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Discussion Starter · #3 ·
Swap in a known good DENSO MAF. Most Toyota and Lexus use the same MAF.

That way you know quickly if yours is good or bad.
A new Denso MAF didn't solve my issue.
I have a hard start. Takes multiple key starts for engine to kick. When it kicks rpm is very low. I give it some gas to get around 1500 rpm and hold for several seconds. If I don't the car won't run well at all. Like the air/fuel mixture is corrupt.
Compression in engine is good 200psi
Fuel pressure going to injectors is good 45 psi
new MAF sensor
Would a logical step to look into fuel injectors? Using a stethoscope each injector is making tapping noise. Although, that doesn't prove if injector is clogged.
Codes I have are P0171, P0300, P0301, P0302, P0304
 

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What year, what engine, mileage?

What repairs were done on it recently?

Codes show engine is running lean and misfiring on all cylinders.

Unlikely that all 4 fuel injectors are bad at the same time.

Check air box and filter. Make sure clean and tight.

Check vacuum hoses from and to the throttle body for leaks and connected to the right ports.

Check 4 spark plugs. Make sure they are burning the correct fuel mixture with brown tips.

Could be fuel contamination.

O2 Sensor 1 controls fuel mixture. If it acts up it will cause lots of false codes.

Good luck
 

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Discussion Starter · #5 ·
2005, 338k. Air filter is clean. The butterfly valve isn't working, the vacuum hose underneath the air box was broken. Highly doubt it's that valve. I capped the broken hose coming from the engine.
I haven't seen any other broken hose. If there's a hole and pressure escaping I haven't noticed at the moment.

The O2 sensor was changed at 100k miles. I haven't thought that could be the issue. I had an error code that lead me to that issue. Car not throwing that error code now.
O2 sensor 1 is before the cat I'm assuming.


You mentioned make sure the throttle body has the hoses connected to the correct ports. What should be connected and where? If you could send an image. I say that because a mechanic looked at my car to look at my misfires. He just said the misfires happen on initial starts but then goes away. He never fixed it. And I was told the throttle body was cleaned. And as the outside weather started getting warmer my car has been giving me this hard initial start.
 

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All hoses from the airbox to the throttle body have to be connected and not leaking. If not engine will run rough at low RPMs.

The butterfly valve is supposed to close in a cold start for a rich mixture. Why is it not working?

Misfiring on all cylinders may be a problem with the ignition module inside the ECU.

You may want to spend $100 diagnostic fee for a Toyota dealer to troubleshoot the problems.
 
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