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2000 Es 300 Pops Back Thru Intake (backfire?)


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I have a 2000 Lexus ES300 with 110K miles that will pop or backfire up thru the intake.

Seems like it can happen one of two ways:

I am going slower, stamp on the gas pedal, lift, then stamp on it again. Pop.

Or, in traffic the other day, I was babying the gas waiting for the next lane to open.

I was on and off the gas lightly. The next lane opened, I stomped the pedal, and I got the pop.

It has only happened 2 or 3 times since I got the car in August.

Other than that, this is a great car.

Gas mileage is good, no other problems or symptoms.

Does anyone have a clue?

I have not looked at engine codes.

I saw something on that here yesterday. Need to take some time and try it.

Just thought I'd get the experts thinking about it.



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Backfiring is a taletail sign of running signifigantly lean. Check that there are no vacuum leaks, and that the entire fuel system is A-OK. Top to bottom. You will destroy the engine when it backfires if it runs to another cylinder & causes a massive detonation in that cylinder. It'll shove the piston down while it's coming up with no place to go. Shattering a piston, or snapping a rod, or wrist pin like a twig.

It's critical that you solve that.

You should also check the cam timing while you're at it.

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  • 2 weeks later...

Thanks for the response Toysrme.

I'm just getting back from a few days away.

The gas mileage cruising at 80-85 mph was approx 26.5 mpg.

Decent, so I don't think that it's running lean (from that perspective).

I will see what I can find for getting engine codes. This should be the best place to start.

Haven't figured out how or where to do that.

I can also start checking fuel system components, and possibly cam timing.

I don't want to ignore the problem, but if I behave myself, it doesn't happen.

...But I would like to eliminate it.


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That's good mileage. Running lean means you're running too little fuel.

You're running lean if you're backfiring. You *really* need to get ontop of that in a hurry before you're out alot of money. It'll be bad when you destroy a $500 MAF, A $150 IAC, or $300 worht of EGR valve equipment. Breaks off rubber hoses, or god forbid the detonation in another cylinder caused by the explotion in the intake manifold running down other open intake valves shatters a piston, or busts a rod.

Bad bad bad bad bad!

Not a condition you want to continue driving in indeffinately.

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I had the engine codes checked.

I got P0440 and 0441. The guy said it was gas cap/evaporative.

I left it running when I filled it with gas.

I will look around and check for hoses off or loose clamps, etc.

It doesn't idle high as I would think it would with a vacuum leak, but I will check.

You are also saying I should check all the fuel system components separately.

Let me see what I can do - that will take a little time.


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