bciesq Posted January 25, 2007 Posted January 25, 2007 It sounds like a classic case of pinging. Generally, the knock sensor in a modern car can !Removed! timing when this happens to the point that is almost unnoticeable, but if your combustion chamber has a heavy layer of carbon deposits then it can raise your compression to a level that is beyond the range of the sensor to compensate. If you run cheap low grade gas and make lots of short trips, you can get carbon deposits -- even in a Lexus. Because higher octane gas is more resistant to pinging, you are able to "fix" the problem by running that. I can think of a few potential remedies. (1) Keep running premium gas -- classic case of "Doctor, it hurts when I move my arm like this." Doctor: "Then don't move your arm like that." (2) The knock sensor may be bad and need replacing (rarely happens). (3) Clean out the carbon deposits. In my '73 VW, I can pour a *small* amount of water down the carbs with the car running and the resultant steam will blast the deposits off the wall of the combustion chamber. It's actually kind of fun to do. In a modern car, you are left with a using various additives. My favorite is Sea Foam. The easy, but less ostentatious, method is to put a bottle in the tank when you fill up with gas. The slightly more difficult way is to tap into the brake servo line and let the car suck up the Sea Foam until you see white smoke come from the exhaust -- then let the car sit for 15-20 minutes and drive it until it stops smoking -- and trust me, it will put out more smoke than James Bond's Aston Martin for a few minutes. Your neighbors will love it.
realkevin Posted January 25, 2007 Posted January 25, 2007 I had the exactly SAME problem. It turned out to be misfire, bad mass air flow sensor. I replaced it and the problem solved.
tmastres Posted January 25, 2007 Posted January 25, 2007 Heres a link to a very straightforward process for cleaning your MAF. I've yet to do it but ut seems quite simple. http://www.lexusownersclub.co.uk/knowledge...p;id=50&c=9
bciesq Posted January 26, 2007 Posted January 26, 2007 Heres a link to a very straightforward process for cleaning your MAF. I've yet to do it but ut seems quite simple. http://www.lexusownersclub.co.uk/knowledge...p;id=50&c=9 Just be careful to avoid touching the element -- its very fragile. Also, don't skimp and use the rubbing alcohol under the sink -- it has moisturizers and will do more harm than good.
mikey00 Posted January 26, 2007 Posted January 26, 2007 Hello, maybe anyone can help, I have searched and no luck. I have an 01 Lexus rx300 It has been to the dealer 4 times and they can't figure it out. When I have 87 fuel in the car it sounds like a bunch of cans rattling under the hood when I accelerate, especially up hills. When the car is on but not in drive I can rev all i want and the sound doesnt happen. Then when I put 93 in the car almost no sound occurs, only slightly which may just be from left over 87. Im not sure what it could be. THey thought maybe air/fuel ratio so they reset the pc's config and that didnt help. The checked and see if it was the o2 sensor and that wasnt it. They don't know what they are doing obviously. Maybe someone here has had the same issue and can help. They say the car needs 93 but its a lie, I've asked a Lexus Dealer and it's fine to use 87 as the manual says also. SOMEONE HELP, the sound is driving me to sell the car. Just search this forum for "pinging". You will get many hits on others who had the same problem. I am betting on the knock sensors. Cheap low grade gas is all my 2001 RX gets and I am over 100K without any problems.
bciesq Posted January 26, 2007 Posted January 26, 2007 Just search this forum for "pinging". You will get many hits on others who had the same problem. I am betting on the knock sensors. Cheap low grade gas is all my 2001 RX gets and I am over 100K without any problems. Just curious, but is your driving mostly short, low speed trips, or is it mostly highway, or is it a blend?
Karl K Posted January 30, 2007 Posted January 30, 2007 Warranty still good, but MAF or O2 sensor not covered under Powertrain. I am hesitant to go right now and get it replaced because I am currently not hearing it. Could it be because the whether is around 15-25? When it's cold, it seems like it's not doing it. Could that be? If thats not possible than that means the cleaning worked. Did that problem come on slowly or did it happen suddenly? If it happened suddenly it is likely a sensor malfunctioning. If it happened slowly, over a long period of time, it could be carbon build up. hope this helps Karl
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