mis-firing at all and the Plugs are recently replaced with iridium new ones in Lexus dealer.
No it did not happened after changing the time belt immediately. It happened long time after that. The Lexus dealer did the time belt changing and all the parts where original. They have changed two pulleys, plugs, all filters, belt, all liquids, fix the break, changed the AMS…….many things (4 A4 pages and around 3500$ bill)
I am using unleaded fuel that is 98% all details of this fuel are in this link
No I did not try any other brand of fuel, should I try?!!!!

Thanks you and waiting for your comments.

 

Hello ,

No am not getting any check engine lights at all!!!! I changed the time and did a major service after buying my SC because it was imported from US without any service history!! So I thought the mileage could be wrong!!!! Also the local Lexus dealer advised to do a major service and change the timing belt with many other things after a major inspection done in the dealer workshop that took 5 days to check and then 12 days to fix and repair!!!!!!!!!!!!
I checked the time belt in another dealer for Toyota and he confirmed that it was correct, then I checked it also in another Lexus dealer and also confirmed that the time belt setting are 100% ok.

Everything related to the time belt was replaced with new original parts.

Thanks for your concern and help

 

Do you have another Lexus dealer in your area you can take it to for a second opinion? If not how about Toyota?

I would certainly try another gas. In Texas (not sure where you are at??) you can get 93 octane and that is what I use for all my luxury cars. I looked at your link for the gas and couldn't really decipher at first glance what the octane was, but I'm not a gas expert by any means.

Why was the timing belt replaced so early?? Were you having trouble with the car? And plugs too?

 

+1 on trying other brands of fuel, I use Shell premium, never a problem. Could this be a fuel pump issue ?? I'm thinking injector or fuel pump. Good Luck

 

From what you have said the Lexus dealers have been ensuring that your maintenance is up to date. Are they aware of your pre-ignition complaint? Have they test driven the car and do they agree that you are experiencing pre-ignition? Have they examined the data from the engine ECU? The data should show them if the engine is experiencing a lean run condition as well as data about operating parameters for fuel delivery, fuel pressure and ignition timing. Heck, the ECU even remembers if a spark plug didn't fire and knows which one. If the knock sensors are indicating knocks this is also recorded. The ECU data should show that it has been compensating for the engine knock and should show how far it has adjusted to avoid it by adjusting ignition timing. If the ECU doesn't show this then it's likely not engine knock and you should look elsewhere to find the noise.

If the dealer hasn't specifically examined your car for this complaint then I would leave it with them rather than drive the car because, as I said before, pre-ignition can easily destroy your engine very quickly and suddenly as it is very, very hard on your can be very damaging on engine pistons, rings, rods, gaskets, bearings, and even the cylinder heads. It can destroy your engine in seconds.

 

From your link Turboo, it appears that the gas you are using is 97 octane. Have you always used that high of octane? (That is getting up there with avgas.) If you changed to this from regular fuel, you might consider changing back to a gasoline made for your typical automobile today (87 to 91 octane).

 

Turboo is in Abu Dhabi and RON97 gas is unleaded+ gas there. RON95 is more like regular and RON99 is equivalent to super premium. The higher RON numbers resist knocking more than lower RON fuels.

 

Among all suspicious faults I personally think it is a fuel pump issue also.

Let’s see what it will end up to.


Thanks

 

Actually, I did not have this issue when I took the car for major service. Also did not have it even after many months of the major service. When I heard the noise I immediately took it to the dealer and he said it is an injector’s issue!! But I refused to change the injectors as it was expensive and I felt that the dealer should do further inspection before judging on the injectors and ripping me around 1500$!!!!

Bon, I am sure that you are definitely right about the damage that it might cause to the engine and therefore, I will stop driving this car till this problem is solved.

I will take it defiantly to the dealer and for sure I will ask him to read the ECU and do as much analysis as they want.

Thank you very much for the support

 

Bone, you are really knowledgeable and a great support. Thanks for clarifying this issue. Usually when I say I live in AD, people will be surprised and most of the time won’t know where AD is

Thank you Harold57 also for your comments