Car sputtering / hesitating
Thread Starter
Cruising
Joined: Nov 2022
Posts: 10
Likes: 2
Car sputtering / hesitating
Just purchased a 2008 c6 z06, car has rpm b3 cam, Frankenstein heads, head bolts, long tube headers. car ran fine when I got it, took it to the tuner to look over the tune he gave it the okay. I just changed the spark plugs and wires, the car currently had ngk tr6 plugs gapped at 0.04. I ordered new tr6 plugs they came gapped at 0.035 I gapped them to the 0.04 to match how the old ones were. did a new battery. car runs okay now, idle sounds a little different I cant quite tell why though. under slight acceleration around 3-4k rpms the car sputters / hesitates, let off the throttle and it goes back to normal. all connections are snug. ordered new coil packs and going to try that hopefully it fixes it, any help would be appreciated.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,595
Likes: 4,055
From: Cape Coral, Florida
Coil packs are pretty much bulletproof on these cars…this sputtering and hesitating can be caused by a few things…without at least a scan tool you’ll only be guessing and that can get expensive…I’d try something easy like cleaning the MAF and throttle body…may be cheaper in the long run to pay for an hours diagnostic time…I’d let a diagnostic shop handle this…not a repair shop or dealership..they will only replace parts and that may get expensive for you…where are you located ??..I know of some good diagnostic shops around the country.
Thread Starter
Cruising
Joined: Nov 2022
Posts: 10
Likes: 2
Located in Delaware. I have put 1000 miles on the car before doing the spark plugs and right after doing them I have this issue. leading me to believe something along those lines less than MAF / Throttle body since I've had no issues otherwise. the coil packs are quite brittle seems like the original ones from 2008, had the ends of 2 break off a little so going to replace them anyways, don't know if that makes a difference. its not a constant issue either, I can go up to and past 3k without any issue 9 out of 10 times. could be slight misfire but hard to tell because of the cam. I have a basic code reader and clearer that shows other information on it, never used it for much more than clearing codes. no check engine light assuming it is blocked off for misfire from the cam tune.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,595
Likes: 4,055
From: Cape Coral, Florida
Unless the ECM is counting a certain number of misfires from the crankshaft position sensor it will not show a misfire…if your code reader has a generic OBD2 function that may show misfires if you have any and your code reader has that capability…generic OBD2 has a check engine light symbol when you start up your scan tool…you don’t have to enter the year of the car, model etc…also don’t know if your code reader can graph data PIDS like O2 sensor voltage, MAF, TPS, fuel trims etc…that would be helpful looking at these things while you drive and these driveability issues crop up…unfortunately the code reader is not going to tell you what’s wrong but you will have to interpret the data it shows you.
Pro
Joined: Feb 2022
Posts: 635
Likes: 271
From: Hampton, VA
I'm going to agree with closing the spark plug gap back to where it was at .035 and seeing where you're at. but as also stated, it may be cheaper in the long run to pay that 1 hour diagnostic fee. Do you have HP-tuners at all? you can take some logs and it does a pretty good job of counting misfires, even if you aren't throwing any codes.
Melting Slicks
Joined: Nov 2009
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From: Klein TX
2023 C6 of the Year Finalist - Unmodified
2022 C6 of the Year Finalist - Unmodified
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Thread Starter
Cruising
Joined: Nov 2022
Posts: 10
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I’ve triple checked everything. All that was changed was the spark plugs which I put back in the same exact brand and type of plug with the same gapping as the old ones. Only other thing I’ve changed was the wires which are from summit racing. Plugs are in tight, wires are snug on the end of the spark plugs and fully on the coil packs. With the exact same spark plug setup the only other difference is the wires.
Granatelli Motor Sports GM High Performance Coil Near Plug Wire Sets 28-1811-HTR
Drifting
Joined: Aug 2022
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From: Ruskin, FL
I’ve triple checked everything. All that was changed was the spark plugs which I put back in the same exact brand and type of plug with the same gapping as the old ones. Only other thing I’ve changed was the wires which are from summit racing. Plugs are in tight, wires are snug on the end of the spark plugs and fully on the coil packs. With the exact same spark plug setup the only other difference is the wires.
Granatelli Motor Sports GM High Performance Coil Near Plug Wire Sets 28-1811-HTR
Race Director
Joined: Oct 2004
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Located in Delaware. I have put 1000 miles on the car before doing the spark plugs and right after doing them I have this issue. leading me to believe something along those lines less than MAF / Throttle body since I've had no issues otherwise. the coil packs are quite brittle seems like the original ones from 2008, had the ends of 2 break off a little so going to replace them anyways, don't know if that makes a difference. its not a constant issue either, I can go up to and past 3k without any issue 9 out of 10 times. could be slight misfire but hard to tell because of the cam. I have a basic code reader and clearer that shows other information on it, never used it for much more than clearing codes. no check engine light assuming it is blocked off for misfire from the cam tune.
Pro
Joined: Jan 2020
Posts: 623
Likes: 130
From: Az
Crank it up in a dark garage and look at each spark plug. You're looking for crossfire i.e. sparks outside the engine. I had this sort or situation years ago and the best diagnostic tech in Tampa FL couldn't figure it out. I found it by accident. One of the brand new spark plugs had a hairline crack in the porcelain.
Thread Starter
Cruising
Joined: Nov 2022
Posts: 10
Likes: 2
thanks for everyone’s responses. Like I had mentioned i had cracked coil packs. Replaced the coil packs and checked the spark plugs. Brand new Spark plugs were fouled from the broken coil packs. Put the old plugs back in which were in good shape. Coil packs seems to have created the issues and with the new packs everything is all good now.