moune Posted May 20, 2005 Share Posted May 20, 2005 I have noticed that my engine makes a weird knocking noise when I am driving it. I don't know exactly what it is and was told that higher octane fuel will help remedy that. But since it is a LS, the highest octane is required already. So what is the next step up to take care of this problem. Please help. Quote Link to comment Share on other sites More sharing options...
VMF Posted May 20, 2005 Share Posted May 20, 2005 do you have a check engine light on? when the knocking occurs? when you press the gas pedal or you hear it on a permanent basis? Quote Link to comment Share on other sites More sharing options...
moune Posted May 20, 2005 Author Share Posted May 20, 2005 do you have a check engine light on? when the knocking occurs? when you press the gas pedal or you hear it on a permanent basis? Well I disabled my check engine light when I install a new instrument cluster, because it stayed on all the time. It starts to knock when I give it gas. Quote Link to comment Share on other sites More sharing options...
larryp Posted May 20, 2005 Share Posted May 20, 2005 Suggest you enable light and diagnose problem based upon code given. :whistles: If you're running the high octane already, you have another issue that may be identified by the trouble code. Quote Link to comment Share on other sites More sharing options...
lexusjohn Posted May 20, 2005 Share Posted May 20, 2005 could be a faulty knock sensor :whistles: Quote Link to comment Share on other sites More sharing options...
VMF Posted May 20, 2005 Share Posted May 20, 2005 you dont have to enable the light to get the codes, connect the scanner to your OBD port located under the dash and get the codes. you can also reset the codes from the scanner. knocking under the acceleration means either low percentage of the gas in the mixture, bad gas, bad knock sensor and many other things. you have to get an error code to find out what exactly is causing this, it might be misfire in one or few cylinders as well. Quote Link to comment Share on other sites More sharing options...
JPI Posted May 20, 2005 Share Posted May 20, 2005 could be a faulty knock sensor :whistles: ← I never see the knock sensor on this vehicle goes out. Unless you replace the starter and damaged it. JPI Quote Link to comment Share on other sites More sharing options...
Shadow Posted May 20, 2005 Share Posted May 20, 2005 What year & mileage? Quote Link to comment Share on other sites More sharing options...
bossman Posted May 23, 2005 Share Posted May 23, 2005 Where are you buying your gas? Although you are putting premium in, is it from a reputable dealer? You may want to only get gas from a well-known chain. Also, best not to fill up your car when there is a tanker truck filling up the station's pumps as this will stir up all kinds of sludge in the storage tanks. Quote Link to comment Share on other sites More sharing options...
moune Posted May 23, 2005 Author Share Posted May 23, 2005 To answer the questions: 90' with ruffly 220,000, and I use Exxon, Chevron, or Shell premium gas. Quote Link to comment Share on other sites More sharing options...
Shadow Posted May 23, 2005 Share Posted May 23, 2005 Yep, early 90 is what I thought. Your problem lies in the ECU exasterbated by high mileage so checkout the TSB for your year. Quote Link to comment Share on other sites More sharing options...
VBdenny Posted May 24, 2005 Share Posted May 24, 2005 Are you saying that the computer causes problems on a 90 when it reaches high milage? I'll guess the TSB is the Technical Service Bulletin? Where do you find that? Quote Link to comment Share on other sites More sharing options...
Shadow Posted May 24, 2005 Share Posted May 24, 2005 Are you saying that the computer causes problems on a 90 when it reaches high milage? I'll guess the TSB is the Technical Service Bulletin? Where do you find that? ← Both ECU & engine are the factors, and ECU replacement is the fix assuming the engine isn't out of wack. I found the TSBs on my AllData CD, and, the last time I checked, they were also readily available online and at the dealers. Check engine error codes first before doing any repair. Quote Link to comment Share on other sites More sharing options...
Shelly'sLS400 Posted June 1, 2005 Share Posted June 1, 2005 Are you saying that the computer causes problems on a 90 when it reaches high milage? I'll guess the TSB is the Technical Service Bulletin? Where do you find that? ← Both ECU & engine are the factors, and ECU replacement is the fix assuming the engine isn't out of wack. I found the TSBs on my AllData CD, and, the last time I checked, they were also readily available online and at the dealers. Check engine error codes first before doing any repair. ← I'm having the same type of problem. From idle, in gear, I get a little spark knock also. I'm running premium fuel and have no check engine light showing. Are you saying that the ECU is faulty because of high miles? I have 143k on my 90!!! Other than the little knock, engine runs great and plenty of power, fuel mileage is the same. Quote Link to comment Share on other sites More sharing options...
SRK Posted June 1, 2005 Share Posted June 1, 2005 According to our owner's manuals, a little spark knock under transient conditions is completely normal, as the ECU runs the timing up to find what grade of gas is being used. If the knock continues under load, that's a problem, but if only during a rapid throttle opening, it is normal. Many engines experience this, and it causes no damage whatsoever. If a tiny bit of spark knock was enough to damage a Lexus engine, I wouldn't have bought the car! Quote Link to comment Share on other sites More sharing options...
jzz30 Posted June 1, 2005 Share Posted June 1, 2005 do you guys have oil in there? Quote Link to comment Share on other sites More sharing options...
pgupta Posted June 2, 2005 Share Posted June 2, 2005 According to our owner's manuals, a little spark knock under transient conditions is completely normal, as the ECU runs the timing up to find what grade of gas is being used. If the knock continues under load, that's a problem, but if only during a rapid throttle opening, it is normal. Many engines experience this, and it causes no damage whatsoever.If a tiny bit of spark knock was enough to damage a Lexus engine, I wouldn't have bought the car! ← Quite likely, you need new spark plugs and cables. If so, you will find that over time, the problem will get worse at around 45 mph, 1800 - 2000 rpm. Quote Link to comment Share on other sites More sharing options...
ECUPirate Posted June 3, 2005 Share Posted June 3, 2005 Ditto that on the plugs and cables. My old Chrysler started acting up as 'pgupta' described. I thought my transmission was out of whack. Turns out it was misfiring due to worn cables. Quote Link to comment Share on other sites More sharing options...
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