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Discussion Starter #1 (Edited)
Hey guys, thanks for taking the time to learn about my issue.

I have a 2004 Cadi CTS w/ a 3.6l engine. Recently, I have had issues with cylinder 6 misfires. It has been an intermittent problem over a couple months and now it is a constant issue. I have swapped out spark plugs twice, moved coil packs around, and have tested the cylinder for compression (it measured 180 psi) and am now stuck.

I'm in between guessing that it's an ECM issue or a fuel injector problem (the hours I've spent reading about issues that other CTS owners have led me to believe this, it could be completely wrong).

Could anyone tell me how I can test a fuel injector (possibly swap it for one in another cylinder) or anything else I might test? My guess is that I can't test an ECM. Could I take it to a shop that could test the ECM?

Any other suggestions are very welcome

Thanks to everyone who hopes to help!
 

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04 CTS 91 Aristo
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I'd suspect injectors.

I wouldn't suggest just swapping fuel injectors as a test because its still going to require the complete removal of the lower intake manifold and you don't want to be doing this twice. The passages where the injectors plug in are certainly full of dirt and require cleaning to prevent dirt from getting into the engine so you'll have to remove the LIM. You might also have carbon build-up on the backside of the valves and valve pockets. If you find that, which you will to some degree, you'll need to clean that too. The best way is to uninstall all 6 injectors and then send them off for cleaning and testing. Its $15-25 per injector for ultrasonic cleaning and flow testing so $90-150 total for all 6. New injectors would be closer to $50 a piece so this is still cheaper. While you're at it, I'd change the fuel filter. You can use CRC intake valve cleaner for the intake valves.
 

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Discussion Starter #3
Mandrake, thanks for the info

I changed the fuel filter last time I was under the car changing the oil filter housing gasket. I have the mileage written down somewhere, but I'm sure hoping that should still be fine

I'm really more interested in testing something to see if I can to narrow down the issue. The car has been running great until this misfire started popping up. I have time to dedicate to the troubleshooting process, an hour or two a day is fine and worth it if it helps me to locate the issue. I have looked and can also buy a new fuel injector for $30 (rockauto(dot)com); sorry if I can't do websites, just wanting to assist anyone else who might come across this thread.

Any other preferred method for testing the fuel injector in cylinder 6? I've tried to find information on working on these injectors but I haven't had any luck. Are there going to be timing issues or can I just plug one in and presto?

I'll have to look into the cleaner for the intake valves, I had thought about that after I found a video of a guy working on one of these engines and cleaning up under the intake manifold... https://youtu.be/7AEmOzKJP4c

Thank you again
 

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06 CTS Sport/Luxury package
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Three things made me cringe when I watched that video.

One, he did not put a clean paper towel in any of the intake ports. That's a must, especially since he was removing 10 year old tape from the harness right above those open ports.
Two, he used a shitty wire stripper. I can't believe those are still being made.
Three, used a low wattage soldering iron. Most definitely has cold solder joints on those wire connections.

Though I liked how he staggered the wires as not to make a bulge.
And I wonder at what point he disconnected the battery. Ha, didn't noticed that he did until he wiped the upper intake with the brake cleaner.

KOT
 

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iCadi you can test the resistance of each injector through the injection harness. There is a spec is the manual that they should be at. That'll tell you if the injector coil has a problem but it won't tell you if an injector is clogged or has mineral deposits affecting the spray pattern. You can pull the plugs and check the color. Other than that you have to remove the injectors.
 

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Discussion Starter #6
Thanks Mandrake, I've since figured the issue out. In short, it was a fuel injector on cylinder #6.

I purchased a new fuel injector and a set of gaskets to replace those on the upper intake manifold. I was beginning to see intermittent misfires on cylinder 2 before I started working on the vehicle but I didn't want to wait for another fuel injector to come in so I got started with a plan to diagnose that issue while there. I removed the upper intake manifold with help from this video: https://youtu.be/7AEmOzKJP4c

To diagnose the issue on cylinder 2, I swapped fuel injectors #2 and #1 and also moved the injector coil (formerly misnamed coil pack, by myself) to cylinder 5; I chose cylinder 5 because I didn't have to remove the upper intake manifold if this injector coil was bad. After resetting my check engine light and waiting for the misfire to occur, I discovered that the new issue followed the injector coil to cylinder 5. I order and replaced the injector coil in 5 minutes and have had no issues since.

I only state all this to help out anyone in need, as the information I could find readily available was hard to figure out and often had no final diagnosis (such as this).

All is well on this front, hope everyone has a merry Christmas and happy new year. Special thanks to this community for help with my issue and others.
 

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Hey guys, thanks for taking the time to learn about my issue.

I have a 2004 Cadi CTS w/ a 3.6l engine. Recently, I have had issues with cylinder 6 misfires. It has been an intermittent problem over a couple months and now it is a constant issue. I have swapped out spark plugs twice, moved coil packs around, and have tested the cylinder for compression (it measured 180 psi) and am now stuck.

I'm in between guessing that it's an ECM issue or a fuel injector problem (the hours I've spent reading about issues that other CTS owners have led me to believe this, it could be completely wrong).

Could anyone tell me how I can test a fuel injector (possibly swap it for one in another cylinder) or anything else I might test? My guess is that I can't test an ECM. Could I take it to a shop that could test the ECM?

Any other suggestions are very welcome

Thanks to everyone who hopes to help!
I have an 05 cts 3.6l .I have the same problem cylinder 6 .I swapped injectors with 4&6 put it back together same missfire.Then I replaced the whole injector harness.put it back together same problem.last thing to replace is the ecu module.it costs 359.I hope this works.
 

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I have an 05 cts 3.6l .I have the same problem cylinder 6 .I swapped injectors with 4&6 put it back together same missfire.Then I replaced the whole injector harness.put it back together same problem.last thing to replace is the ecu module.it costs 359.I hope this works.
Too Viper 73 did replace in the ecu work? In having the same issues
 

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Still waiting to get Ecu from flag ship.do not order from flagship.going on three weeks for them to ship it out from New York. I pretty sure the new ecu will fix the problem
Too Viper 73 did replace in the ecu work? In having the same issues
t From New York
 

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Still waiting to get Ecu from flag ship.do not order from flagship.going on three weeks for them to ship it out from New York. I pretty sure the new ecu will fix the problem
t From New York
Thank you for the input and the fast response. I'm driving mine right now was runnin perfect now started missing number 6 again. Open injector circuit number 6 and cylinder 6 misfire. I have replaced all the injectors injector connectors, spark plugs, fuel purge valve, new air Box and mass airflow sensor. I believe it's probably the eCU as well. After I replaced the mass air flow sensor and the crack air Box it ran fine then started missing again. Thanks for the tip to nothing worse than waiting on parts.
 

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Thank you for the input and the fast response. I'm driving mine right now was runnin perfect now started missing number 6 again. Open injector circuit number 6 and cylinder 6 misfire. I have replaced all the injectors injector connectors, spark plugs, fuel purge valve, new air Box and mass airflow sensor. I believe it's probably the eCU as well. After I replaced the mass air flow sensor and the crack air Box it ran fine then started missing again. Thanks for the tip to nothing worse than waiting on parts.
Looking forward to see how that you CU does for you
 

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Looking forward to see how that you CU does for you
Say I've been doing some reading while my car's missing still. One discussion said the Cam position sensors might be oiled up and not getting a good connection . So I pulled over and wiggled all of my cam position sensors and the wiring .hopped in my car fired right up its run in perfect now. Some of the wiring was oily. I'll let you know how this keeps up but still running fine 10 miles out now.
 

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I have an 05 cts 3.6l .I have the same problem cylinder 6 .I swapped injectors with 4&6 put it back together same missfire.Then I replaced the whole injector harness.put it back together same problem.last thing to replace is the ecu module.it costs 359.I hope this works.
I have an 05 cts 3.6l .I have the same problem cylinder 6 .I swapped injectors with 4&6 put it back together same missfire.Then I replaced the whole injector harness.put it back together same problem.last thing to replace is the ecu module.it costs
I have an 05 cts 3.6l .I have the same problem cylinder 6 .I swapped injectors with 4&6 put it back together same missfire.Then I replaced the whole injector harness.put it back together same problem.last thing to replace is the ecu module.it costs 359.I hope this works.
Try wiggling your Cam position sensor connectors. I pulled over wiggled all my oily connectors now runs fine. Can't believe it.
 

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That's awesome! BTW I always apply dielectric grease to all electrical connections when I remove them. I highly recommend that you do this to prevent issues in the future.
 

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Say I've been doing some reading while my car's missing still. One discussion said the Cam position sensors might be oiled up and not getting a good connection . So I pulled over and wiggled all of my cam position sensors and the wiring .hopped in my car fired right up its run in perfect now. Some of the wiring was oily. I'll let you know how this keeps up but still running fine 10 miles out now.if it was a cam wiring it would set a code for cam sensor or something related to a cam sensor.
 

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Too Viper 73 did replace in the ecu work? In having the same issues
Finally got Ecu.it fixed my misfire problems .there is a procedure to rest the computer . You. Have to turn the key to the on position for ten mins until the security light goes out then turn key off for 5 sec the back on for another ten min. You have to do this cycle 3 times then your car will start . It takes 30 min to do.
 

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Nice to know thanks for the follow up. I ordered cam position sensors i think this will fix mine. If not i know what i have to. Ecu!
 

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Finally got Ecu.it fixed my misfire problems .there is a procedure to rest the computer . You. Have to turn the key to the on position for ten mins until the security light goes out then turn key off for 5 sec the back on for another ten min. You have to do this cycle 3 times then your car will start . It takes 30 min to do.
I put in my new cam position sensors and still missing on number 6. Im ordering an ecu. Did yours come programed Or did you have to do anything besides they key rest?
 

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I put in my new cam position sensors and still missing on number 6. Im ordering an ecu. Did yours come programed Or did you have to do anything besides they key rest?
Mine came already programmed.I gave them my vin number. Removed the old Ecu.Then installed new Ecu . Then reset procedure.
 

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Mine came already programmed.I gave them my vin number. Removed the old Ecu.Then installed new Ecu . Then reset procedure.
Cool i ordered mine from Flashmasters on ebay today. Cost $367 total. It comes programed to my vin as well just need to do the key reset. I'll respond if it works for me or not. Thanks!!!
 
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