nyxnyx

i have a 1999 gs 400 i find that when i excillerate hard i hear a rattling sound more like tapets ,has enyone experienced this the car has 50000 miles ,

RRocket

More info...where is rattle coming from? It could be detonation, which almost sounds like someone shaking a paint can...but we need more info..

rominl

iTrader: (4)

yeah definitely more info.. where is it from, within cabin or outside? does it change with speed? brake? turns? plastic or metal?

nyxnyx

yea it does sound like someone shaking a empty paint can it seams to come from drive train area and only when i excelerate hard then it goes away .seems to come when under load never while normal drivind and when top speed is reached it disapears lasts for seconds when excelirating thanks for the help

DaveGS4

iTrader: (2)

Sounds like detonation (pinging), especially since its under hard load.

What kind of gas do you put in your GS? Does this happen all the time or just recently?

XYZLexus1

I agree, definelty pinging or predetonation. Your engine is equipped with two knock sensors. One behind the power steering pump and one behind the starter. They should retard your timing when vibration/ pinging is felt. I feel they are working on your car. You state the pining goes away, this would indicate the sensors are picking up the vibration and retarding the timing.

If it makes you feel better I have heard alot of Japanese cars ping on acceleration including GS300's. Try this cruise along at a steady speed than quickly accelerate, you will hear the ping. You will also notice it will only ping after the car reaches steady state temperatures.

The manner in which Lexus get the power 220 hp out of such a "small" engine 3.0 liter is by having a high compression ration 10.5:1. Most US made cars use larger engines but have lower compression rations 8.5:1. The downside to the higher compression ratio is you have to use premium gas and pinging is an issue. The knock sensors should eliminate it by retarding the timing. Retarding the timimg cost you power.

Pinging if excessive will eventually burn the valves. I do not feel yours is excessive because you hear it and it disappears, if it were constant than you would have an issue. Once again these are my thoughts so you may want to investigate it further.

nyxnyx

thanks for the replies ,i have had the car for three months and hve noticed it from day one like i say it only hapens under load and for a few seconds i am in canada and the fuel i get is 91 octane from reading the posts it seems you use higher octane fuel in the us or parts of it i figure from reading your replies that it is minor ,or so i hope