Questioni have a 1990lexusls400. car has 215,000miles i have been hearing a knocking or pinging noise from engine lately.I also notice that it occurs mostly when car has been running for awhile and has gotten hot. Temperature gauge is reading perfectly so the car is not overheating or running hot. Please some advice.
Answer*Too much carbon build-up in the combustion chamber (Seafoam through the intake, or water injection will clean it out.)
*EGR valve is stuck closed (Clean it, the Idle valve & Throttle body all by hand - it's routine maintenance on any car that has EGR, the carbon in the exhaust gas cakes on everything, eventually sticking them in place.)
*Spark plugs are too hot (Replace them with the specified NGK, or Denso spark plugs)
*You're running lean (Check for vacuum leaks, check that there is correct fuel pressure @ the fuel rail & that the injectors are operating correctly)
On a side note. Please understand that the temperature gauge is a representation of what the coolant temperature is after the entire engine loop. Don't think that you can't have the farthest cylinders from the coolant temp sensor that runs your gauge overheat & then the coolant cool back down to normal before it gets back to the gauge.
;)
It's true on all engines.
Just keep up with your oil changes & change the fluid in the transmission every other year atleast once.
