C6 Running Terrible
Thread Starter
Burning Brakes
Joined: Apr 2008
Posts: 1,190
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From: Woodland Hills California
C6 Running Terrible
I just finished installing my Z06 exhaust and now my car runs rough. Has several codes related to O2 sensor (fixed those) and a missfire code P0300. I had to disconnect the spark plugs to change the exhaust manifolds. Think I might not have a spark plug hooked up properly. I have checked all of them and they are tight. Could one or more still not be plugged in?
John
John
Safety Car
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From: Location: Location: kAnSaS
you might have hit a plug and cracked the porcelain part which causes it to missfire down the side of itself. pretty common on plugs that have solid cores (if you do) this will set missfire codes everytime. If not that then check the wires and make sure one isnt torn or ripped. Should be easy to find. If you have a scanner find which cylinder is missfiring and go right to that one. good luck ,paul
Thread Starter
Burning Brakes
Joined: Apr 2008
Posts: 1,190
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From: Woodland Hills California
The code I got is P0300, engine missfire detected. I was hoping for a cylinder(s) missfire code (P0301-0308), but no luck. My code reader can't link up to CAN protocol, so had to use OnStar. I was careful not to hit a plug with the manifold, but it could have happened. I would think that a broken plug would definitely show up with a specific cylinder missfire. It also seems pretty hard not to get the connectors hooked up to the plugs.
John
John
Thread Starter
Burning Brakes
Joined: Apr 2008
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From: Woodland Hills California
I will try disconnecting one coil at a time with the engine running and see if one or more makes no difference in the engine operation. That should tell me where to focus my attention.
Le Mans Master
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From: Rochester New York
Race Director
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Safety Car
Joined: Sep 2008
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From: Location: Location: kAnSaS
look at one of these things to be your isssue in this order, plug, wire, coil disconnected or bad, injector issue, computer issue, wiring issue. doubt you will go past the first 3 items. good luck, it happens to us all. paul
Thread Starter
Burning Brakes
Joined: Apr 2008
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From: Woodland Hills California
OK, I disconnected each coil while idling and noticed a little difference on the left bank, not much on the right bank. I also hooked a timing light up to each plug wire and observed steady light flashes from gun. Still has a missfire. If a plug was broken (porcelain cracked), that should kill that plug, right? Guess the next step is to remove each plug and visually check for damage. Can the plug wire to spark plug connection be off? The connectors are on tight - very difficult to unplug, so I think they are installed properly. I did not disconnect the coils when I replaced the exhaust manifolds. Just unplug the spark plugs.
John
John
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OK, I disconnected each coil while idling and noticed a little difference on the left bank, not much on the right bank. I also hooked a timing light up to each plug wire and observed steady light flashes from gun. Still has a missfire. If a plug was broken (porcelain cracked), that should kill that plug, right? Guess the next step is to remove each plug and visually check for damage. Can the plug wire to spark plug connection be off? The connectors are on tight - very difficult to unplug, so I think they are installed properly. I did not disconnect the coils when I replaced the exhaust manifolds. Just unplug the spark plugs.
John
John
At this point I would try new plugs on the right side and see what happens. Have you pulled any plugs yet to check for fouling?
Le Mans Master
Joined: Sep 2008
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From: Stafford VA, home of our wolf den. No house break ins to date.
what year is your vette? how many miles on it? why do I ask? starting to sound like it could be one or more wires... none got kinked, right?
Melting Slicks
Joined: Jul 2007
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From: Brentwood World's first A6 in the 9's (including N/A, blower, turbo and nitrous cars) 9.950@139.267 CA
OK, I disconnected each coil while idling and noticed a little difference on the left bank, not much on the right bank. I also hooked a timing light up to each plug wire and observed steady light flashes from gun. Still has a missfire. If a plug was broken (porcelain cracked), that should kill that plug, right? Guess the next step is to remove each plug and visually check for damage. Can the plug wire to spark plug connection be off? The connectors are on tight - very difficult to unplug, so I think they are installed properly. I did not disconnect the coils when I replaced the exhaust manifolds. Just unplug the spark plugs.
John
John
It did however drop the idle a bit when I pulled the wire while the car was running.
Drifting
Joined: Oct 2004
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From: STL MO
St. Jude Donor '09-'10
That is the same way mine reacted, a broken plug seems more noticeable than a cracked wire which seems more problematic under load.
Like FortMorganAl said probably time to change the plugs on that side and go from there.
Thread Starter
Burning Brakes
Joined: Apr 2008
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From: Woodland Hills California
It is an 08 with 19,000 miles. I did not notice much change when I unplugged the right bank coils (one at a time) but could detect a slight increase in idle when I plugged each back in. Did not seem to notice the same thing on the left (drivers) bank. If I bring the engine speed up around 1300 rpms with no load, I can detect a slight miss. It is, of course, much more noticeable when driving. Also, I get a Check Traction Control warning on the dash display. Is this related to a misfire?
Can't imagine having damaged the wires. Could something happen to them unplugging from the spark plugs? They took considerable twisting and pulling to unplug.
Can't imagine having damaged the wires. Could something happen to them unplugging from the spark plugs? They took considerable twisting and pulling to unplug.
Safety Car
Joined: Sep 2008
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From: Location: Location: kAnSaS
It is an 08 with 19,000 miles. I did not notice much change when I unplugged the right bank coils (one at a time) but could detect a slight increase in idle when I plugged each back in. Did not seem to notice the same thing on the left (drivers) bank. If I bring the engine speed up around 1300 rpms with no load, I can detect a slight miss. It is, of course, much more noticeable when driving. Also, I get a Check Traction Control warning on the dash display. Is this related to a misfire?
Can't imagine having damaged the wires. Could something happen to them unplugging from the spark plugs? They took considerable twisting and pulling to unplug.
Can't imagine having damaged the wires. Could something happen to them unplugging from the spark plugs? They took considerable twisting and pulling to unplug.
Pro
Joined: Nov 2005
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From: Sapulpa Oklahoma
You can damage the wires by pulling on the wire instead of the insulator. Not hard to kill one. You can remove them all and test with an ohm meter (wiggle each end while testing) They all should read very close to the same. A broken one will show up with high resistance.
Team Owner
Joined: Mar 2008
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From: Southern Utah
You can damage the wires by pulling on the wire instead of the insulator. Not hard to kill one. You can remove them all and test with an ohm meter (wiggle each end while testing) They all should read very close to the same. A broken one will show up with high resistance.
Very easy to damage a wire in the pulling process. Take each one and check it with ohm meter. doesn't matter what the reading is, it will be the different one that is bad. And with regard to plugs, just buy one new one and try it in each cylinder. They are easy to get to, and at 19000 miles, you are 81000 away from needing new plugs so don't buy more than the one.
Le Mans Master
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