Bad cat? O2 Waveform

2010 Dodge Charger 5.7 hemi (lean misfire bank 1) I suspected bad downstream O2 sensor fixed rich would not respond to my huge vacuum leak I would create Frame 3400

So I changed bank one downstream sensor , The misfire only occurs when going into closed loop now I am suspecting a bad cat I do hear a rattle

Vacuum leak creative here at frame 1400 I do notice the downstream seems to mimic the upstream


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Did you happen to capture the fuel trims AND O2's during the misfire? What were the original trouble codes?

(null)
Original codes
P2314 ignition coil 5 secondary circuit insufficient ionization

P0305
Cylinder five misfire

#5 Coil pack + injector looks Great on the scope
Plugs good,

Relative compression test sounds inconsistent sometimes and then it sound normal

Fuel trims go -18 then go back to normal fluctuationing while missing




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As soon as system goes to closed loop , misfire occurs and short trip drops way negative


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Columbus450 wrote: Fuel trims go -18 then go back to normal fluctuationing while missing

When does it go to -18% In open loop? Both banks?

Does Mode $06 agree with the P0305?

#5 Coil pack + injector looks Great on the scope

Really? The coil pack looking good is surprising, given the P2314. Is the burn time on #5 similar to a known good cylinder?

A scope relative compression test is probably a good idea at this point. You can use a good ol' set of test leads if an amp clamp isn't available.

(null)
-18 when in closed loop looks like both banks

I know right I swapped with good known coil
pack no change




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The misfire only occurs when it goes in closed loop in open loop it’s good, which is why I’m focused on cat and o2 sensors

The moment it goes in Closed loop short term goes way negative


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If you are able to do a WOT(Wide Open Throttle) test,

You want to see;

Rich 02's
High Calc. Load
High Map Pressure.

If the Calc. Load is Low but the others are good, then you have a breathing problem ie. restricted exhaust/valve timing.

not sure why you're looking at the down stream 02 and the CAT at this point. look at the up streams for data.

the secondary circuit on the coil is the ignition boot, spark plug boot or spark plug wire. check to see that all is ok and you have a good high energy ignition spark at the plug. as moderator said, can be wiring problems at coil. you swapped the coil pack but no mention of the other (plug wire, or boots, plug)

fuel trims are going to be off at this time due to the misfire. if 02 are going rich and lean then they appear to be working at this time. -18 would not be out of line for a misfire, pcm is taking away fuel.

(null)
Scanner John,I did swap coil packs and spark plugs , this design the rubber boot is connected to the coil pack so that got swapped as well the misfire still remains on cylinder #5 I believe I have a compression issue on that cylinder I believe I have a compression issue on that cylinder . Even if it is a compression issue I don’t know why the car would be throwing codes for the coil pack ,I also did a current ramp test with my scope and everything looked great looks consistent with the other cylinders on the same bank


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that's the trick of things... just because you get a code, it does not necessarily mean the coded part is the problem. Paul Danner is a master at automotive diagnosis. He reads and interprets data then test and confirms before making a repair.

That coil pack may be good, but a signal being returned to the PCM could be what is setting the code. A short to ground is a killer sometimes. You have tested the part you also have to check the wiring harness.

Negative trims is a rich condition... the PCM is taking away fuel. Mis-fire will occur if too much fuel is in a cylinder drowning out the plug. High positive(+10 or more) trims that get better with higher RPM are indicative of a vacuum leak. If you have high negative (-10 or more) LTFT and STFT going the same way I'd look at a fuel delivery problem.

Use your upstream (B1S1 and B2S1) 02 data not downstream at this time. Problems with the fuel pump, fuel regulator, EGR, EVAP and fuel injectors are just a few associated with high negative trims.

Found the prob scope wasn’t very helpful on this one, Pulled-valve cover
Cylinder number five- intake valve has 0 cam lift , Camshaft lobe is wiped out due to failed roller lifter


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