[SuperSound]

Originally Posted by Goal seeker

Pulling a plug wire would trigger a CEL because it's going to pick one up every other rotation. Do you think the EMS would react as fast on something that happens intermittently, and only when it's cold? My wife had a 2014 Grand Cherokee with a cylinder head problem that was notorious on the 3.6 Pentastars. I noticed a misfire a number of times before the CEL actually came on. Different make, different reactivity?

It's definitely fast enough, the question you meant...is it enough to trigger a code. Here's the code it would trigger and expectations generally:

"If the percentage of the increase or decrease in revolutions per minute (RPM) is between 2 percent and 10 percent, the Check Engine Light will come on. If the percentage of the increase or decrease in revolutions per minute (RPM) is greater than 10 percent, the Check Engine Light will blink on and off, as to alert the driver of a more serious misfiring problem. The P0300 trouble code indicates that there is a misfire in random or multiple cylinders."

Think about the programming for a sec. Based on the OP's description, if it happens that infrequently it's probably less than 1% in the 5-10mins when the engine is cold and running it's cold start program. To an engineer, that is not a problem. The problem would occur if it did not stop and continued which would trigger a code. Remember these cars are turned for emissions even under cold start. What some think is a miss could simply be the program adapting the timings/fuel, etc... as the engine temp increases.

But I have an even better reason to tell you not to worry, I've had 3 DI cars back to back. A VW 2.0T, BMW 2.0T, and now my LT1. Guess what, all 3 have this same issue on cold start. There are even threads about it on the BMW forums with lots of convinced it was a miss...only to spend months with their car in the shop and no fix. Then come to find out they were all new to DI. Some even noticed it on other DI cars they drove but assumed BMWs were perfect and shouldn't have this issue.

I won't sit here and tell you it isn't a miss. Instead I'll assure you if that is the only time you notice it and it doesn't trigger a light then you really have nothing to worry about. The engineers programed the conditions to trigger a code for a reason. Anything less than 2% isn't an issue.

[2K16SummitSS]

Don't worry, the car will tell you when there is a problem in the cold start sequence.
I went through this and had to have two injectors replaced. If you don't get codes then you are probably fine.

See my short thread below...
http://www.camaro6.com/forums/showth...ighlight=p0305

I'm now at 15,400 miles and running strong (knock on wood).

[Goal seeker]

Originally Posted by SuperSound

It's definitely fast enough, the question you meant...is it enough to trigger a code. Here's the code it would trigger and expectations generally:

"If the percentage of the increase or decrease in revolutions per minute (RPM) is between 2 percent and 10 percent, the Check Engine Light will come on. If the percentage of the increase or decrease in revolutions per minute (RPM) is greater than 10 percent, the Check Engine Light will blink on and off, as to alert the driver of a more serious misfiring problem. The P0300 trouble code indicates that there is a misfire in random or multiple cylinders."

Think about the programming for a sec. Based on the OP's description, if it happens that infrequently it's probably less than 1% in the 5-10mins when the engine is cold and running it's cold start program. To an engineer, that is not a problem. The problem would occur if it did not stop and continued which would trigger a code. Remember these cars are turned for emissions even under cold start. What some think is a miss could simply be the program adapting the timings/fuel, etc... as the engine temp increases.

But I have an even better reason to tell you not to worry, I've had 3 DI cars back to back. A VW 2.0T, BMW 2.0T, and now my LT1. Guess what, all 3 have this same issue on cold start. There are even threads about it on the BMW forums with lots of convinced it was a miss...only to spend months with their car in the shop and no fix. Then come to find out they were all new to DI. Some even noticed it on other DI cars they drove but assumed BMWs were perfect and shouldn't have this issue.

I won't sit here and tell you it isn't a miss. Instead I'll assure you if that is the only time you notice it and it doesn't trigger a light then you really have nothing to worry about. The engineers programed the conditions to trigger a code for a reason. Anything less than 2% isn't an issue.

This makes a lot more sense. Like any programming, it's not always all black and white. Thanks for the breakdown.

[SuperSound]

Originally Posted by Goal seeker

This makes a lot more sense. Like any programming, it's not always all black and white. Thanks for the breakdown.

No problem. Your question made think of it another way and realize there are "requirements" for the misfire codes to trigger.

[Bkmorey]

Just took my 2016 camaro 2ss to shop with 7k miles for misfire and on first start up it has a little bit of a extended crank. They said it's 100% a misfire even with CEL off and are trying a fuel injector they think is leaking

[SS 1LE]

Originally Posted by Bkmorey

Just took my 2016 camaro 2ss to shop with 7k miles for misfire and on first start up it has a little bit of a extended crank. They said it's 100% a misfire even with CEL off and are trying a fuel injector they think is leaking

Honestly, that is pretty odd...

I have never heard of a misfire in these cars not tossing a code, especially if an injector(s) is bad.

Also, LT1's at cold start will have a "rough" idle somewhat. It is the a/f ratio changing to heat the cats up faster. My previous Coyote Mustang did the same thing.

As for the extended crank, that also is normal. DI takes longer to build enough fuel pressure.

[mustangcrusher1]

My 2017 1SS does NOT do that at all, I would take it to the dealer. My 99 Z28 never did that either. just my experience....

[ChevyRules]

Originally Posted by Bkmorey

Just took my 2016 camaro 2ss to shop with 7k miles for misfire and on first start up it has a little bit of a extended crank. They said it's 100% a misfire even with CEL off and are trying a fuel injector they think is leaking

Extended start up on a cold start is normal. It is just building up fuel pressure before it goes to light off the engine.

[SS 1LE]

Originally Posted by mustangcrusher1

My 2017 1SS does NOT do that at all, I would take it to the dealer. My 99 Z28 never did that either. just my experience....

Your '99 Z28 was not DI, but I can guarantee you your LT1 takes longer to start. It HAS to as the fuel pressure is much higher. So that pressure needs to build. The colder it is outside, and the colder the car is, the longer it will take...this screenshot came right from a thread on the C7 forums from the head Corvette engineer.

[SuperSound]

Originally Posted by Bkmorey

Just took my 2016 camaro 2ss to shop with 7k miles for misfire and on first start up it has a little bit of a extended crank. They said it's 100% a misfire even with CEL off and are trying a fuel injector they think is leaking

I really hope you do actually have an issue but I can bet your car is going to spend all that time in the shop with no change. Unfortunately most dealer techs have little experience with the LT1 and while the trucks share similar engines, the tuning is quite different. And if they don't know about the extended crank times, they are already not showing themselves to be knowledgeable.

[mustangcrusher1]

Originally Posted by SS 1LE

Honestly, that is pretty odd...

I have never heard of a misfire in these cars not tossing a code, especially if an injector(s) is bad.

Also, LT1's at cold start will have a "rough" idle somewhat. It is the a/f ratio changing to heat the cats up faster. My previous Coyote Mustang did the same thing.

As for the extended crank, that also is normal. DI takes longer to build enough fuel pressure.

Fuel pressure or oil pressure?

[SuperSound]

Originally Posted by mustangcrusher1

Fuel pressure or oil pressure?

Fuel...DI requires much high fuel pressure to operate.

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[SSDan]

Originally Posted by SuperSound

Fuel...DI requires much high fuel pressure to operate.

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To add - unlike many other DI engines the LT1 uses a mechanical high pressure pump driven by a cam lobe at the rear of the camshaft. Sometimes the engine needs to crank a few times to spin that lobe to build sufficient pressure before the ignition fires.

[SuperSound]

Originally Posted by SSDan

To add - unlike many other DI engines the LT1 uses a mechanical high pressure pump driven by a cam lobe at the rear of the camshaft. Sometime the engine needs to crank a few times to spin that lobe to build sufficient pressure before the ignition fires.

There's also a booster between the tank right? Thought I heard that.

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