Intermittent Shuddering/Misfires, rough idle are issues starting to appear on GS300s/350s predominantly.
Notice the pattern on the above previous posts....


Caused by: Carbon Buildup in the valves.


Some misfires triggers a CEL, some don't.
I have been researching this issue for months now; I personally believe that this is an early engine design flaw related with DI engines.

Dealers are dealing with this issue depending on the gravity of the problem.
Ask your dealer about 3GS Carbon buildup issues.

 

Would the recommended fuel injection service at every 30,000 miles be useful for this I wonder?

 

it would...including regularly dumping a can of injector cleaner, high octane fuel grade.

spirited driving is also recommended on ANY DI engines to prevent excessive carbon build-up (think autobahn storming).

but if misfires are fairly occuring regularly with rough idle and CEL issues; this requires more than fuel additives...again, dealers are dealing with carbon buildup issues depending on the severity.

 

I was able to get the car to shudder for a while as posted in this thread today by just revving the engine high while in park and then letting off the gas pedal. When returning to regular idle it shuddered noticeably for some time.

I tried to replicate it doing the same thing a few more times but I couldn't.

I happened to have an OBDII reader hooked up to the car while I was doing this, and I kept scanning and there were never any codes. I was actually trying to see if I could catch some kind of pending code so I'd have something to bring to the service manager who is under the impression that carbon buildup problems are only an IS issue.

I bought a bottle of Regane that I'm just going to try to see if it helps any, but I just filled up the tank yesterday and the instructions say to put it into a near empty tank THEN fill up (to mix thoroughly) so it might be a while until I actually get through the tank as I don't drive much. Not sure what harm there would be in just dumping it into the fuel tank and then rocking the car back and forth and up and down on it's suspension for a few minutes so as it make it slosh around and then just driving it normally. The gas has got to be moving a lot just from stopping and going...

Part of me doesn't even want to try the regane in case it actually does something and delays my actually getting some misfire codes. :|

 

Dont worry about not being able to "replicate a misfire", or no CEL after a misfire....

Dealers have proprietory scanning software/devices that are far more advanced than your regular off the shelf CEL scanner.

Dealers can/will be able to read ALL misfire codes regardless whether or not CEL event occured. Lexus is able to read the EXACT misfire scenario, and get a full read-out on a "pattern".

Dumping a can of fuel additive won't hurt a bit.

Next time you bring the car in for service, mention to the service tech that you noticed a misfire/hesitation, and they should hook your car up on their scanner

 

I did just have it in for them to try to service this issue, and they had it hooked up to techstream and told me multiple times the only thing they found were the inaccurate readings from the O2 sensors. They performed the TSB replacing the O2 sensors and ECU.

Either they didn't have it hooked up for very long, or didn't get lucky enough to have it act this way while they were doing it or just didn't try very hard. The service adviser seems willing to take it back again and take off the intake to check for carbon, so I'm going to give it a bit and have them do that... I'm not sure how much they'll actually be able to see with just the intake off, unless what he meant was actually looking at the intake valves but even then I'd expect the problem to be more in the exhaust valves.

In the meantime I'm going to do my part and drive the snot out of the car with the pedal to the floor at every stop and throw the regane in there. Given that I don't have any codes, I'm guessing that the buildup (if it is that) is not that severe and perhaps just driving hard on a few tanks of regane will get things normal again.

If anybody else's service manager has diagnosed/fixed carbon deposits on the GS it might even help if you could forward me your dealership contact info and I can put mine in touch with them.

 

^no worries....

as long as Lexus documented your issue/s.

just drive the car, and maintain normally.

the ecu, 02 sensor fix might do the trick for you

 

I've been trying to come to grips on what exactly it is with direct injection and the whole carbon thing. My research has shown that just about every manufacturer's DI engines seem to suffer from this design flaw.

It seems the problem stems from the PCV system and the fact that DI motors are not washing the intake valves with fuel, since the fuel is injected directly into the cylinder and not ahead of the intake valve as in a traditional FI system.

The PCV system is returning the unburned junk into the intake where the heat bakes it on and since the intake never sees any fuel none of the detergents in the fuel ever get a chance to clean anything up. I've seen pictures of some DI VW engines that scare the brown stuff out of me online.

After thinking this all the way through, I doubt that all of the PEA (techron/regane) in the world isn't going to do a thing if my intake valves are encrusted with junk deposits.

Is the only way to really diagnose this to tell them they have to remove the whole intake manifold and visually inspect the valves? They say they never have any GS with this problem, but lots of IS250s. The 3GR-FSE doesn't have secondary port injection like the 350 does, so it shares more in it's design with the 2.5L engine than the 3.5L engine. It could be that 350s don't get it nearly as much because at least at some points the intake valves are washed by the port injectors. There are also far more 350s in service than 3GS 300s now, which might explain the lack of seeing the problem on the GS.

I think any kind of carbon issues that are covered under TSIBs for the IS250 should also apply to the GS300 but I can't find anything online that specifically addresses the problem in either vehicle.

I'm going to go ahead with the regane treatment for a tank before going after Lexus again but I get the feeling that they are going to end up having to crack my engine, they're going to find a dirty mess and I'm going to be in loanertown for quite a long time. That in itself is fine, but what really gets my goat is that there doesn't seem to be any permanant fix for it and I'm not even sure what can be done to prevent it from recurring if all of the fuel treatments in the world won't help.

Now, I suppose it's possible that the new ECU does more than simply make the engine compatible with the new type of O2 sensors that are replaced as part of that TSB and that they actually change the timing so the intake valve stays open a bit longer after fuel injection so that some of the fuel mixture is pushed up past the valve before it closes but there isn't any information about whether this is true or even plausible.

 

This hezatation has happen to me twice at the same stop light, and the stop light is on the top of a hill...I use chevron all the time and no modifications on the car...

 

the shudder happened to me just 10 minutes ago. this time the CEL came on and the orange circle with the ! in the middle came on too. and the dash display said "CHECK VSC" i gunned it from the stoplight to see if it would do anything and after a while it all went away. dunno if this helps diagnose the problem but after reading BinaryJay's post it seems that this is something i'll just have to deal with =/

btw thanks BinaryJay for doing all that research and contributing to this thread. it's really helping me understand the DI system more and i'm sure you're others are learning a lot too.

 

I think this has something to do with the fact that we had awd versions, not sure if all have the automatic stick feature I think this has somethingto do with it as well

 

I've gone through half of my tank of Regane (yeah I know, I don't drive much... this tank is taking forever to empty even though I am gunning it in power mode everywhere I go... seems like my new O2 sensors and ECU are doing me some favors in hard driving fuel economy at least).

So far I have noticed no change in the behavior of my car, it still does the weird shuddering thing when slowing down... almost feels like it's pulsating a bit and I don't think it's brake related since they are smooth as ice during normal braking, it's only when slowing quickly from a higher engine speed. Also get the slight shakes now and then even though it's nice and warm out.

Still not blessed with any kind of CEL. After I'm through with this tank of glass I'm going to ask them to inspect my valves. Something I thought they should have done the first time they had it in, instead of just throwing parts at it (though I always appreciate nice new parts...).

I wish that was me. I would have stopped and hooked up my code scanner that I keep in the glove box right away.

 

The exact same thing happened to me today, except after the light turned green,my car would not accelerate past 20 MPH. My car has done the "shudder" thing before, almost once a month, but this was the first time it did this. I have taken it to the dealership but they told me the same thing it sounds like they've told everyone else with this same issue: "We couldn't duplicate the issue." I find it really curious that so many people have reported having experienced it, and Lexus feigns ignorance on the problem. Has ANYONE been told by Lexus that they were able to duplicate the shudder and given an explanation?

 

a one time major shudder is NOT highly definitive of Carbon buildup....
lots of things can cause shuddering.

just observe the vehicle for now; if anything make sure your dealer is in the loop.


I believe you resurrected my very first post regarding possible carbon issues with the 3GS
(post #31....1/8/10)
It took time to put all the symptoms together before Lexus turned out with their Carbon Buildup TSIB. I was just persistent and took time comparing carbon emissions on my other DI powered autos to prove my case. Prior to the TSIB, my dealer had to prove my issue by opening a TAS (Technical Assistance Service)case to Lexus before working on any type of fix/repair.

more related reading on carbon buildup:

check out post # 42, #45, #54, #57....notice the pattern prior to these posts.

https://www.clublexus.com/forums/gs-...m-spike-3.html


Twong1200 also posted the latest TSIB regarding Carbonbuildup issues:

https://www.clublexus.com/forums/gs-...-build-up.html

Goodluck!