[RamAir02]

Had a DE event at Watkins Glen this past weekend. The car started throwing a P0300 code on Sunday and was breaking up at high RPMs -- flashing CEL, misfiring.

I cleared the code and went back out on track, same issue. I disconnected the battery for 10 mins and went back out on track, same issue.

The car drives fine at low RPMs, but starts breaking up above 4500-5000 RPMs. I took the car to the dealer since she's still under powertrain warranty. They said they detected 115 misfires on cylinder 2. If the issue is indeed on cylinder 2, I'm not sure why the code wouldn't throw a more specific code to indicate the cylinder, i.e. P0302, instead of a generic random / multiple misfire code, P0300.

The tech replaced the spark plug and said that the old one looked ok, but the gap was a bit big. I've never touched the plugs -- they're factory. They also swapped cylinder 2 coil pack with cylinder 4 in case that's the issue.

I wish they were able to further diagnose the issue. I have a feeling I'm going to run into the same issue at my next track event which will ruin the weekend.

Has anyone seen this issue before? Car is mostly stock (mods in sig). I thought it might be a sticking injector or something fuel related, but it doesn't seem they did anything to diagnose the fuel system.

[LiqTenExp]

Some issues to look out for when I've had similar oddities with misfires that go beyond the obvious ones you've covered:

1) Coil pack pin within connector not locked in place and backed out (only had misfires at high RPM), would appear in place when not connected (had to do a pull test on the back of each wire to verify they were locked)
2) Plug wires not fully inserted (should get 1 click on plug and 2 clicks on coil pack with stock plug wires)
3) Bad Injector (this was a mid-RPM misfire for me)

If you start seeing the misfire code + differential errors reported on screen that is just a misfire, nothing wrong with diff. May be worth replacing battery for this one.

I assume you are on stock tune based your mod list?

[RamAir02]

Originally Posted by LiqTenExp

Some issues to look out for when I've had similar oddities with misfires that go beyond the obvious ones you've covered:

1) Coil pack pin within connector not locked in place and backed out (only had misfires at high RPM), would appear in place when not connected (had to do a pull test on the back of each wire to verify they were locked)
2) Plug wires not fully inserted (should get 1 click on plug and 2 clicks on coil pack with stock plug wires)
3) Bad Injector (this was a mid-RPM misfire for me)

If you start seeing the misfire code + differential errors reported on screen that is just a misfire, nothing wrong with diff. May be worth replacing battery for this one.

I assume you are on stock tune based your mod list?

Thanks for the additional thoughts.

Battery is an interesting topic -- I've seen other threads where the issue was the battery. I'm running an Antigravity 40 Ah battery. It's only about six months old and is always on an OptiMate maintainer when the car is not being driven.

Tune is stock.

[LiqTenExp]

Originally Posted by RamAir02

Thanks for the additional thoughts.

Battery is an interesting topic -- I've seen other threads where the issue was the battery. I'm running an Antigravity 40 Ah battery. It's only about six months old and is always on an OptiMate maintainer when the car is not being driven.

Tune is stock.

Sounds like you shouldn't worry about battery or tune.

That first one had me going for a loop. I did swap coils and it worked, for a little, it just wound up being a slightly better connection till it worked its way off and started crapping out again at high RPM.

[SFV1LE]

So the dealer swapped coils between 2 cylinders? How would that improve things if they do it assuming one of them might be bad? I assume the goal to see if the issue occurs on the other cylinder so they can pinpoint a problem with the coil?

Can you take your car somewhere remote where you can really run it hard to simulate repeated track-like acceleration and get it very hot, so you can test the work they did? If not I recommend taking it to a dyno with a tech who really knows track prep, they can run it out to redline there and simulate track accelerations, Katech knows how to do this I assume others do too.

I have Willow Springs skidpad (which is really like a small oval track) only 75 min away and I sometimes take my car there to shake it down and practice car control prior to a track weekend. It's test and tune open track rules at the skidpad so very informal.

[RamAir02]

Originally Posted by SFV1LE

So the dealer swapped coils between 2 cylinders? How would that improve things if they do it assuming one of them might be bad? I assume the goal to see if the issue occurs on the other cylinder so they can pinpoint a problem with the coil?

Can you take your car somewhere remote where you can really run it hard to simulate repeated track-like acceleration and get it very hot, so you can test the work they did? If not I recommend taking it to a dyno with a tech who really knows track prep, they can run it out to redline there and simulate track accelerations, Katech knows how to do this I assume others do too.

I have Willow Springs skidpad (which is really like a small oval track) only 75 min away and I sometimes take my car there to shake it down and practice car control prior to a track weekend. It's test and tune open track rules at the skidpad so very informal.

Yes, exactly. Dealer swapped coils to see if the misfire jumps to cylinder 4. Their reasoning for doing this is since they cannot reproduce the misfire.

Unfortunately, I don't have an open area to do some testing. My next DE event is in a couple of weeks, so getting to a dyno before then will likely be tough.

At this point, I'm planning to do a few things:
1. Run some Techron through the fuel system in case my issue is related to a dirty / stuck injector
2. Purchase a spare ignition coil to have on hand at the track
3. Bring spark plugs & gap tool to the track
4. Get a more advanced OBDII scanner?

On that last point, I don't need HP Tuners, but is there laptop software or a handheld scanner that will give me more information than what I currently have? My scanner is an Autel AL319

[ZLRob]

Iridium plugs have a tendency to open their gaps when high demand is required of them. Conversely, Rutheniums actually close some.

As for your misfire issue I see cylinder 2 and 7 are the common culprits when it comes to misfires. I don't know how many miles you have on them nor did you list how many miles you have on the vehicle, but if all you do is use it for track duty, I would change them. I also would consider switching over to Rutheniums if gaps are a concern to you given the fact that they cost the same as Iridium's and in some situations, may even cost less. I would rather deal with an issue where the plugs slightly close rather than open. Plus the projected square tip design helps ignite things for the boost a little better anyway.

I don't know what sort of "go" mods you have on your vehicle or if you ever even plan on adding any, but this is also your chance to put a heat range 6 plug in there instead of the 5's (assuming your engine is all stock), which are not necessarily correct for the engine anyways.

[RamAir02]

Originally Posted by ZLRob

Iridium plugs have a tendency to open their gaps when high demand is required of them. Conversely, Rutheniums actually close some.

As for your misfire issue I see cylinder 2 and 7 are the common culprits when it comes to misfires. I don't know how many miles you have on them nor did you list how many miles you have on the vehicle, but if all you do is use it for track duty, I would change them. I also would consider switching over to Rutheniums if gaps are a concern to you given the fact that they cost the same as Iridium's and in some situations, may even cost less. I would rather deal with an issue where the plugs slightly close rather than open. Plus the projected square tip design helps ignite things for the boost a little better anyway.

I don't know what sort of "go" mods you have on your vehicle or if you ever even plan on adding any, but this is also your chance to put a heat range 6 plug in there instead of the 5's (assuming your engine is all stock), which are not necessarily correct for the engine anyways.

This is great info -- thanks. The car has 14.5k miles on her, mostly track miles and travel miles to/from the track. She pretty much sits in the garage between track events.

No "go" mods planned in the near future and the only borderline "go" mod on the car today is a RotoFab CAI. Instead of making the car quicker, I'm focused on my driver skill.

Would I still benefit from a step colder plug for track duty? Is the NGK LTR6AHX the one step colder Ruthenium plug you're referring to? I see they're gapped at .043" -- I believe stock LT4 gap is .032". What gap would I run these at?

[ZLRob]

Originally Posted by RamAir02

This is great info -- thanks. The car has 14.5k miles on her, mostly track miles and travel miles to/from the track. She pretty much sits in the garage between track events.

No "go" mods planned in the near future and the only borderline "go" mod on the car today is a RotoFab CAI. Instead of making the car quicker, I'm focused on my driver skill.

Would I still benefit from a step colder plug for track duty? Is the NGK LTR6AHX the one step colder Ruthenium plug you're referring to? I see they're gapped at .043" -- I believe stock LT4 gap is .032". What gap would I run these at?

Right. Driver mod is everything.

So the car is driven hard mostly all the time. That usually demands intense spark all the time and may be the cause of your issues. Though I'm not there and can't diagnose your issue without physically putting my hands on the car. Given the mileage I would place the blame on the plugs before anything else. My old GTO and several other LS cars I had had misfires caused by the factory plugs at low mileages.

The part number you listed to me was for the double fine end (DFE) Ruths. You want the LTR6BHX/ 90495's (PSPE). Those have a gap of .031 since they are meant for boost applications and NGK knows boost requires smaller gaps to prevent misfires. Run them as is and you should be pretty happy with them. They also should last longer as well. Pull plug #1 in about 500-1000 miles and inspect it just to see how they are doing.

Just to give you an idea of the heat range on the plugs, the LT1 equipped Camaro SS runs the same heat range 5 plug as the ZL1. That is a big red flag for me right there considering the 200 HP difference right out of the gate, as the general rule is to run one step colder per every 100-150 HP and seeing as pretty much all tuners recommend heat range 7 plugs for guys running 600 wheel HP and over, the stock heat range is definitely way too hot for the LT4 at 550-570 wheel HP.

One more thing, since you track this car and need all the cooling help you can get given how these blowers heat soak quick, I would run an external low temp radiator coolant tank of some sort for the blower. It's not a "go" mod, but more of a supporting mod for the system as whole.

[RamAir02]

Awesome. I appreciate the detailed explanation.

I'm going to grab eight NGK 90495 plugs -- rockauto seems to have the best price at the moment -- and swap them in before my next DE event.

Originally Posted by ZLRob

Right. Driver mod is everything.

One more thing, since you track this car and need all the cooling help you can get given how these blowers heat soak quick, I would run an external low temp radiator coolant tank of some sort for the blower. It's not a "go" mod, but more of a supporting mod for the system as whole.

I have the ADM Intercooler Reservoir v2, however, I don't believe it provides any additional cooling. I purchased it to ensure I never have air in the IC system.

[ZLRob]

Originally Posted by RamAir02

Awesome. I appreciate the detailed explanation.

I'm going to grab eight NGK 90495 plugs -- rockauto seems to have the best price at the moment -- and swap them in before my next DE event.



I have the ADM Intercooler Reservoir v2, however, I don't believe it provides any additional cooling. I purchased it to ensure I never have air in the IC system.

The additional coolant provides reserve volume for the system. It is to help for air in the system indeed, but it does have additional side benefits. Additionally I would also consider switching to water wetter/ engine ice, as water has better heat displacement benefits over ethylene glycol coolant, the boiling point of water is lower than coolant, however, making it difficult for full on water to operate properly in cooling systems. That plus it's inability to prevent corrosion and that's where the water wetter/ engine ice comes in.

Let me know how your spark plug deal turns out when you do them! I'm looking forward to hearing your results with them.

[wakespeak]

I had this.

1) Ended up replacing both 02 sensors and I think passenger side twice. The sensors could have gotten fouled during break in or 2-5 below.
2) I also got the SC coolant circuit reservoir as I think there was some engine management kicking in that was fouling the system.
3) I also replaced the battery. Check that your volts drop to 12 when driving after about 20 mins meaning your battery has enough charge for the alternator to put itself on hold. My battery got to where I wouldn't see the 12v (stayed at 14v) except rarely.
4) Put back in the fuse controlling the exhaust flap (so now it is factory). Thread on if missing misc electrical issues occur somewhere here.
5) Reduced antifreeze ratio to about 35%-40% for better heat transfer, hoping less ignition retard kicking in.

Not sure what was affecting things the most. Anyways all good now 17k miles about half on track.

Edit: in terms of fuel, I try to fill up mostly at the pump under the assumption that there is enough 87 in the fuel line to dilute the premium. At the track the fuel can be dodgy. At COTA they switched to another supplier from whatever the earlier company was. The new supplier put 10% ethanol fuel into previously ethanol free 93 octane. This caused one of my rough running 02 sensor killing episodes I am almost sure as clearing the codes helped nothing after that weekend. After 02 change everything was fine. Same happened at the marina with our boat. They switch to ethanol mix which pulled all the water and junk out of the tanks immediately stranding us and a lot of other folks in the water with a clogged fuel filter.

Another edit - The passenger side 02 sensor connector was about an inch away from the factory exhaust. When I replaced it I was able to get it farther away. Anyways good luck!

[RamAir02]

Originally Posted by wakespeak

I had this.

1) Ended up replacing both 02 sensors and I think passenger side twice. The sensors could have gotten fouled during break in or 2-5 below.
2) I also got the SC coolant circuit reservoir as I think there was some engine management kicking in that was fouling the system.
3) I also replaced the battery. Check that your volts drop to 12 when driving after about 20 mins meaning your battery has enough charge for the alternator to put itself on hold. My battery got to where I wouldn't see the 12v (stayed at 14v) except rarely.
4) Put back in the fuse controlling the exhaust flap (so now it is factory). Thread on if missing misc electrical issues occur somewhere here.
5) Reduced antifreeze ratio to about 35%-40% for better heat transfer, hoping less ignition retard kicking in.

Not sure what was affecting things the most. Anyways all good now 17k miles about half on track.

Edit: in terms of fuel, I try to fill up mostly at the pump under the assumption that there is enough 87 in the fuel line to dilute the premium. At the track the fuel can be dodgy. At COTA they switched to another supplier from whatever the earlier company was. The new supplier put 10% ethanol fuel into previously ethanol free 93 octane. This caused one of my rough running 02 sensor killing episodes I am almost sure as clearing the codes helped nothing after that weekend. After 02 change everything was fine. Same happened at the marina with our boat. They switch to ethanol mix which pulled all the water and junk out of the tanks immediately stranding us and a lot of other folks in the water with a clogged fuel filter.

Another edit - The passenger side 02 sensor connector was about an inch away from the factory exhaust. When I replaced it I was able to get it farther away. Anyways good luck!

Thanks for sharing your experience. The o2 sensors potentially being the issue jumps out to me -- I've had P015D codes in the past that I've cleared a few times. That code has only popped up with low RPM driving / babying the car. I've never had the P015D during or after a track session.

[VaporPressure]

Have you noticed any increased engine noise? Prior to track days I had new mild ticking that sounded a lot like "normal" lifter tick. No codes with regular driving, the P0300 code only threw at the track, with a "service rear axel" warning. Swapped all the spark plugs, which looked fine at 14k miles. Eventually they found out the camshaft had been damaged, a lobe had flaked off. Service guy said he hadn't seen that happen before though.