acueto81

Hi everyone,

I own a 2011 IS 350. I love this car very much, and this is coming from someone who went from an IS 250 to an IS F to an IS 350. I had the Safety Recall DLG performed in October 2013 by the dealer, at about 25,800 miles. Right away after picking up the car, I noticed a rough idle condition when at a stop sign or stop light. I had never experienced it before. I brought it back to the dealer a few weeks later, and they didn't find any issues.

The issue continued however, and in March 2014, I again brought it to the dealer's attention, and they could not reproduce the issue on a test drive in which I participated. No repairs were done.

I brought it back to the dealer in April; again, complaining about the same issue. This time, they replaced the motor mounts, thinking that the rough idle condition was caused by worn motor mounts. The dealer seemed really reluctant to do more in-depth diagnosis beyond reading codes - and no codes were being generated. After I picked up my car post motor mount replacement, the engine was running poorly, and now the CEL and slip indicators were illuminated. I brought it back to the dealer the next day, and they found the codes were P0101, P0171, P0174, and P1170 (all codes having to do with a vacuum leak). They found that the air intake hose was not seated all of the way to the air box, and fixed the issue. They said that what probably happened was that the hose was loosened as a result of the DLG recall, causing a rough idle condition, but not enough to trigger the CEL. The replacement of the motor mounts probably knocked it even looser, triggering the CEL.

The idle after this repair was improved, however, not quite as smooth as before the DLG recall. Back in May, I had the same dealer recheck the engine mount repair, and the health of the air intake system. They ran some tests, and they came back saying everything looked normal. They explained that they even tested two different IS 350s, and their idles were the same as on mine. They said that what I was probably experiencing was carbon buildup, which is more common on 250's than on 350's (due to the injectors), but can still happen on 350's. Bottom line, the idle on my car was deemed normal.

Since then, the issue has continued - at an extremely intermittent rate. I took the car to an independent mechanic, and he said that what I was experiencing was indeed carbon buildup. He recommended some procedures using BG products to clean the fuel system and engine, which could potentially improve the rough idle condition, but probably not by much. I told him I would do some research and think about it.

Soon after, I've tried putting in some Chevron Techron Concentrate Plus Fuel System Cleaner to a full gas fill up to see if that helped, but the condition didn't really improve. Note that I have always put in Chevron 91 octane in the car since I bought it. I don't skimp on fuel at all, no matter what the price per gallon is.

The issue has continued, and a few weeks ago, I tried taking it to a second nearby dealer. They were not able to reproduce the issue at all. They hooked up the car to a laptop and drove it around, and everything came back as normal.

The issue with the rough idle/shiver is so intermittent that I cannot pin it down to a pattern as to when it occurs. It is really annoying, however, and has been driving me crazy. No CEL or codes have come up. The engine hasn't stalled. However, the car still shivers/idles roughly at a stop. It sometimes starts shivering right away when coming to a stop, and sometimes starts 5-10 seconds afterward. Sometimes it doesn't do it at all.

Sorry for the long post. I'm just trying to get some help in potentially solving the issue, if there is any issue to be solved. Despite what the dealer and the independent mechanic have said, I'm still not quite convinced that the issue is normal and due to carbon buildup. For one, the issue started after the DLG recall, and two, I haven't heard complaints from IS 350 owners (from browsing forums like Club Lexus) about carbon buildup. My questions are: does this rough idle/shiver in fact point to carbon buildup, and therefore is normal? could something have gone wrong during the DLG recall to cause this rough idle/shiver condition?

Any help would be greatly appreciated.

Thanks!

idoke1

iTrader: (5)

Check your throttle body and maf sensor. Make sure it's clean. Also try resetting the ecu.

Gville350

iTrader: (10)

^Yes, right after I had my "cam ratle" recall done I reset the car (just disconnected the battery for 20 minutes) and that forced the car to re-learn my driving habits. It definitely helped me in my case.

Let ask you this, how many times a day do you hit WOT? Do you just drive inner-city type bumper-to-bumper traffic alot? I feel opening up these things can really help the motor maintain better overall health.

acueto81

Thanks guys for the suggestions.

I'm going to try to reset the ecu by disconnecting the battery this weekend. I just remembered that when I did the DLG recall, they replaced the battery under warranty at the same time. I'm thinking that since the car was idling roughly because the air intake hose was not seated all of the way to the air box at the time of the recall work, causing a vacuum leak, this might have "taught" the computer an improper idle - with the new battery installed. I'm optimistic resetting the ecu will solve the issue. [crossing fingers]

Gville350, I do WOT every other day, maybe a couple of times a week, max. Unfortunately, I live in Los Angeles, so bumper to bumper traffic is a way of life. I mostly get a chance to do WOT when I get on a freeway on the ramp, and when traffic is light on the freeway. Going through this issue has taught me that going WOT every once in a while allows the car to stretch her legs, and like you said, help maintain the health of the motor.

I'll update everybody after I reset the ecu and have a chance to drive it around after.

Thanks again for the replies!

Gville350

iTrader: (10)

^Hope that fixes it! Remember, immediately after reconnecting the battery, let it idle for a few minutes and then go out for a drive how you would want the car to perform and shift. It re-learns pretty quick; about 10 minutes-worth of driving I'd say.

acueto81

I reset the ECU on Saturday 7/19 by disconnecting the negative cable of the battery for 20 minutes, and after, letting the car idle for about 10 minutes before taking off on a normal drive that included both surface streets and freeways.

I've driven the car around all weekend: it still idles roughly/shivers at times when at a stop. It may be too early in the reset process to reach a conclusion about whether the issue has been fixed or not. I don't know.

I also forgot to mention that throughout the whole time the car has always idled around 650 RPM with the A/C on, rough idle/shiver experienced or not. The needle on the tachometer has never fluctuated wildly, even when the rough idle/shiver is experienced. It stays consistently around 650 RPM. Putting the car in neutral or park smoothes out the idle somewhat.

I’ll continue driving the car and provide updates.

Gville350

iTrader: (10)

^Try giving it more time to see if it helps.

GL!

acueto81

For the last day or two the rough idle/shiver has turned more into more of an intermittent vibration feeling at idle. Seems to happen when the car is warmed up, and in Drive or Reverse. However, it can also happen during Park or Neutral - just not as often or as pronounced.

When I was resetting the ECU over the weekend, I did notice a light rattle in the engine. Pressing down on the engine cover seemed to make it stop temporarily. This is something that I just noticed. At this time, I don't have a lot of information about it, and I am not sure if it as an isolated incident or related to the rough idle/shiver/vibration.

I've contacted Lexus Corporate to further document the issue, and to see if there is anything that they can do.

I'm beginning to think that something was not done correctly when they did the cam gear recall work last October. I already know that when the recall was done, the air intake hose was not seated all of the way to the air box. If they overlooked this detail, that means they *may* have overlooked something else. The car was running fine before the recall, and the very first thing I noticed when I left the dealer after picking up the car was a rough idle. Maybe something having to do with the timing or timing chain? I've never had any carbon buildup issues with the car. In fact, the word carbon was never mentioned until after the recall. The car is an IS350, and not an IS250, which I know can experience carbon buildup issues.

Any thoughts?

synrgy350

I remember having strange idle issues after my recall as well. I went back to the dealer and had them check out the car but they said they didn't find anything wrong. I ended up scanning the ECU with my tech stream and noting my fuel trims were higher than normal, meaning there was an air leak somewhere in the engine. I ended up replacing the air intake manifold gasket and PCV valve myself and that eliminated most of the idle variation I was experiencing. Fuel trims still aren't perfect compared to before the recall however performance remains good so I didn't bother going back and complaining. Do you have access to a tech stream or know anybody that could scan your car for you?

Gville350

iTrader: (10)

Remove the engine cover altogether to see if that fixes the rattle. Just pull up on the cover itself; it just pops into a ball-n-socket type thing. Once removed, look for things that might be loose or dislocated. After I had my cam gear recall performed, I did have two clips broken and a portion of plastic tab that a wiring harness uses to attach to the motor broken off. Other than that, mechanically the car is solid.

GL!

acueto81

An air leak seems possible. Like I said, I never experienced this issue before the recall. From looking at the Technical Instructions for the DLG recall, it seems like a lot of gaskets were touched (and replaced). Maybe there is a small leak somewhere that's not enough to trigger a CEL but enough to make a difference in idle. Like I mentioned earlier in this thread, we already know that a vacuum leak was caused by an air intake hose not seated all the way to the air box, causing unmetered air to enter. (This issue has since been corrected, according to the service dept.) Maybe there are other leaks as well.

I'm back in touch with the service manager at the dealer that performed the recall work. I'm documenting the conditions during which the rough idle/vibration is experienced. Eventually the car will go back to their shop for further diagnosis. I'll bring up looking at fuel trims and inspecting for vacuum leaks. Unfortunately, I do not have access to a tech stream. I let the dealer's service dept. maintain my car. However, this issue (and the service dept's difficulty in pinpointing the issue and its cause) has forced me to learn about the workings of the car so I can talk intelligently with them. I guess this is a good thing in the long run!

acueto81

Actually, strangely, the rattle seems to have disappeared. I can't seem to reproduce it. I'll alert the tech about it when my car goes back to see if he can reproduce it.

I'll continue to keep everyone posted!