Stft

RDWizard

Need help.
STFT erratic.
Cylinder 6 misfire detection.


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Quicksilvers

Since you say you have a misfire did you check the obvious electrical stuff yet coils, spark plugs etc.?

RDWizard

I got so frustrated I forgot the background. Heres the history. The problem started with P0011 code. Heres the list of things checked or replaced.

New spark plugs, swapped coils, new cvt solenoids, new cam pos sensors, new CVT Cam phase gears, new galley gasket, timing good, compression good, oil change, oil pressure good.

Something is affecting cyl 6 and Bank2 STFT.
O2 sensor looks good on Torque.
A/F Sensor looks to be ok.
Can't figure out why Bank2 STFT is erractic and Bank2 O2 is high but steady. Bank2 O2 sensor does move when revving so I know its working.

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RDWizard

Puzzled:

If STFT is High(+20%), that means that the A/F Sensor (Bank2_O2x1) is reading a lean condition and telling the ECU to add add Fuel?
According to my downstream O2 Sensor (Bank2_02x2) it is reading a rich condition while all this is happening. WTF???

RDWizard

I found this article to be extremely helpful in understanding what I have going on.
I definitely have an ignition issue!!

Using fuel trims and downstream O2s to analyze intermittent misfire concerns

Jhill

Interesting article, I’ve never done it that way but you may want to reread it. It states if your stft does not go over 15% then you are looking at ignition related, if it does go over 15% and into the 20’s then you have a fuel issue. Your data is showing 21.4%, also you have changed all plugs and swapped coils and misfire has stayed on cylinder 6. You have not done anything with injector testing ie injector balance test or scoped the injector voltage and amperage pattern vs other injectors (looking for pintle hump etc). Your stft 21.4% is trying to add fuel sensing a lean mis.

RDWizard

My ECU Cylinder 6 Ignition output is shorted. 19.9 ohms to ground. All the other cylinders are open. I pulled the connector at ECU to check for a harness short and nothing. Time to pull the ECU.

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Jhill

So this is a dead mid then and not intermittent I take it? I guess you just disproved his article then and would make sense why the misfire didn’t follow to another cylinder. Personally this is one reason I like using the HEI spark testers because they take the guess work out of if your car can make spark.