Plugs flooded with fuel
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Joined: Sep 2013
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From: Cape Coral, Florida
What DTC’s do you have so we can see how to approach your concern ??…if the O2 sensor is stuck low (below 450mv) the PCM will “think” the car is running lean and will schedule more fuel…I’d also check to see if you have spark on that one bank…may be a bad ground which grounds all 4 coil packs on that side.
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Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,633
Likes: 4,079
From: Cape Coral, Florida
Have the headers been installed recently and now you’re seeing these DTC’s ??…sometimes these long tube headers can affect how the upstream O2 sensors operate since they are further back in the exhaust stream vs the OEM manifolds…The DTC’s are for your downstream sensors which do not affect “fueling” which are handled by your upstream sensors…they (your 2 DTC’s) should have been “tuned out” if you no longer have cats…the P0300 random misfires can be caused by a rich mixture ( plugs fouled by excess fuel) as well as lean…was the one upstream O2 sensor changed or both ??…did you use OEM sensors or aftermarket ??…you really need a scan tool and a scope to see what’s going on with the O2 sensors, ignition system, the misfires, as well as fuel trims…since it is just one bank as you think it may be easier to diagnose…I’d find a diagnostic shop in your area or bring the car back to your tuner…what part of the country are you located ??…I may be able to suggest a shop.
Last edited by C5 Diag; Dec 6, 2021 at 08:37 AM.
