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Mystery Misfire

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Hi guys,

My dads IS200 has a mystery misfire. The code is P0303 - Cylinder 3 misfire detected. Weve changed the coilpack twice and swapped it with that of another cylinder, and changed the spark plugs, but now were out of ideas. Its fine when its cold, but when it warms up it starts.

Local garage doesnt know what else to advise, so any ideas would be brilliant.

Thanks guys


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It could be some fluid in the spark plug hole.... also it is possible that the car needs a grounding kit as the original groundig points are corroded ( grounding kit costs about 40 pound on ebay)

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I had exactly the same symtoms on mine....fine on cold once warm terrible misfire. Gave it to an independant Toyota specialist who diagnosed dodgy injector. Replaced injector on cylinder 3 and cured it. Been sweet since (3 years). Not sure if you can get them tested on the cheap. Replacement was £110 for the part from Lexus.

Suppose you could swap the injectors to see if the fault moves from one cylinder to the other?

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Thanks for the replies, funny thing, I came on here to see if anyone had had problems with injectors as thats what had been suggested to us today. Were going to have another play tomorrow, although/ weve got some injector cleaner that hes gonna run for a tank and see what happens. Anywhere else to get an injector other than Lexus? Are used ones a bad idea?


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The IS200 injectors aren't shared with any other Lexus vehicle so you don't have the benefit of US suppliers or many aftermarket options. Used should be ok if you can get a low mileage one, you would just need to get replacement o-rings which are available from Lexus quite cheaply.

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