KTGS300

I am trying to get a clue / starting point on how to find the cause of this low idle issue on my '02 GS300. It runs fine for the most part except when braking and coming to a stop then engine would idle really low. It dips down to 300 RPM and feels like the engine is about to stall but doesn't. It only happens when the car is warmed up. Anyone has seen this happen, or experience it before?

vijayn

It sounds like your intake system needs cleaning, particularly the throttle valve area.
Remove the top manifold where it meets the throttle body and get some carb cleaner / intake cleaner and clean before and after the throttle valve. Also is your air filter dirty?

It could also be your coolant sensor or wiring giving incorrect values to the ecu. This sensor tells the ecu to lower or raise the idle through the throttle motor. Are there any codes?

2gz

I have the same issue when I drive and the car is warm and if I come to a sudden stop then the car will idle so low that it will die sometimes.

kevin3344

You probably have a vacuum leak. I chased this problem for months and every so often my car would idle very low or die at a stop light. It would immediately start back up though, so I didn't know what was wrong. Like you it only happened when the car was warmed up so it was hard to track down. Finally I took it to the dealer and when they inspected the car they found a cracked vacuum hose.

KTGS300

I finally had time to work on the car this weekend and tackled the intake / throttle area first. Throttle valve and plate was pretty dirty, so I gave them a good cleaning with throttle body / intake cleaner. Took the car out for a drive and it was running pretty rough for the first few minutes. Then it starts to settle in once the car is warmed up. I am happy to say that the car is idling smoothly now. I hope that was the problem and cleaning it was the fix.

Thanks all for your suggestions.

vijayn

Thats great news. Does your engine still run rough during warmup? Or was it just that one time after you cleaned the throttle?

KTGS300

Drove the car to work this morning and didn't noticed any rough startup. Like you said, I think it was from cleaning the throttle because I emptied like half of the can trying to get all the gunk out. So far idle has been smooth and also noticed accelerating from a stop is more responsive too.

lexo98

iTrader: (2)

DeanWeen

I think you very well may have found tha cause of your low idle. I for one am certain that I have a vacuum leak and have yet to find it. It's causing a super high pitch whistle. Today I went and bought a mechanics stethoscope to try and pinpoint the issue. I am responding though because two weekends ago in my 1st Gen GS300 I was out looking at houses and it died and wouldn't start back up. I had been dealing with a rough idle for quite a while. Thirty minutes later the car started right up and ran fine the rest of the day. I was still very nervous about trusting the cars performance so I didn't drive it for a few days until I could get in and do some work. Assuming it may be the fuel pump going out I purchased one but before installing it I took the throttle body off and cleaned it thoroughly. It was funky to say the least. I can honestly say though that since the first incident where it died I haven't dealt with a similar situation since. I will occasionally get a lower idle but I think that is due to the vacuum leak.... But the point is my confidence is restored in my 1GS3 so I took the fuel pump back and ever since I've been grateful that i didn't take that seat out and drop the $175 post in the gasoline just to realize I had the same issue. So for anybody on here ever complaining about rough idle at stop lights ou on cold starts or even after it warms up my advice will always be take the time to take the throttle body assis and clean it up like new and if nothing else you will know that you can rule that out if your problem persists. I'm always glad to hear about other folks getting their babies back on track. I especially love it when I hear someone say it's even more responsive and the issue has stopped. No matter what it is or what it costs (almost).

Toshi1

Had the same issues and found a vacuum leak in the box below the intake arm. Gave myself a reason to buy an intake and fixed the problem and got some more hp now too. While doing that clean your MAF and throttle body too.