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Rx400H Engine Shudder Problem


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Hi all:

Last week, my 2008 Rx400h starting giving me trouble. Whenever i tried to start it (~90% of the time), the engine would "shudder" for ~10 seconds then idled out normally. It didn't do it every start-up, but did it more often when the engine was cold. I could also shorten the shudder duration by applying a little pressure to the gas pedal.

After a few days with no improvement, it started shuddering for longer periods of time. One day, i was at the drive-thru with the ignition "ON" and in D (engine off, as i wasn't moving) and as i pulled away, the engine started to shudder, and continued to shuddder as a was driving down the road. At that point, the check engine light came on and i dropped it off at my local mechanic.

They called the next day and told me me that i was having misfires; that two of the rear spark plug coils were bad. They changed out the three rear coils and all 6 of the spark plugs; so i had them do it. $750 incl. labor.

I picked up the car and it seemed to run fine; for a day. Then, the symptoms came back, but not as severe (and no check engine light). Dropped the car back off at the mechanic. Today they called and said that since the car isn't showing any codes, they're clueless. They "think" it has something to do with "fuel trim" (whatever that is), but without a code, they don't know. They want to keep it another day.

Any thoughts as to what might be going on? The shudder feels very similar to the feeling of the front wheels spinning when you floor it in an ES350 from a stand-still.

I've always used 93 octane from either Mobile or Shell.

I've noticed a loss in mpgs lately, down to about 19mpg vs what i used to get, around 21mpg.

I've also noticed a loss in power.

All fluid levels are normal; engine oil, coolant). No leaks from the engine nor inverter that i could find.

And i did the ISC reset when i installed a new battery a few months ago.

Any thoughts/ clarifying questions appreciated!

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Its a misfire, I have had the same issue. Mine was plug related although the code indicated coil. Since it was intermitant I went with plugs only and itr cured the issue .At 110K you should have all plugs replaced by now, codes from bad plugs can self clear after multiple starts. Coils can cause intermitant issues.

I did it myself, but a job not for the faint of heart.

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The plugs are normally replaced at 120k miles. However some have gone way over that mileage with no problems. The iridium plugs are very robust. I have to change my rear three soon, I obtained a manifold gasket and will attempt soon. My vehicle has 141k miles. The front plugs looked great at that mileage.

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Well, my mechanic thinks it's a bit more serious.

The check enging light came back on, but gave a different code than it did the first time; according to the mechanic, it's now giving them a "random" misfire indication (whatever that means). But they already replaced the bad coils and replaced all 6 plugs, and the problem is persisting.

They think there's a mechanical problem that's causing the code to come up as this "random" misfire.

They've localized the shudder's location to somewhere below the inverter, next to the engine (see sketch below)

2uoi3cy.jpg

They believe that it has something to do with the transmission and/or something hybrid related. This shop has little experience working with hybrids, so they suggested that i take the car to my Lexus dealer.

What stumps me is why the shudder occurs most often when the engine first kicks on when the car is in PARK.

I'm going to drop the car off to the dealer today. Any ideas as to what it might be?

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I wonder if the clutch between the engine and hybrid sytem is failing....I would have to review the theory of the Lexus hybrid to see it again. seems there was an electrical clutch.

The other thought since you have random misfires is that the oil control valve on either bank 1 or 2 is failing or the screen is dirty. On our old RX300's that happened with age and dirty oil.

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While I really like the idea of saving money by going to an independent shop, some "challenges" are best left to the dealerships. Even my 89 Mazda MX 6 GT is complicated enough so that I need an expert to troubleshoot certain issues.

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Thanks guys. I don't know how to diagnose any of those things... This car is too complicated! The car is with my local Lexus dealer now. They've been tinkering with it all day, and thus far can't figure out what's wrong.

All i'm seeing is $ signs... yikes

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I got a call this morning from the dealer. At 10am they still hadn't diagnosed it. They accused my prior mechanic of messing it up, and accused me of using bad gas (even though i have used 93 from shell or mobile exclusively). I cleared that up for them and they went back to work.

They called a few minutes ago.They believe coolant is seeping into cylinder #4, but couldn't tell me if the issue was a blown head gasket or a crack in the head. They said they won't know until they get it apart (how they made this diagnosis w/o taking it apart is beyond me).

They've already charged me for 2 hours labor to diagnose (even though they've had the car 3 days now), so i'm already out $240. They're now quoting me another $2500 (15 hours labor + parts) to fix the problem (assuming it's only the gasket) but advised me that it would be MUCH more if the head is cracked.

:censored:

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...just curious, but what is the ambient temperature range in your area? When you drive your RX, how far do you drive before entering the highway on cold mornings?

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...just curious, but what is the ambient temperature range in your area? When you drive your RX, how far do you drive before entering the highway on cold mornings?

In the winter, it gets into the teens, and in summer months can get into the high 80s/low 90s. My car is always garaged though (over night).

I live about 37 miles from work. The first 3 miles are residential and the remaining all highway. I've been making that cummute since September. Before that, i was going to college so i was driving ~7miles to and from school, twice a day for morning and evening classes. It's safe to say my 400h was abused...

And i can't say i was the type to let the car warm up before i'd be giving it full throttle. To be honest, i'd purposfully run it hard the first few minutes of driving to warm up the engine to get hot cabin air.

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...not the best conditions for engine gaskets, but still puzzling to some extent. I'm sure other owners have done the same under similar conditions. Your engine is virtually identical to those in so many RX models, after all.

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Sometimes I wonder if the constant off/on of the ice engine is harder on the engine than it being properly warmed up and maintaining temperature. Just the fact that it is being asked to turn off, turn on and doing this much more than the convention non hybrid does give me concern for stress on the engine components.

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However the Toyota prius has shown remarkable reliability in the taxi fleets nation wide. As for your oil useage I would suggest replacing your PVC valve. Also I hope you have been using full synthetic oil. Just strange for this particular RX400h. Will be interested to see what is the solution

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I've always replaced the oil and filter twice a year (Spring and Fall) with synthetic (Mobile 1), and always used 93 gas with either Mobile or Shell... at least since i've owned it since 2009 (it had 44,000 miles on it when i got it; all previous service intervals were completed at Lexus).

The only maintenance item that i didn't do was replacement of the transmission fluid. And i didn't get around to changing the spark plugs till now.

Dealer still has the car. I'll call later today to get an update.

I have my eye on another car in NJ that i'm thinking of trading-in the RX400h for.

Right now my Rx400h's inverter is leaking. Since my 400h is out of the hybrid warranty, if the inverter goes, i'm out an apparent $7,000. For the moment, i can just wipe off the pink "foam" (dried up fluid) and it won't come back for about a month. I want to get the car back and dump it quickly before more problems arise. It's turning into a money pit.

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yes penzoil titanium full synthetic, I will have them look at the pcv valve. Also for the issue on CD's vehicle. I just remembered my friends late model buick with 49K woke up one morning with this same problem. I have a trusted local mechanic and he said over the phone the GM coils were known to go out early, I think her v6 has three coils. He got the car and found ONE wire chewed by a critter in the wiring harness. Being honest he repaired that wire only forless than $100 instead of ordering a new harness and the car works perfectly.

CD do you think you have a chewed wire they have not looked for or found yet. Could that be the reason your problem came back, even after the first repair? what do you think

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katzjamr, i have no idea... I doubt it though, as it wouldn't cause coolant to be leak into an engine cylinder. I do however wonder how much of a coincidence it is that two coils would go bad at the same time as the head gasket. My guess is that my first mechanic simply diagnosed it incorrectly.

Lexus said the head gasket is bad and that the head is NOT cracked, so i'm happy for that. They promised that it'd be done tomorrow (Wednesday). Fingers crossed.

I'll be heading down (for me in RI, it's down) to New Jersey to make an offer on a '11 GS450h on Saturday.

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I got the 400h back yesterday ($2,740 later). Everything seems to be working fine now, no more shudder upon start-up. I did the ISC reset procedure, and reset my mpg calculator on the dash. I'm going to see if my mpgs go back to normal.

The sales person i've been communicating with for this '11 GS450h i was looking at in NJ isn't being cooperative. He's offering me s#!t for the trade and not budging on the price of the GS. Doesn't look like it's going to happen... Unless i invest $25,500.

I'm not a happy Lexus owner right now!

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Hey, you would be better selling your RX yourself, somewhat of a hassle, but I guarantee you would get a lot more. I did Craiglist, and made $3k more than the dealer offer. Just be careful, and cash only, even if it requires going to their bank. Sorry you had that streak of bad luck. things happen. good luck in your quest.

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Thanks lenore!

I ended up making a deal this weekend for that 2011 GS450h. Unfortunately i just don't have the time to sell it myself and deal with the hassle... I didn't get much, but at least it's gone. That car was a ticking time bomb!

I'll start a new thread in the GS450h area of the forum in a bit!

Thank you all for the help!

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Oh man I will now have to follow your projects on that car.

Oh yes, i'm sure there will be many projects! I just need the time.

The thread on the new GS is located:

http://us.lexusownersclub.com/forums/topic/80137-just-bought-a-2011-gs450h-traded-in-the-rx400h/

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