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Discussion Starter #1 (Edited)
Hey guys, had a no start condition, changed all the plugs and coils. Cars running fine now except i'm getting a rough idle, I decided to start pulling coils to see which one of them was misfiring because I had a feeling that was my problem. All of them are good except #1. After unplugging the #1 coil, my engine doesn't change at all. With there being a new coil and plug in there, i'm thinking the problem might be with the wires/connector. Anything I can do to verify that its the wiring? And if it is the wiring, how can I get this fixed?

This is how the engine sounds if it helps.
 

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2004 chevy trailblazer_lt
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First, have you scanned for OBDII codes? If yes, then what are they? Second, go back and make sure that the coil is securely seated on the # 1 spark plug. Third, if the engine is still missing, then you will need a electrical diagram that gives the pinout of the ignition coil electrical connectors. A Haynes manual should have such a diagram along with wire colors.
 

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Discussion Starter #3
First, have you scanned for OBDII codes? If yes, then what are they? Second, go back and make sure that the coil is securely seated on the # 1 spark plug. Third, if the engine is still missing, then you will need a electrical diagram that gives the pinout of the ignition coil electrical connectors. A Haynes manual should have such a diagram along with wire colors.
Yes, the scanner gave me p0300 random/multiple misfires, p1345 cam to crank correlation fault, p0141 o2 sensor heater circuit bank 1 sensor 2. I've checked the #1 cylinder with 2 different coils, making sure that I put them in right. And what am I to do with the pinout? Any electrical work that has to be done would be tasked to someone else as I lack the knowledge.
 

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2004 isuzu ascender
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You might have a problem with either the camshaft position sensor or the crankshaft position sensor. These are used to adjust the variable valve timing, so if they’re not working it’ll misfire.
 

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2003 chevy trailblazer_lt_ext
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How do I go about checking the compression?
The best way to test compression is with a compression tester. Remove a spark plug and screw in tester. Crank engine. Make note of tester reading. Replace spark plug and remove another one. Screw in tester, crank engine and make note of tester reading. Do this at all 6 cylinders. Compare all the numbers. You want them to all be fairly close together. If one is substantially different, that cylinder has an issue. Cracked block, blown head gasket, etc.... This is what a compression tester looks like. Not that expensive...
54818
 

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Discussion Starter #8
You might have a problem with either the camshaft position sensor or the crankshaft position sensor. These are used to adjust the variable valve timing, so if they’re not working it’ll misfire.
I bought a new cam sensor, it wouldn’t go in all the way like the one that was in previously, the colored ring around the cam sensor seems like it won’t fit in. I’m gonna clean the hole and see if that helps. Would a cam sensor only cause one cylinder to misfire though? I cleared codes and let the engine run, ran the codes again and got a p0340 I believe, cam sensor circuit A. That’s the only code that popped up.
 

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Discussion Starter #9
The best way to test compression is with a compression tester. Remove a spark plug and screw in tester. Crank engine. Make note of tester reading. Replace spark plug and remove another one. Screw in tester, crank engine and make note of tester reading. Do this at all 6 cylinders. Compare all the numbers. You want them to all be fairly close together. If one is substantially different, that cylinder has an issue. Cracked block, blown head gasket, etc.... This is what a compression tester looks like. Not that expensive... View attachment 54818
Thanks for the instructions, I’ll go to autozone and grab one after I rule out the cam sensor. I’ve had someone tell me that my timing belt might be slipping. While the engine was running, the truck kept trying to die( very low rpms ). Is that an indicator of any serious problems?
 

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When doing a compression test, take ALL spark plugs out and test each cylinder one at a time, cranking the engine for about 5 seconds per test. After each test, release the pressure and test that same cylinder one to two more times for verification, then move on to the next cylinder. Leaving 5 plugs in will alter the test results and may give you false readings. One more thing, when checking a misfire on a single cylinder, I always swap the suspected bad coil with the one next to it and see if the misfire follows. A decent scan tool should have a data list feature that will show current cylinder misfire rate (how many times each cylinder is misfiring in a given timeframe in real time). If the coil swap doesn't change the misfire, swap the 2 plugs in the same manner you did with the coils. If it still doesn't change, it's likely either an injector issue, or compression issue. I can usually diagnose misfires correctly in 10-15 minutes, but sometimes I do need to swap injectors and that takes longer.
 
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