Gs300 Rough Idle

[tonyricha]

Hi all, I own a 2002 GS 300 with a BRG LPG gas conversion now having covered 115,000 miles, the idle speed has always been low with the occassional missfire when hot, the car now cold starts perfectly and runs at 1200rpm for about 10 seconds and then tries to idle at about 400rpm which causes it to stall, it then will not re start for almost 3 mins, spinning over at high speed but not firing. As I am unsure what the cause is I have had the gas system completly disconnected but the problem persists. I found the local Lexus agent very un helpfull and so have had the car diagonsed by my local garage, local Toyota garage and Torque Developments Int who all tell me there is no fault except the idle speed, which is non adjustable is too low. The throttle boby has also been stripped and cleaned but made no difference .

Does anybody out there have any ideas how or who may be able to help me PLEASE?

[aido]

Might be worth trying http://www.mkivstore.com/ - they are Supra specialists and know the 2JZ engines inside out - possibly they may be able to offer advice as they do a lot of work on these engines, also may be worth trying a guy called Chris Wilson as he also does a lot of work on these engines and is known as an expert among the Supra guys - his info is here - http://www.mkivsupra.net/vbb/member.php?us...=Chris%20Wilson

Also may be worth looking at this thread - http://www.mkivsupra.net/vbb/showthread.ph...hlight=low+idle

[ColinBarber]

Who stripped the throttle body? Was the throttle position sensor set up correctly? Has the ECU been checked for any stored error codes?

Is the Air Con switched on? If not then turn it on, that may keep the idle speed up enough to stop it stalling. You may need to let it idle for 15 mins. for the ECU to fully adjust, or better still drive around and STOP is each junction and put it into N and allow the idle adjust (you have to be at a standstill for this to happen).

[IanCornwall]

I keep getting told that there is no adjustment for tickover on a GS300 Mk1

But no one has managed to tell me why when I adjust the small allen key grub screw on the throttle linkage I can set tickover wherever I want 500 rpm to lots of rpm

In fact some people tell me that the screw doesnt even exist and I must be hallucinating, but it is still there with a 8mm AF locknut

Is it a tickover adjust or is it to set the throttle buuterfly to the throttle sensor in some way ?

[ColinBarber]

I keep getting told that there is no adjustment for tickover on a GS300 Mk1

But no one has managed to tell me why when I adjust the small allen key grub screw on the throttle linkage I can set tickover wherever I want 500 rpm to lots of rpm

In fact some people tell me that the screw doesnt even exist and I must be hallucinating, but it is still there with a 8mm AF locknut

Is it a tickover adjust or is it to set the throttle buuterfly to the throttle sensor in some way ?

There are some mechanical adjustments, certainly on the older vehicles, however the ECU makes adjustments to correctly set the idle speed. So if you speed it up the ECU will just slow it down. You get to a point where the ECU runs out of adjustment itself and therefore you can influence the idle speed.

However if the idle speed is incorrect this means either the ECU hasn't set it yet (e.g. after a disconnected battery) or it cannot. If it is the latter then something is wrong, e.g. blocked idle up valve, dirty throttle body, incorrectly adjusted TPS, faulty throttle motor etc. and this fault should be found and corrected rather than adjusting something else.