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Old 12-16-14, 12:59 PM
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IS250 Engine misfire-explained

 
Old 06-01-12, 10:42 PM
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solotex55
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Default IS250 Engine misfire-explained

Hi guys and gals, I am a Lexus Senior Certified tech at a large Lexus dealership. In reading some of the posts here, I see alot of confusion about this subject. You seem to know about carbon build-up, but not the how or why and most important...the fix or prevention.
First, how and why...the misfire is caused when carbon that has built-up on the intake valve flakes off and becomes stuck between the valve and the seat causing loss of compression. This can last from a few seconds to minutes. It does not damage the engine, but can set a Check Engine light if it lasts long enough. The carbon is caused by crankcase blow-by...oil getting in the intake system. With a Direct Injection engine there is no fuel flow over the valve to clean it. The fix is to reduce blow-by...after you clean-up the valves. Lexus has another TSIB out for this. I believe it is L-SB-0048-11. It involes replacing ALL the pistons and rings,also cleaning the valves and replacing the valve stem seals. I personally have done 4 of these. It is most common around 60k miles, but have seen it as low as 29k. It is fully covered under 6/70 powertrain warranty. Now about prevention....I don't know of any. Why do some cars do it at 30k and others have 100k w/o a problem??? Synthetic oil may help, but not enough data to be sure. Good, clean oil can't hurt. The 350 and V-8 models do not have this problem. If you have any questions I will try to answer them as best I can.
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Old 06-01-12, 10:48 PM
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I got the TSIB number wrong...it is L-SB-0068-11
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Old 06-01-12, 11:26 PM
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Does the 2011-2012 is250 have or will have these issues?
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Old 06-01-12, 11:42 PM
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KillaIS250
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i think most people know of this stuff cuz of the giant Carbon Build up thread
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Old 06-02-12, 12:07 AM
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Originally Posted by KillaIS250 View Post
i think most people know of this stuff cuz of the giant Carbon Build up thread
I was gunna say the same thing... its been beaten into the ground over and over.
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Old 06-02-12, 12:28 AM
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So, does an oil catch can help??
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Old 06-02-12, 06:29 AM
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ok in your expertise what should I do, my car does the start up grinding noise but only occasionally, but its definitely present. I am 6 month or 6,000 miles away from being out of power train warranty, they had my car for 5 days but miraculously couldnt reproduce sound **cough** ... any advicE?
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Old 06-02-12, 09:58 AM
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Originally Posted by Vroomin350 View Post
ok in your expertise what should I do, my car does the start up grinding noise but only occasionally, but its definitely present. I am 6 month or 6,000 miles away from being out of power train warranty, they had my car for 5 days but miraculously couldnt reproduce sound **cough** ... any advicE?
Several members have used their cell phones to record sound/video of every start up of their car until it happens, then used said video to convince the dealer to fix it per the TSIB for the cam gear rattle.
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Old 06-02-12, 01:10 PM
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When is Lexus going to make a D4-S injection system on the IS250 engine....like the injection system on the IS350 engine...that would definitely solve this problem!!!
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Old 06-02-12, 04:55 PM
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solotex55
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I know there is alot of talk about the carbon issue on here, but didn't see anything about the newest TSIB. So, use this info for what it's worth to you.
As far as the 2011-2012 models, they have the updated rings. We have not seem any problems yet, but most are at low miles.
On the noise issue..recording it is a great idea.
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Old 06-02-12, 05:05 PM
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yoan hit me up i got the hook up at the dealer
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Old 06-02-12, 05:15 PM
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solotex55,

You mean this lastest TSB. I had posted a while back in the merged carbon build up thread.

Originally Posted by Sango View Post
Managed to get the PDF!! Enjoy!

Last edited by Sango; 06-02-12 at 05:18 PM.
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Old 06-02-12, 09:13 PM
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Mine started doing it at 16k miles. Now at 23k, it's happening more. My dealer has it now, trying to reproduce it (they aren't feeling it and there are no codes). I admit, I mostly drive city and rarely ever punch it. There's a part of me who feels bad I've accelerated this problem via my driving habits. Still doesn't make this problem excusable though.

What makes me nervous is having so much of the motor taken apart and redone. It can't be good for resale value, if one keeps records and the new buyer asks to see. Also, this all gets logged into your car's database at dealers. It's going to be available for a buying dealer to see too. And you know that one sneaky salesperson trying to edge out a few hundred bucks in a trade in is going to bring this up for leverage.

For this particular situation, I am disappointed with Lexus. I think a goodwhill gesture would be appropriate to ease tension.
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Old 06-03-12, 12:21 AM
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i just dropped my car off to the nearest lexus dealer(128 miles away) and had the same tsib you stated(0068-11), it felt like my engine blew up, many people told me it was my coil packs which is not covered under lexus warranty.. so I actually hope my engine needs rebuilt!!! if not a lot of money is coming out of my pocket ((
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Old 06-03-12, 12:59 PM
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First off, I'm not having any problems with my '08 250, 40,000 miles...yet. I was concerned enough to contemplate an oil catch can but after examining the PCV valve and found it to be completely dry, I abandoned the idea, as with any blowby, I should have seen at least an oil sheen. I have heard the problem could be caused by the EGR valve depositing unburnt hydrocarbons on the valves lubricated surfaces at high temps. As I rarely drive under conditions (such as highway with minimum to moderate load at higher rpms), where the EGR is in play I'm wondering if this is why I've been fortunate. M y driving is open urban roads with 45 mph speed limits and very few stop signs. I also use Mobil 1 as my choice for oil.

It's obvious that with direct injection there's no cleaning of the intake valves with gas. So, besides reversion due to cam timing, if you don't have ring leakage and horrible blowby, where are the deposits coming from? Could it be EGR? If so, wouldn't it be simpler to duct cleaner exhaust gas from after the cat to the intake manifold rather than from the exhaust manifold itself? Sure would be worth a try rather than replacing pistons and rings in an otherwise healthy engine.

One question for you that's a little off topic: There is what I believe a secondary set of throttle butterflies in the intake manifold, most likely short and long runners for better torque at different rpms??? Could you explain how they're controlled and what they accomplish?

Thanks
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