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Good morning everyone. So this is my first post. after about a month of ownership and lurking the threads I figured I would finally join and get some help. I bought the ls430 at the end of may. It has 76000 miles on it. Two previous owners. First owner was out of Florida and had all of the service (including oil changes) done at his lexus dealer. The gentleman was in his mid 50s and and took excellent care of the car. The second owner had the car for 1 year and there are no (car fax) service records during his ownership. The second gentleman was in his 60s and lived in manhattan NY. all adding up to two owners that loved and babied this car. after going over the car with a fine tooth comb It looks like I picked up a gem. Interior/exterior all immaculate. Under the hood pristine. The car literally looks like I bought it new. Now to the frustrating part. I have a SLIGHT rough idle. Only when the car is in park or neutral. It does not matter if the air conditioner is on or off. If it's in any gear and there is load on the engine it's smooth as butter. Like I said I've lurked the threads and already and picked up some ideas. so... I've cleaned the MAF and throttle body. Both looked decently clean but I cleaned them anyway. I have a fairly advanced code reader that will allow me to view codes, graph live sensor data etc. The only thing that seems to catch my eye is the bank 1 long term fuel trim stays near 0 and bank 2 is around +3-4 percent. I've checked for vacuum leaks but the hoses all look new. No cracking or swelling. Without a fog machine I can't be 100% certain I don't have a vacuum leak, but after thoroughly inspecting the hoses I'm pretty sure I do not. When I first purchased the car I unhooked the battery over night to allow it to learn my driving habits. I've driven the car 1700 miles. The car has had nothing but shell v-power in the tank since i bought it. And just to cover my bases I ran two sequential tanks with techron concentrate to eliminate the possibility of dirty injectors. That was about a thousand miles ago. Nothing has changed. I've had my dad put the car from neutral to drive and neutral to reverse while I look for engine movement and I see none, so I believe this is not an engine mount issue either. Going back to the code reader. Both upstream o2 sensors are cycling properly between .1 and .8 volts quite frequently so they seem healthy. Both downstream o2 sensors hold steady at .7 volt after they warm up. MAF seems to respond to quick snaps of the throttle. I have no misfires on any cylinder. I've checked after several different drives.
My gas mileage has me a little concerned too. I'm getting about 11 city and 19 highway. The highest i got after a 120 mile highway trip from NY to PA was 23. I've heard of these things getting upper 20s highway. I'm certainly no lead foot with this thing. I have 6 years to pay for it, so although I'm 27 I'm driving it easy as well. One final note. The rough idle is worse after 3-4 minutes of sitting Parked. Intake air temperature at that point is usually around 110 to 120 degrees depending on outside temp. It's been mid 80s to low 90s outside since I got the car.
So with all that in mind if anyone has ideas please throw 'em at me. Sorry for the long post. Just wanted to cover as much detail off the bat as possible.
Thank you gentlemen
Matt
Did you clean the "idle port" on the TB? Would not hurt to run a bottle of good fuel system cleaner through the car. I like the Dura Lube Severe Fuel System Cleaner. Walmart has it for $11. I run a bottle through every 5k miles. Techron is not a very effective cleaner but this is not your problem.
Another possibility is that engine temp sensor can fail without any code. This affects fuel to air ratio and you will not have a code. The temp sensor just seriously misreads the engine temperature. Your highway mileage is not good. I consistently get 27+ mpg on trips with my 04 running 5w30 synthetic on stock 17" MXV4's. This is on the a UL which is heavier than other models. The UL also lowers itself over 60 mph so this may help with drag a little.
It could also be failing O2 sensors but you should get a code for this. The poor highway mileage is a sign that you do have a problem. Engine temp sensor and pre-cat O2 sensors is where I would start. Post cat are only for emissions. RockAuto has good prices on the sensors as well. If the pre-cat O2 sensors have never been replaced I would go ahead and replace them both. The temp sensor is not expensive and also is an easy DIY.
It's pretty low mileage for this, but I'd consider checking, then replacing (if necessary) spark plugs. You air filter is new? I concur that it could be a partially clogged fuel injector. Edit: * Definitely select a high-quality fuel injection cleaner and run that at a minimum (or higher) of the prescribed concentration. Fuel tank additives for injection cleaning typically work best if added before you drive at highway speeds for extended miles since the fuel spray with cleaner added is constant and at the higher volume of spray with engine at full operating temp. If you can safely, don't be reluctant to open it up a bit too. The 3UZ-FE horses like to run.
Just an example of what our LS's are capable of mileage wise. This was the average over 82 miles from a business trip today. Highway mileage of course. AC on, 93 degrees outside, cruise set to 75 mph and stereo on. It's very impressive. The car gets better mileage now then when I purchase it 3 years ago at 104k miles. Blows my mind. Especially when it is only rated at 16 / 23. I really do believe my mileage went up a few MPG after I replaced my temp sensor.
Plugs are a possibility I considered. But it's hard to fork out $75 on a set of oem plugs this early for a "possible" fix. AFAIK the plugs are supposed to be good for well over 100,000 miles. Another thing that deters me from this is the fact that there is no misfires. The temp sensor is another possibility. Although if I hook the code reader up before I start the car in the morning it says engine coolant temp is about 5-6 degrees from outside teperature. And after the vehicle is fully warm it holds steady at 195 degrees. Does this seem correct? Also I was not aware that there is an idle port on the throttle body. I thought the drive by wire throttle setups didn't have one. Although I cleaned it thoroughly i will admit it was hard to see. I just pulled the intake hose off and got in there with some throttle body cleaner on a clean shop rag. Where roughly would i find the port? I was lead to believe the techron concentrate was one the the best injector cleaners because of its PEA content. But I'm willing to try others if you guys have had better success with them.
Honestly, I would do the temp sensor anyway. I think at 100k miles or so it should be replaced. Plugs should be done around 100k. Lexus says 120 but they need it by 100k miles. You won't misfire but the gap is large and there is carbon build up.
Ah ha. Thank you Lavrishevo. I'll have to pull the cover off the idle port and see how the little passages look. It will probably have to wait a few days but that's my next step. Thank you.
Ah ha. Thank you Lavrishevo. I'll have to pull the cover off the idle port and see how the little passages look. It will probably have to wait a few days but that's my next step. Thank you.
You are welcome my friend. Since the problem is worse after the car is warm I don't think this is your problem in regards to rough idle. When this is dirty or clogged it generally means someone has a low idle. Is your idle low, below 650 or so with the AC off? It could be but it would not explain your poor highway mileage. That sounds like incorrect fuel to air ratio and / or the timing being affected as well.
Just an example of what our LS's are capable of mileage wise. This was the average over 82 miles from a business trip today. Highway mileage of course. AC on, 93 degrees outside, cruise set to 75 mph and stereo on. It's very impressive. The car gets better mileage now then when I purchase it 3 years ago at 104k miles. Blows my mind. Especially when it is only rated at 16 / 23. I really do believe my mileage went up a few MPG after I replaced my temp sensor.
I agree MPG increases as more miles are racked up. My '01 (258K miles) with 5-speed tranny gets better MPG than the '06's with less than half the mileage. Lends credibility to the claim that the 3UZ-FE gets better with age.
I drive an 04 with 135k on it. My gas mileage is usually 18 or 19......can baby her to 20mpg hwy. Not sure if this helps at all...but when I start mine...during the warm up on high idle mine is not perfectly smooth.....she wiggles a little bit during warm up then once the idle comes down she is like butter. But the slight wiggles for me is possibly a hint that my girl wants something.....Im thinking plugs are a good place to start.....throttle body...air filter......
Even when I purchased my car at 104k, before all the tuning up I have done, I could get 25 or 26 mpg no problem. I don't know if there is something special about my car but not getting over 23 or 24 on the highway seems odd to me. I have no rough idle at any time. I would look into that. Also, some of that movement could be a sign the motor mounts need to be replaced. I plan on doing mine by the end of the year. O2 sensors play an absolutely vital role in engine effeciency. Both of mine have been replaced as well as the temp sensor as mentioned. This may be a key factor. If you are on original plugs at 135k miles you need to change those right away. The temp sensor also is very important. This sensor links right to the computer and has nothing to do with your temperature gauge. That is actually a different sensor. Multiple owners in my thread linked above have noted improvement after replacing this sensor. For the money I would do it. It's quite easy. Doing your PCV valve is also smart. I have a thread on here about that too. Don't forget to clean the MAF. Tire rolling resistance is another factor to consider.
[QUOTE=Lavrishevo;9088680]Just an example of what our LS's are capable of mileage wise. This was the average over 82 miles from a business trip today. Highway mileage of course. AC on, 93 degrees outside, cruise set to 75 mph and stereo on. It's very impressive. The car gets better mileage now then when I purchase it 3 years ago at 104k miles. Blows my mind. Especially when it is only rated at 16 / 23. I really do believe my mileage went up a few MPG after I replaced my temp sensor.
Radar Cruise is a great feature. Wish it came on my ML
When you say rough idle, how many rpms does it idle at when cold, how many when warm, how many when it's "rough"? Idle spec is 700-800rpm in neutral with the cooling fan and all accessories/AC off. If idle is too low, that could be a problem. Worn out engine mounts could exacerbate the problem.
When you cleaned your throttle body, did you get someone to push the accelerator to open the plate, or did you just push it open by hand? Pushing it open by hand is the incorrect way to handle electronically-controlled throttle plates, as it can throw off the calibration of the throttle position sensor, which throws off your idle speed and standard throttle open percentage. You can check your idle throttle open percentage using Techstream - spec is 14.4-16%.
Damaging the MAF sensor while cleaning is a common occurence I've read about on other car forums, which causes rough idle.
The other common causes of rough idle are: bad spark plugs, bad camshaft oil control valve (OCV should read 6.9-7.9Ohms at 20C, valve moves away from harness when battery voltage applied), incorrect valve clearance, leaking intake and/or exhaust valves, leaky cylinder, PCV hose leak or PCV valve stuck, intake manifold gasket leak, restricted engine air filter, faulty fuel pressure regulator, defective engine coolant temperature sensor, defective fuel injectors..
Plugs are a possibility I considered. But it's hard to fork out $75 on a set of oem plugs this early for a "possible" fix. AFAIK the plugs are supposed to be good for well over 100,000 miles. Another thing that deters me from this is the fact that there is no misfires. The temp sensor is another possibility. Although if I hook the code reader up before I start the car in the morning it says engine coolant temp is about 5-6 degrees from outside teperature. And after the vehicle is fully warm it holds steady at 195 degrees. Does this seem correct? Also I was not aware that there is an idle port on the throttle body. I thought the drive by wire throttle setups didn't have one. Although I cleaned it thoroughly i will admit it was hard to see. I just pulled the intake hose off and got in there with some throttle body cleaner on a clean shop rag. Where roughly would i find the port? I was lead to believe the techron concentrate was one the the best injector cleaners because of its PEA content. But I'm willing to try others if you guys have had better success with them.
FWIW I have had a rough idle in a different car that was caused by worn plugs. This was also before the recommended service mileage. Good luck.
06-24-15, 07:38 AM
05 ls430 rough idle
