dmrinehart

I have a 2003 LS-430 with 125k miles. I feel occasional hesitation (missing) recently. It has happened 1) when stopped and starting to accelerate, 2) in the neighborhood at 25 mph when starting out in the morning, 3) cruise control at 70 mph in the morning. When cruising at 70 mph, I have felt this hesitation several times in a minute and then it goes away. It was happening before and now after spark plugs changed out.

ideas?

Tom57

If the hesitation is truly a misfire, and after new spark plugs, it may be an intermittent faulty ignition coil on one (or more) of the cylinders. The coil has one bolt holding it down onto the top of each spark plug. Have you checked for MIL codes with an ODD II reader?

It's also possible that it's a fuel injection issue. Have you ever run any fuel injector cleaner in the gas? Have you cleaned the throttle body?

Finally, it could be a VVTi oil control valve. (There are two on the 3UZ-FE.) This issue will throw a MIL code to help identify the specific problem and which valve is faulty.

dmrinehart

Thanks Tom for the suggestions.

1) I had fuel injection (throttle body cleaned) at 90,000 miles (35k ago). How often should thus be done?

2) I haven't used fuel injector cleaner. Any particular kind you recommend and how often?

2) I haven't looked at the codes (I usually have the shop do that). Sounds like that would be the next thing to do since some of these potential issues would be identified with these codes.

Thanks for your expertise in this area!

warminwisc

Maybe ya got some bad gas, did ya eat mexican? I digressed sorry run some "Heat" Isopropyl in it red bottle not yellow.

Daspyda

iTrader: (1)

A local auto parts store will usually pull codes for you for free.

Tom57

Warminwisc is correct, it could be simply a bad tank of gas.

Tom57

1) This is probably not the issue then.

2) There are threads on this topic with many passionate recommendations. I have used Techron. http://fuelinjectorcleaner.reviews/

3) If it's not a bad tank of gas, I'd have codes pulled (for free as suggested at auto parts store), then come back and report.

Bocatrip

. I may be wrong but if you do not get a visual warning which produces codes then resolving and finding the cause may be more difficult to find.

tallcaguy

Good suggests. How does an oil control valve cause an intermittent misfire? Wouldn't it be more frequent or even continuous?

tallcaguy

Sorry I meant intermittent hesitation (not misfire).

Tom57

It's the 3rd of 3 ideas offered based upon the OP's description of the symptom. I read the word "misfire" to mean a hesitation on one or more cylinders not caused literally by failure of gas to ignite.

The OCV's are integral to the proper operation of the VVTi (variable valve timing with intelligence) on each bank of 4 cylinders. Each OCV manages both the intake and exhaust cam timing on the bank of cylinders, through the full range of RPMs and load. The valve has an electronic solenoid which in turn is managed by the engine ECU. The OCV electronic solenoid can fail intermittently, and the valve can stick intermittently, at different RPMs and loads. If one OCV is failing, that bank of cylinders won't be in sync (proper advanced timing) with the other side bank of cylinders. The engine will stumble. (May feel like a "misfire.") It can happen in idle, or at higher speeds.

Bocatrip

Since you do not have a misfire but occasional hesitation you most likely are experiencing a "drive by wire" issue. There is a long thread I originated which I believe is titled intermittent hesitation upon acceleration. I have never been able to resolve mine and have learned to live with it. Sorry I don't remember the title of the thread. If I remember the exact name I'll chime back in. There are numerous parts in the "drive by wire system" and I was not going to guess in order to replace parts. Good luck.

Bocatrip

As I responded earlier, I have been experiencing hesitation upon acceleration pretty much since I purchased my car 6 years ago. It had always been somewhat sporadic and infrequent. I investigated the problem a few times at Lexus with no luck. Currently, it has reared it's ugly head fairly regularly. It it continues, I truthfully do not no where to turn. No codes show up, and previous visits to Lexus show nada. No posts here have shown any conclusive fix for this issue which has plagued a number of owners. Will this be the last straw for me? I sure hope not, but nothing is forever especially if it involves a nagging persisting problem that affects performance as well as safety.

Tom57

What components have you either replaced, or eliminated as not being the cause of the problem? Have you considered replacing the throttle position sensor?

Edit: It could be one faulty spark plug or plug wire. This could be detected though on an engine analyzer, but only if the symptom was occurring when tested.

Bocatrip

My car does not have a miss or "miss fire"... It is running on all 8 cylinders. I have had the maf (mass air flow sensor) cleaned. I had the shop foreman take a ride with me with his lab top hooked into my car's diagnostics for 30 minutes. Nothing showed up at that time, but the car did perform fine at as well at that time. Now, it hasn't many times over. Not sure having him with me would have helped. I was told that unless any of the many parts of "drive by wire" fail completely...it will not show a fault...thus the problem here. Not going to throw money into parts to see if it works. Too old a car.