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10-06-2010, 05:37 PM #1
Help! Loud tick / pop only when #1 cylinder fires...
I've had a loud tick, really more of a "pop" develop after a trip to the track. I don't think that it is metal on metal, sounds almost electrical. I have isolated it to the #1 cylinder, and what is interesting, it is completely ON or OFF depending on whether the cylinder is firing... i.e. when plug wire is on, POP POP POP, when plug wire is off... no noise... or at least not enough to detect.
What I have done so far...- change plug on #1 cylinder
- ensure plug is fully and properly threaded
- swap plug wires
- swap coil packs
None of the above made a difference. Still ON / OFF if cylinder was firing or not.
Then I checked the header bolts to ensure they were tight, no issues there, headers on tight.
I don't think its an arcing issue because swapping plug wires doesn't help.
Then I held my breath and pulled the valve cover - fortunately didn't see any metal or evidence of damage and there was no play in the rockers, push rods, etc.
Only thing I haven't done is swap injectors... but I don't have much confidence that's the problem.
Engine is an L92 bored/stroked to 427, TFS 235 heads, cammed, kooks headers, FAST 92 intake.
Help... anyone? What should I check next? If it is valvetrain or bottom end damage wouldn't it still be loud with the cylinder not firing?
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10-07-2010, 02:46 AM #2
with nosie like that I shut down each cyl till the noise changes & thats ur cyl...because when u take away the firing pressure on the piston the sound will change..could be bottom end....
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10-07-2010, 03:55 AM #3
check the compression on 1 and see what it shows
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10-07-2010, 06:06 AM #4
I have isolated it to the #1 cylinder, I'm sure of that. I threw a rod bearing on a difference motor a few years ago - definitely a different sound than what I have now.
Did that, forgot to mention. I think #1 was 170 and #2 was 160, so compression seemed fine.
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10-07-2010, 03:12 PM #5
Just swapped injectors... noise is still there. It goes away at higher rpms... but is very loud at idle and < 2,000 rpms or so.
If a lifter is stuck would the noise almost completely go away if the cylinder isn't firing... or would it still be present? Noise seems to be coming from under the intake and injectors so I'm wondering if it could be a lifter.
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10-07-2010, 03:54 PM #6
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10-07-2010, 04:05 PM #7
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Phantom Black Metallic- 2004 GTO M6
Did you run the car to redline while at the track?
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10-07-2010, 04:06 PM #8
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Phantom Black Metallic- 2004 GTO M6
I know some techs use soapy water in a spray bottle to spray on the wires to see if there is any arcing.
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10-07-2010, 06:41 PM #9
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10-07-2010, 06:49 PM #10
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10-07-2010, 06:54 PM #11
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Phantom Black Metallic- 2004 GTO M6
I think the suds make the spark brighter to see if there are any breaks in the wire insulation if I recall.
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10-09-2010, 01:54 PM #12
ttt...
Is there any way to diagnose lifter or pushrod damage without pulling the head? I pulled the valve cover didn't see any metal shavings, no obvious play in the springs, rockers, etc.
Also, would minor valvetrain damage go away with some rpms? My noise is present at idle and low rpms... but goes away with some rpms.
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10-10-2010, 07:50 AM #13
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Phantom Black Metallic- 2004 GTO M6
I think you have to pull the pushrods to see if they are bent. Others here have posted here about how to go about removing the pushrods to check for bent ones.
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10-10-2010, 08:26 AM #14
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10-10-2010, 02:38 PM #15
OK, removed the valve cover & yella terra's on cylinder #1. Pulled the 2 push rods and rolled them on granite counter top, rolled straight and true, I don't think its a bent push rod issue.
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10-10-2010, 03:00 PM #16
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Phantom Black Metallic- 2004 GTO M6
OK. When you pulled the plug on cylinder #1, were there any shavings on the plug? Like as if the threads had pulled out of the head? Also, check the harness to the coil on cylinder #1 to see if there is sufficient current going to that coil. There could be a chafed wire somewhere.
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10-10-2010, 04:53 PM #17
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10-10-2010, 04:55 PM #18
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Phantom Black Metallic- 2004 GTO M6
If there are no shavings, and the plug is snug in the head, then I am thinking there is a short somewhere in that harness going to cylinder #1 coil.
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10-11-2010, 09:22 AM #19
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Did you inspect the springs when the valve cover was off? Look them over thoroughly as a broken spring can sometimes be difficult to see when installed.
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10-11-2010, 12:20 PM #20
i had a broken spring on an 02 firehawk of my buddies and it missed bad and backfired . doesn't really sound like a broken spring but maybe. if you pull the plug wire at the coil it should arc out of the coil if it is firing..
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