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Discussion Starter #1 (Edited)
Looking for some help and info. I recently changed Spark Plugs and Coils in my 2009 G8 3.6L and when I tried to start it after finishing up it had a terrible misfire and threw multiple codes. Plugged in my reader and it had P0300, P0301, P0303, and P0305. Misfires on all ODD cylinders. I’ve checked the grounds, replaced the intake gasket, replaced the Camshaft Position Sensor and the Camshaft Actuator Solenoid. And still throwing the same codes. It starts, but has an Extremely rough idle. I made sure the all the wire connections were good and even check my MAF sensor voltage. If I give a little gas and hold it around 2000 RPM it seems to smooth out but when letting out of gas it acts like it wants to die. The plugs were gapped to .040 ACDelco, and the Coil Packs are Denso I do believe. I’m stuck on ideas and at a stand still on ideas. Any suggestions?
 

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We are T/S the passenger side of the engine, correct (cylinders 1-3-5 are on that side on this engine). Wouldn't think that the fuse could have blown, but checking is easy. That fuse powers up all 3 ODD coils an injectors. Its fuse F35-20A located in the underhood fuse box. The 1-3-5 coils have their ground wires spliced together in the harness and the takeaway ground wire is attached to a point just above the #1 cylinder exhaust port (at least that's what the service manual says).
 

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No it was not running like this before. I drove it to and from work that day. (100 mile round trip) and I checked fuses. I did not know where the coil grounds were thank you for that info. I’m just not understanding how a (what I thought was simple) spark plug change turned into a pretty large chunk of $$$
 

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We are T/S the passenger side of the engine, correct (cylinders 1-3-5 are on that side on this engine). Wouldn't think that the fuse could have blown, but checking is easy. That fuse powers up all 3 ODD coils an injectors. Its fuse F35-20A located in the underhood fuse box. The 1-3-5 coils have their ground wires spliced together in the harness and the takeaway ground wire is attached to a point just above the #1 cylinder exhaust port (at least that's what the service manual says).
I changed the Plugs originally and after is when problem first came up. With original coils, so that’s when I replaced the coils, and the Intake Gasket. Put everything back together and it was still happening so that’s when I changed the Camshaft sensor and actuator solenoid. Problem was still there. I’m wondering I may have cut a wire in the coil pack harness but idk how to test that. I’ve read a bent valve can cause others to bend also. And G8 are common for valve spring issues but why so all of a sudden. I drove the car to and from work no issues, 100mile round trip. But after plugs changed it was acting possessed. Plugs were gapped at .044 which is what it calls for I believe
 

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If you can get a hold of a multimeter, you can T/S this a whole lot. With the ignition key moved to the #2 position (power full on but not running), pin D (PK/D-BU wire) of each coil connector must read 12 volts DC when the other lead is connected to a known good ground source. Do a little wiggle checking to make sure the voltage remains steady. IF OK turn off the ignition an move on to the next item. Pin A (BK wire) from each coil connector must read continuity to a known good ground source (that's the ground wire that ends being grounded at the cylinder head). Pin B (Purple wire) must also read continuity to a good ground source. That wire (from each coil) is spliced together (at an appropriate location) an that wire continues back to a ground source within the ECM. Wiggling/flexing the wire harness for each wire checked would help to locate or verify if any breakdown of the wiring has taken place. Pin C is the triggering signal from the ECM to make the coil discharge its energy to the spark plug when commanded.
 

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All things being equal, find it difficult to imagine there being anything wrong with either the spark plugs or ignition coils installed since each group was from the same manufacturer. Would be more plausible if they were used takeoffs, but am assuming they were brand new. The likelihood of there being a defect in the ignition coils or spark plugs relegated to one side of the engine is very slim. By the way, the 3.6L G8 V6 has four camshaft position solenoids and four variable valve timing actuators. Which of the eight were replaced? Fuse F35 in the engine compartment fuse block powers the odd ignition coils and presume checked the fuse translates to test each side for continuity. Do you have the part numbers for any of the installaed compoments?
 

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Discussion Starter #9
All things being equal, find it difficult to imagine there being anything wrong with either the spark plugs or ignition coils installed since each group was from the same manufacturer. Would be more plausible if they were used takeoffs, but am assuming they were brand new. The likelihood of there being a defect in the ignition coils or spark plugs relegated to one side of the engine is very slim. By the way, the 3.6L G8 V6 has four camshaft position solenoids and four variable valve timing actuators. Which of the eight were replaced? Fuse F35 in the engine compartment fuse block powers the odd ignition coils and presume checked the fuse translates to test each side for continuity. Do you have the part numbers for any of the installaed compoments?
Yes all components were brand new. Solenoid Part Number: TS1013
Cam Position Sensor: SU9680
Spark Plugs: ACDelco 41-990
Coils packs: Duralast C1555-6

The old Plugs that cam out were Gapped at .06 so last night I pulled all 6 of the new ones back out (all 6 were coated in Black like the were fouled) and matched gaps and it didn’t seem to change anything. Put brand new ACDelcos in (came pre-Gaped .044) I’m leaning more towards an electrical issue in the harness. Or internal engine. I didn’t bring my Fluke (Multimeter) home from work yesterday so I couldn’t test Circuits. That’s next on my list. For the first 15-30 sec after starting it seems to run fine but after the Systems Check finishes it starts to act up. I wouldn’t think the ECM went bad but at this point.... anything is seeming like the issue. Parts cost isn’t an issue I’m just trying to t/s this prior to having a Shop take over cause Labor cost is outrageous.
 

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Discussion Starter #10
If I take car to Shop it would only be because they have more available resources than I I have in my Garage.
 

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What is the vehicle's current mileage? In the past, had mixed results with Auto Zone parts and typically order parts online time permitting. Am fully aware many parts are simply repackaged by various manufactures, but still prefer the part to be marked made by xyz manufacturer and/or their packaging. In this case, sub-standard parts are not the problem given the troubleshooting steps taken thus far. Be that as it may, a little fouling on the first set of new spark plugs is normal doe to the engine misfiring. Don't own (should) a multi-meter and instead use a continuity tester to ensure the harness is getting ground and voltage. Not nearly as accurate as a multi-meter, but it does give some insight as to what the culprit might be.
 

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Discussion Starter #12
What is the vehicle's current mileage? In the past, had mixed results with Auto Zone parts and typically order parts online time permitting. Am fully aware many parts are simply repackaged by various manufactures, but still prefer the part to be marked made by xyz manufacturer and/or their packaging. In this case, sub-standard parts are not the problem given the troubleshooting steps taken thus far. Be that as it may, a little fouling on the first set of new spark plugs is normal doe to the engine misfiring. Don't own (should) a multi-meter and instead use a continuity tester to ensure the harness is getting ground and voltage. Not nearly as accurate as a multi-meter, but it does give some insight as to what the culprit might be.
A multimeter I do own (Fluke), just use it at work more than I do home. I forgot to grab it yesterday when locking up the my toolbox
 

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I* don't own (should) a multi-meter...
 

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Very well. Don't think replacing the other camshaft position solenoid nor variable valve timing actuator will solve the problem since each have codes that should illuminate the check engine light indicating a malfunction or failure.
 

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Discussion Starter #17 (Edited)
!!!!!!UPDATE!!!!!!

I’ve tested coil connections with multimeter and all things normal with that. Other than I’m not sure how to test the ECM signal wire on the connector. I’ve gotten It in the air and looked at bottom side for obvious issues, did find what seems to be a vacuum line/plug with hose that wasn’t connected to anything, found additional plug around same location with a T fitting on end of hose not connected to anything. Gonna go out on a limb that there should be a 3rd hose that goes to the T fitting if they are to be connected. I’ve read on forums with the same 3.6L LY7 issues and they mentioned a bad connection in the X3 connector on bottom side of fuse box (engine compartment) Pin 51 is for Odd coils/Injectors and Pin 54 for Even coils/injectors. Aside from that I’ve also read (not sure of possibility) that dealerships have had same Issues come in and the things they replaced that I haven’t already are: 1. Timing Chain 2. Catalytic Converter on misfire bank exhaust, and 3. Electronic Brake/Traction control Module.
 

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Engines that still have leads going from a coil to the plug would/could allow you to verify if any plug was receiving a constant rhythmic spark using the old timing light gun. I wonder if an inline spark tester would work with engines that are the direct coil to plug version. I have one of those for testing 2 an 4 stroke engines. It would attach from the coils plug receptacle (on one end) an the other end would be plugged onto the plug. The device has a view thru window that allows you to see if its sparking. If everything was working correctly prior to replacing all of the components you did, it sure sounds like the problem has to be in that area where your hands were working.


You do know that the power supplied to that bank of coils, also powers up the injectors on that bank. Any fuel injector(s) having a problem can also cause the system to display a miss-fire condition.
 

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Discussion Starter #19
Engines that still have leads going from a coil to the plug would/could allow you to verify if any plug was receiving a constant rhythmic spark using the old timing light gun. I wonder if an inline spark tester would work with engines that are the direct coil to plug version. I have one of those for testing 2 an 4 stroke engines. It would attach from the coils plug receptacle (on one end) an the other end would be plugged onto the plug. The device has a view thru window that allows you to see if its sparking. If everything was working correctly prior to replacing all of the components you did, it sure sounds like the problem has to be in that area where your has were working.


You do know that the power supplied to that bank of coils, also powers up the injectors on that bank. Any fuel injector(s) having a problem can also cause the system to display a miss-fire condition.
Injectors I did read are one of the first things the dealer will replace? 10 days before replacing Spark Plugs, started my car up to leave at lunch and it felt hesitate and dogish, Started to pull out of the parking lot and it through a code. I hooked up my reader when getting back to work and it threw a cylinder 3 and 6 misfire. But didn’t seem to happen again. After work. That was on the 19th, now the codes and the description from the print out said that the code should clear itself if the problem doesn’t occurred for 60-80 miles of normal city driving. My commute to and from work is 100 miles (round trip) well Saturday Morning (23rd) CEL still on so after work I went to the part store (CEL still on) buy the spark plugs and when I started the car after coming out of parts store CEL was off, so I held off on changing the spark plugs and kept an on the cars performance, Monday I had some time to take advantage of the already bought spark plugs so I changed them. And when first trying to start it it didn’t start at first, on the second try it started but didn’t stay running, third time once it started I gave it a little gas and right afterwards, that’s when the 1, 3, and 5 cylinder misfire came up, and the cars idle was very rough and shook the car, wants to die if throttle isn’t feathered to bring it out of the low rpm idle. If I keep it running by giving it gas and keeping it around 1800-2200rpms the CEL starts to flash and ding, and after about 30 seconds of that it goes to limp mode, “Safety Mode Active/Power Reduced” could it be a shot catalytic converter from the initial attempts of starting after the plug change?! Seems possible if that was the cause of the codes on the 19th.
 
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