drew028

400rmp is a low idle doubt it would be mounts. I bet ur clock light is dim also? I have a similar problem my idle is never consistent Sometimes low around 400 and other times is ok. I will be doing plugs and fuel filter. Also going to check the pedal position sensor just because when coast at 30 40 my idle will go down to 800 or so and when i tap the gas barely it will coast at 1000 or so.

CARSnGUNS

You've got transmission problems. The clutches or bands are grabbing and not slipping the way they are suppose to. When you place it in neutral it sounds smooth and normal because everything is free to rotate. It's the same principle as a manual tranny...put it in neutral and realease the clutch a fraction, no problem. Choose any gear and do the same...you get grab, chatter and a low, rough idle. I would suggest you bring it in to a specialist and have them look it over before it gets worse and more expensive to repair.

vmirjamali

what's tb stand for btw? I know maf is mass air flow sensor and I cleaned that out already. Thanks

sakataj

iTrader: (182)

TB = throttle-body

vmirjamali

Alright I finally got time to do this, and my god I don't think anyone had cleaned the throttle body before, it was just bad. I cleaned it using throttle body cleaner and the car runs much smoother now, but after some time the car went back to rough idle's after the car "learned my driving".

Does the gs400 have a egr valve, and if so how do I get to it, to clean it? At this point that's the only thing left to clean.
Thanks

Damian@FI

I recently had this issue. I had the MAF, THrottle Body and Air filter cleaned, oil change and it was all good, idle raised slightly, no more low idle under load and all smooth.

Hope this helps,

d.

JiBBeL

iTrader: (2)

Engine mounts, plain and simple. The car is SUPPOSED to idle at 400 with little to no load. It's not low, but your engine mounts are shot and you can feel the vibration and hear the hum. I got my engine mounts replaced with OEM and now it's dead silent and has zero vibration at idle.

vmirjamali

Jibbel, the car runs fine in idle after I reset the battery for about 50 minutes. Perfectly fine with no issues under load or during idle. Then after it "learns" how I drive, it goes back to the rough idle. How can it be engine mounts when it's working perfectly fine for the first 50 minutes ?

GS4_Fiend

iTrader: (22)

On the 2GS there is no EGR valve.

Rick James

Trust me its the engine mounts!

Sampak

I have this problem almost to the T. At idle in gear, and even in P/N the engine vibration is noticeable but not rough, however I'm pretty sure it's not supposed to be this much considering it's a Lexus. My gut is telling me I've got an expensive bill for the engine mount(s) waiting around the corner.

However unlike the OP I have not yet checked the MAF, TB, or plugs. I don't know all the history of the car to know if it's worth changing the plugs but I believe the previous owner stated they looked clean. I guess before anything, I should have these things squared away just to be sure... dur durr.. But like the OP the car is extremely smooth once at speed, so that keeps making me think it's gotta be the mounts and not the plugs/maf/etc. Guess I'll find out soon.

SC4Paulo

iTrader: (2)

I have the same problem, when I'm stopped at a light or something the car shakes more than I would like, from personal experience of shot motor mounts and transmission mouts I suspect this is the culprit, I plan to replace it after undo my ball joints and caster bushings. you guys want to hear some good news? With our clublexus discount through Sewell 2 front motor mounts and rear motor mount aka transmission mount is under $300.

rgrant159

You guess who are getting a rough idle.. maybe you should check into getting the center support bearing looked at... I had the same issue.. and it can cause a rough vibration during idle...

Sampak

Welp, I cleaned up the MAF and the throttlebody/plate only ( I just removed the intake hose and box) and whatever I could reach inside. It was definitely dirty but nothing that in my opinion should be causing a rough feeling idle (no large chunks or pieces of gunk). I had to disconnect the battery for 10 minutes and then start the car, so it idled up high ~1500 RPM cold, then calmed down. So far the only change I've noticed is that every time I start the car, it seems to 'chug' once before firing up; instead of a smooth crank-crank-VROOOM... it's crank-crank-hesitate-VROOOM. Almost like just before it fires up, it gasps for air/fuel. But otherwise it's running as before, idle vibrations and all.

I guess I can tack on $300+labor (worse than I thought) to the 'to do' list on top of the already pending rear control arms, valve cover gasket(s) and possibly refreshing the steering rack bushings(?).