Misfire P0430 and P0420
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Cadillac SRX First Generation Forum - 2004 - 2009 Discussion, Misfire P0430 and P0420 in Cadillac SRX Forums; I have a 2006 SRX V8 and my codes are P0300, P0308, P0430 and P0420. The first two codes point ...
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    st8w8 is offline Cadillac Owners Member
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    Misfire P0430 and P0420

    I have a 2006 SRX V8 and my codes are P0300, P0308, P0430 and P0420. The first two codes point to a random misfire and a misfire on cylinder 8. I've changed all the spark plugs and the coil for cylinder 8 but the problem still persists. the car is idling really rough and sluggish upon accelerating and i can smell alot of exhaust. Was wondering if both cats are bad and would replacing them solve my problem. or is there something else wrong.

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    glake89's Avatar
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    Re: Misfire P0430 and P0420

    Often overlooked on misfire codes is the injector which I suspect is your problem, especially since you have the 420 and 430 codes. The fact that you have both 04xx codes leads me to think some injectors on the other bank are also weak. That's where I'd look.
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    Re: Misfire P0430 and P0420

    Have you ever had your Timing Chain replaced?

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    st8w8 is offline Cadillac Owners Member
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    Re: Misfire P0430 and P0420

    No timing chains ever replaced. Just got it a month ago. How would I know if the injectors are bad.

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    Re: Misfire P0430 and P0420

    You can test the solenoids on the injectors yourself if you're handy and have a DMM. Flow testing or clogged is a bit more difficult but can be done if you're real handy. I suspect it's fairly high miles. You might try double dosing (cans/tankful) of a good cleaner such as Techron for 2 or 3 tanks.
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    st8w8 is offline Cadillac Owners Member
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    Re: Misfire P0430 and P0420

    I've used techron twice in the past week. Going to change fuel filter and check the injectors later on today.

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    Re: Misfire P0430 and P0420

    If the ECT sensor reads between 50-90 degrees, look for 11-14 ohms across injector pins.
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    st8w8 is offline Cadillac Owners Member
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    Re: Misfire P0430 and P0420

    Injectors are fine according to a local shop. They insist that the cats are in need of replacing

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    I also unplugged each coil one at a time noting a difference in idle but no change when I did the #8. After the codes were cleared problem went away but an hour later rough idling and acting sluggish again

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    Re: Misfire P0430 and P0420

    The misfire may have damaged the cat, true. Check with customer service on this site for extended warranty on some cats, or your dealer. I seem to recall that there is some design problem in the N* that affects cyl.8. Maybe someone who knows will chime in. Interesting that erasing the code relieves the problem temporarily.
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    st8w8 is offline Cadillac Owners Member
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    Now getting misfire on 6 and 8. Wtf.

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    Re: Misfire P0430 and P0420

    Try disconnecting and re-connecting #2 connector on the ECM. There are 3 connectors, 1 &3 are 56 pin and #2 is 73 pin and black color. Injectors and coils both are in #2 and I suspect some pins are not making good contact.
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    st8w8 is offline Cadillac Owners Member
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    An update on my situation. Got the driver side catalytic converter replaced. Passenger side was fine. Also replaced all o2 sensors a total of 4. And still getting misfire on cylinder 6 and 8. The p0420 and p0430 codes are gone. Also misfire gets worse with the ac on.

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    Re: Misfire P0430 and P0420

    Is the MIL flashing or on steady? Are your only DTCs 300, 306 & 308?
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    st8w8 is offline Cadillac Owners Member
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    Only codes are 306 and 308. Mil stays on and only flashes upon hard acceleration.

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    Re: Misfire P0430 and P0420

    Here's my reading of your situation. The MIL flashes if the miss will likely cause converter damage; to me that means unburned fuel due to plug or coil being bad (not firing). Otherwise the CK sensor is detecting a slight discrepancy in crankshaft rotation. I suppose this could be caused by some unbalance condition but I lean toward not enough fuel in those 2 cylinders. If it were an electrical problem the would probably be separate DTCs for that. Sounds to me like physically pluggedor dirty injectors, or else something like coolant leaking in or out of them. Might be time for a compression and leak-down test. When your mechanic said the injectors were ok, did he remove them and do flow and spray pattern tests?
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