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Q: Why does the engine continuously backfire when accelerating ?
Idle is perfect on 2003 Lexus IS300

of Advanced Vehicle Technology‎
The idle is perfect but has no power when accelerating.
This car has had major parts exchanged to include the ECU, mainly because it had a piggy-back chip on the ECU. Injectors, plugs, MAF, throttle control motor, and the exhaust system with new cats have all been renewed. In the beginning before installing all new parts and the chip still in place, the car ran good !
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I hate changing any parts without proving for sure they are bad! It becomes very expensive. Has the oil been changed frequently, could have a variable cam issue or many other things hard to say without being able to do basic diagnoses tests. Start again with the basics.
There is a professional service called Identafix. They only deal with professional repair shops. They are in the Minnesota 651-633-8007 begin_of_the_skype_highlighting 651-633-8007 end_of_the_skype_highlighting. Your auto repair shop do all their diagnosis tests, and discuss your problem with a team of professional technicians great service cheap and very bright people. If the repair shop that are repairing your car are stumped this is a great service. This company only deal with automotive repair shops and don't answer questions for the general public but are an amazing knowledge base. A professional grade scan tool reads stored trouble codes, pending trouble codes, looks at live sensor data so you can look at a sensors performance and output signals without having to do intensive testing at each sensor, (cheaper scan tools have limited capabilities and may only read the trouble code stored). As with most things automotive it's best to check the basics first, check for vacuum leaks, fuel pressure and delivery volume. Verify engine mechanical integrity (even compression on all cylinders sufficient intake manifold vacuum at idle, ect....) before looking for complex problems check that the basics are sound.
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The parts were changed not because of trial & error but because they were found to be defective after analyzing and scanning. It's not that we haven't checked everything but apparently we're missing something and we haven't figured out what yet. We also checked all of the basics.

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