fellow friends

my 1st time posting and would like to enquire if anyone had faced a similar problem as mine here as when i did a search not much info about it

ok here are the symptoms and my car description
it's an rx300 front wheel drive MCU10

when car travelling below 2K RPM and on an uphill i would usually get a knocking sound from the engine ...but once step on the pedal say over the 2K RPM the sounds dissapear ...interms of power and fuel consumption i don't see any loss in that ..but that knocking sound get worse during a hot day

items that i've done before the problem appeared
Changed my O2 sensors
plugs irridium denso
cleaned all the items such as ICV , TB etc etc

So upon checking by my mechanic here, via removing the plugs he noticed that the ceramic glow tends to turn red hence indicating no enough fuel running in ...hence causing the plug to glow red/orangy..so he did replace the fuel filter and cleaned the ICV hence the symptom went away for a couple of days and came back again ...

so now he mentioned it's could be the FUEL pump which he thinks is not the culprit but could be it ...why he mentioned the fuel pump is not the culprit : reason is when he cranks my car it starts upon the 1st crank and inorder to detect a faulty fuel pump you'll be getting bad cracking to start the engine ...another thing is he's suspecting the ageing fuel pump whereby causing not enough fuel pressure and causing the plugs to run hot hence the glow

Oh well i'm in a dilema and hope someone out here could shed some light to this following problem

TQ

 

Welcome to Club Lexus!

What octane gas are you running?

 

As hyperwish indicated, switch to higher octane.

The other possible causes would be engine running hotter at the top ... check oil level and coolant level. With the engine cold, open the radiator cap and ensure the coolant is all the way at the top.

IMHO fuel pump/filter is a reach if not a wrong diagnosis.

You did not mention how many miles ... if around 140k miles or more, your knock sensors may be on their way out and the ECU is doing what it is doing based on the signals from the knock- sensors. Again use this with caution as I dont want to send you on an expensive possible repair. I waited till my CEL came on.

Salim

 

hypervish /salimshah

thanks for the lead and i reply to you some of the items which may be needed to diagnose this matter

as for the octane rate : we are running ron 95 and 97 here in asia and more of i've tried both of these the knocking sound still persist. Even some say try changing maker Shell -- > caltex , esso etc etc and still persist , and even plonked in several type's of fuel injector cleaners and indeed the noise can be heard even clearer and loud ...

oil level and coolant level are never kept low ...had open the radiator cap and checked and yehh the coolant is also all the way at top ...

as for millage : it's about 115K KM.

but last saturday i decided to stick with what my mechanic recormended : change the fuel pump ..and once i've done this so far drove the car for a long distance trip of 350KM's and never had the knocking sound anymore ...but i'll still keep my fingers crossed as when the last i changed my fuel filter a few days it was fine and uplast after several weeks the knocking sound came back ...so that is why for this fuel pump change i'm just keeping my fingers crossed and hope that this is the culprit to this problem ...

the fuel pump used was not a denso made, but instead a BOSCH type which a higher rate sort of thinggy ...as the denso ones are pretty costly and some fake ones in the market too ..so i was told that BOSCH ones are almost the same rate with those denso made ones and indeed is much more cheaper in cost and works as the same as denso ...

anyway will keep monitoring on this matter and also same time hope others can chip in their findings here ..

regards