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Rx400h "check Engine" Hesitation Problem


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Our RX400h (delivered in November) is currently in the shop with a "check engine" problem. They've had it for a day now and are not yet sure what's wrong.

The "check engine" light came on a few days ago with no obvious drivability issues. Of course we checked the gas cap :) Called the local dealer and arranged for service and a loaner. During the drive yesterday to the dealer, the "check engine" light began blinking and the gas engine was stuttering and misfiring. Several technicians greeted us upon arrival and seemed eager to diagnose the problem. Talked to the Service Manager this afternoon and he said they think it's a fuel-related problem and that they were still working with the "experts" in California for a final diagnosis and repair.

Any ideas folks? I'll keep you posted when the dealer solves the problem. In the mean time we'll get by with a loaner RX330.

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It sounds like this condition is a "first" for most, if not all of us RX400h owners; we'll be interested in finding out the cause of the problem.

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The service techs certainly acted like it was a first for them, too! I just hope we don't have "lemon" :(

The good news is that I've never heard of a Lexus "lemon"! I'm sure your RX will be just fine.

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Latest update, Friday, Feb 10, Noon:

Service advisor tells me that it was an "engine misfire" diagnostic trouble code. Additionally he told me that they are currently leaning in the direction of fuel contaminarion, which restricts the injectors and causes check engine light and driveability concerns. They will be checking further Monday (today is Friday). If it's fuel contamination it very well maybe necessary to replace the injectors.

I would be surprised if it turns out to be fuel contamination because we only use name brand (76 Union) premium gas.

I'll keep you all posted.

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None of us would wish bad gas on anyone, however dont you remember in may of 2005 union 76 had contaminated gas at 300 washington gas stations. The Ferndale refinery added a contaminant and ruined the fuel injectors of hundreds of cars. I would at least check with your station to see if there was any other problem with this current batch of gas. just a suggestion

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None of us would wish bad gas on anyone, however dont you remember in may of 2005 union 76 had contaminated gas at 300 washington gas stations. The Ferndale refinery added a contaminant and ruined the fuel injectors of hundreds of cars. I would at least check with your station to see if there was any other problem with this current batch of gas. just a suggestion

I do remember that incident. One would hope that gas batch is long gone from the supply chain. I will certainly be asking that gas station about it if the Lexus tech truly thinks it was bad gas.

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Update 2/13/06:

Well, the Service Advisor called today and they're convinced the problem was indeed bad gas. His theory is that "suspended polymers" clogged the fuel injectors, although there was some disagreement with the "experts" in California who initially thought it was an electrical problem. So now they've ordered new fuel injectors and filters and will clean the tank and fuel pump. Hopefully we'll have our RX400h back by Friday this week.

My Service Advisor also told me that the RX fuel injectors are especially sensitive to fuel contamination problems .... something about the "unique design" of the RX injectors. Obviously this is a bit worrisome, especially when we've only bought name brand premium fuel. How does one prevent it from happening again? I wonder if using an additive like RedLine SI-1 Fuel Treatment regularly would help?

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Update 2/18/06:

Got our RX400h back today and it seems to be all better. They replaced all 6 fuel injectors, pulled and cleaned the fuel tank, and replaced the fuel filter. They still think it was a bad batch of gas. Our service advisor said that the RX engines have especially sensitive fuel injectors. He suggested adding a bottle of Redline SI1 or Techron fuel cleaner additive every 3 months or so to help keep them clean.

Here are the details from the work order of what they diagnosed and performed ....

Check engine light on, flashing then solid. Find codes P0300, P0304 & P0305. Misfires on cylinders. Clear codes and inspect data while engine under load. Noted misfires in excess of 50% at #5 cylinder only. Find misfire not always current. Find fuel trims well above normal. Also above normal for code stored data for "P0304". Contacted "TAS" for concern. Find no pending codes other than noted above. Perform misfire isolation diagnoses. Swapped ignition coils and spark plugs with #5 and #6 cylinders. Recheck for misfire. Find misfire still within #5 cylinder. Inspect fuel quality = unknown. Misfire caused from lean burn at #5 injector. Also pending codes P0300, P0302 & P0305. Perform A/F control active test. Set A/F to "+25%". Noted large improvement with no misfire felt. Remove & renew all fuel injectors. Remove fuel tank and renew filter/suction sock. Reinstall tank and check for leaks. Extensive drive test. No misfire noted. Recheck engine control and values are well within normal ranges. Clear codes and test drive second day with cold start. All good.

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Thanks for the report. I think it's a good idea for EVERYONE to add a can of concentrated Techron at least once per year. I'll be adding one to our RX, soon.

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