topgun129

Hi,

I have a 99 Lexus ES300. Lately, I've been noticing when accelerating (*especially* in an incline/uphill) there is a weird rattling noise coming from the engine (kinda sounds like a diesel engine). I can't feel any vibration of any sort but the rattling concerns me when I'm on the accelerator. Is this a common issue?

If I take my foot off the accelerator and let the car coast the noise goes away.

Has anybody here experienced something like this before?

Thanks!

Bedore

It sounds like your engine is pinging (spark knock, etc). What fuel do you use? Try running some premium fuel and see if the noise goes away. Is your check engine light currently on? Report back.

Ariyanna

Make sure to sure use 91 octane if ur using 87 it will cause pinging/knocking under acceleration.

Bedore

This is incorrect. The motor is equipped with knock sensors that detect knock and adjust the timing to eliminate knock/pinging (regardless of fuel type/octane rating). The manual states that you can run 87 octane fuel with no problems, however they do recommend running 91 for "best performance", but 91 is not necessary. In my own and others experiences, 87 is perfectly fine to run (remember that the owners manual says its ok to run 87) and I notice no differences in power or mileage. However you may have different results.

Now if you run 87 and are having issues with knock/pinging then the easiest thing to do is to switch to a different grade of fuel and see if that eliminates the issue. If it does, then continue to run that grade of fuel, problem solved. If itdoes not then there is a good chance the problem lies elsewhere and that will be a different story. Either way run a higher octane fuel first and see if that clears the issue up.

Ariyanna

That's what happened to me I ran switched from 91 to 87 and the car started to knock so I changed back to 91 and the knocking went away almost instantly

angmedic91

iTrader: (5)

Would this knocking or pinging cause a CEL code P0330? I'm having or had this same issue, when i was accellerating up a hill I would hear rattling from the car, I thought it might be my Cat. Convert., sort of sounds like a rock tumbling in a can. I also poured some seafoam in the gas tank and it seemed to rattle more on incline with acceleration, then had a CEL, two codes, P0171 and a P0330. The P0171 is a MAF sensor issue and I have a new sensor ordered, but wondering if the P0171 caused the P0330 or did this rattling cause the P0330 code. I also had my valves adjusted prior to the P0330 code. I reset the ECU several days ago and havent gotten a CEL yet, knock on wood.

topgun129

Hi All,

Thanks for the responses. I will definitely change the octane grade and report back.

Thanks again!

Bedore

Yes. P0330 indicates a malfunction in the Knock Sensor 2 circuit. If you have a bad knock sensor (or more likely a bad wiring harness) you will have some knocking as the ECM is not getting proper input from the sensor, and it cannot adjust the timing correctly to eliminate the knock. Knocking happens more frequently when the engine is under a heavier load (hard acceleration, or going up an incline). To me it sounds like marbles rattling around in a can. You may notice other symptoms as well such as hesitation and/or lack of power. Once you replace your MAF sensor re-evaluate how the car acts and if it still knocks or not and look for the CEL and the P0330 code. I am unsure if a bad MAF would cause the ECM to toss up a knock sensor code or not.

Sometimes the code can be intermittent, or sometimes it will light the CEL all the time. But if it's showing you that code, then you probably have a break in the wiring. It's common on these. Do a search on it if you get a spare moment.

Thats your experience. If your motor knocks on 87 and switching to a different octane fuel fixes it, then great. However saying that you need to run 91 all the time and that 87 causes the motor to knock, is incorrect. Myself and many others run 87 with no problems (the 87 I run is also 10% MTBE). YMMV. Gas is different all around the country. But the manual says it's ok to run 87, so thats what I run. I have noticed no differences between 91 and 87. When I first got my ES300 I ran 91, then tried a tank of 87 with no knocking and no mileage differences, so I opt for 87.

To the OP, let us know what happens when you switch to a higher octane fuel.

Ariyanna

Dude I know our cars are made for 87 it says it right in the manual so I switched from 91 to 87 since I read on here that it was fine but when I did the engine started to knock, so I switched back to get rid of it since it bothered me.

Bedore

Yes I get that. As I said before, that was your experience; that will not happen to everyone. You specifically said 87 will cause the motor to knock and you have to use 91, which was incorrect. I was just saying that that is not always the case. I didn't want someone to read your statement and think they needed to run 91 when they didn't, unless of course they had knock issues, and changing to a higher octane fuel eliminated the knock. That is all.

angmedic91

iTrader: (5)

I did research this before hand, and causes could be knock sensor itself, wiring short circuiting and even a bad coil can cause knocking which in turn could cause a P0330. I had just taken my car into the dealer 2 weeks ago and they replaced my fuel filter, dumped, filled and bled my brake system, cleaned out my MAF sensor and lastly did a valve adjustment. The later of the two were done because I had a P0171 code and ran me just under a $1000 dollars. Now, I got another P0171 and a new P0330 code. I'm just wondering if when they did the valve adjustment, did they have to move or unplug my knock sensor, now causing a short? I read that to have the dealer replace the knock sensors and wiring will run around $800 dollars. All of a sudden my ES300 is costing me and is now due for an oil change at that. In one month I will have spent 2 grand to keep her running and CEL free. WOW!

Bedore

The knock sensors should not have been disturbed during the valve adjustment. The knock sensors are located under the intake manifold. To replace the sensors or harness you would have to remove the intake manifold which is quite the job but not extremely difficult for those inclined. Mostly it's just time consuming. Most likely you have a bad knock sensor or a short in the wiring (based on the code you are getting). Sorry to hear of your troubles but it sounds like your Lexus is beginning to nickel and dime you to death. If guess now you have to ask yourself if it's worth it to you or not.

angmedic91

iTrader: (5)

Well, I think its worth it. Ive heard these engines run for ever if taken care of. If I had the money readily available, then to replace the knock sensors would be no big issue, but money is tight and now the holidays are coming around. I also will be needing to get a new cat. converter and thats like $1,300.00 dollars. I just got it smogged and the Hydrocarbons are at max at 15mph, I'm told it might be time to get a new cat. I have two years until my next smog check.

chachacha

I've just heard the knocking sound today and CEL came up...im running 87 almost all the time...
anyknow where is the location of the knock sensor? MAF sensor is the one located on top of the air filter, correct?

Webs

hello top gun did u find solution to your prob my car jus developed that prob pliz help