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2000 Avalon
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50 Posts
Discussion Starter #1 (Edited)
A friend's car. P0300, P0301 original issue. Checked coils, they had oil on the boots, and fouled plugs. I replaced the valve cover gasket. One coil was dead (cyl #1). I replaced it from one from NAPA. Codes were gone.

Then P0171 came up. I live streamed data and the MAF sensor was not operating correctly. Replaced MAF sensor. Code is gone.

P0300/P0301 keeps coming back, intermittently. Now you see it, now you don't. Injectors show correct resistance, and "click" when listening with a stethoscoppe. Smoked intake manifold, no leaks. Cylinder 1 plug is oil "wet" but not fouled. Other plugs are fine. Car has 168K on it. Next up is a compression check, but why this is intermittent is a puzzle. IAC valve is giving normal readings. I cleaned the throttle body and the owner had a shop do an injector cleaning and ran sea foam through the throttle body, but the code returns. Delete it, and it comes back in a week or two. Car seems to shudder slightly when cold and the AC is turned on. I live streamed AC idle circuit and it increases RPM when the AC turned on, as it should.

Any ideas on what to look at next? Thanks!
 

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Moderator
2006 Corolla XRS
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5,960 Posts
Use OEM coil pack. These are temperamental with aftermarket parts.
 

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Registered
2000 Avalon
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50 Posts
Discussion Starter #3 (Edited)
I installed the new one and it works. It was a NAPA branded part and wasn't cheap ($75). Strong spark jumps to a test ligbt. I put new NGK iridium plugs in too. I suppose I could get a denso coil and try that, but i don't see how replacing a part that works will solve the problem.
 

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2006 Corolla XRS
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5,960 Posts
Intermittent tells me it is sporadic behavior. No matter how expensive the aftermarket parts is, these engines are very sensitive to aftermarket parts.

Do you have the old coil pack?
 

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2000 Avalon
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50 Posts
Discussion Starter #5
No, that coil on plug was dead, dead, dead. I tossed it, and put a new one in. If I pull the new one, it sparks fine.
 

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2006 Corolla XRS
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5,960 Posts
Swap cop to see if cel follows to other cylinders. If it does, you found another dead one.
 
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