Flashing check engine light

[PaulsSS]

I used my wifes v6 Camaro and since she drives so slow I thought I'd run it hard and blow the carbon out. Well that didn't go so well, I ran it hard up to red line and afterwards the engine started missing and check engine light flashing constant. So I pushed it to the floor and again, check engine light stops flashing and goes off but the engine is missing clearly not running on all cylinders. Its been about 75k since I changed the plugs so on the way home I picked up a set. Got scanner out number 5 cylinder miss fire. Pull all the plugs 95 degrees out I'm soaking wet. All the plugs looked good but worn some so I'm kind of puzzled but continue on replacing them. Use my scanner to erase the code and WALAA no more miss fire and it runs good. I'm a bit puzzled what actually happened at this point? Is it possible the computer shut down number 5 cylinder because of the miss fire and deleting the code restarts it?

I think maybe a piece of carbon may have shorted the plug temporarily but it was clean when I pulled it out.

[gtstorey]

I've never heard of a computer killing a cylinder due to misfire.

[xstuntman]

One plug went bad, no biggy and easy fix.
Yeah, a flashing check engine usually means a misfire.
I would run some CRC intake cleaner in it tho since direct injection motors do not "clean out" the carbon with lots of RPMs. Yeah, you actually made it worse as you found out.

[hunter1660]

Sounds like you need to stay out of your wife’s car… lol

[Aqua Blue RS/SS]

Originally Posted by hunter1660

Sounds like you need to stay out of your wife’s car… lol

Funny normally it’s the other way around

[sscamaro]

I had a problem with my 2017 Silverado a month ago. Check showed it was air/fuel ratio. Took it to the dealer and they didn't find anything wrong. It would appear and disappear for a couple of weeks. Now it has no appeared for 2 weeks. I did replace the air filter and put injector cleaner in it, so maybe it will OK now.

[PaulsSS]

Thanks for the replies, I put a bottle of Techron in last night and took it for a wild ride. Worked perfectly and put a guy in a Lexus in his place. Its a fun car to drive with that light weight v6 it really handles like a cat. I'm not sure about using the CRC intake cleaner product after reading 1000 or so reviews on Amazon. Some guys blocked their cats after using it.

[PaulsSS]

I talked with a local garage tech about this and he told me the computer shuts off the injector and the coil when a constant miss fire is detected to protect the cat. Erasing the code turns it back on as I suspected.

[NOT A 45]

Originally Posted by PaulsSS

I talked with a local garage tech about this and he told me the computer shuts off the injector and the coil when a constant miss fire is detected to protect the cat. Erasing the code turns it back on as I suspected.

This is exactly how it operates:

Extreme cylinder misfire events can cause catalytic converter damage. The malfunction indicator lamp (MIL) will flash when the conditions for catalytic converter damage are present. DTCs P0301 through P0306 correspond to cylinders 1 through 6. When the ECM detects that one or more specific cylinders are misfiring, the DTC for the respective misfiring cylinder will set and up to 2 of the corresponding fuel injectors are disabled for a minimum of 30 s. The ECM will then re-enable the fuel injector and, after approximately 200 engine revolutions, will determine if the misfire is still present. If the misfire is still present, the ECM will disable the fuel injector again repeating the process. If the misfire is not present, the fuel injector will remain enabled by the ECM. In Spark Ignition Direct Injection (SIDI) system applications, if a fuel injector fault DTC is set during a misfire event, the ECM will not re-enable the injector.


You have SIDI, so yes your assumption was correct.......cleared code eliminated your misfire. Something to keep in mind if your trying to diagnose this.... you will have spark but no injector pulse!

[Moto-Mojo]

Originally Posted by NOT A 45

This is exactly how it operates:

Extreme cylinder misfire events can cause catalytic converter damage. The malfunction indicator lamp (MIL) will flash when the conditions for catalytic converter damage are present. DTCs P0301 through P0306 correspond to cylinders 1 through 6. When the ECM detects that one or more specific cylinders are misfiring, the DTC for the respective misfiring cylinder will set and up to 2 of the corresponding fuel injectors are disabled for a minimum of 30 s. The ECM will then re-enable the fuel injector and, after approximately 200 engine revolutions, will determine if the misfire is still present. If the misfire is still present, the ECM will disable the fuel injector again repeating the process. If the misfire is not present, the fuel injector will remain enabled by the ECM. In Spark Ignition Direct Injection (SIDI) system applications, if a fuel injector fault DTC is set during a misfire event, the ECM will not re-enable the injector.


You have SIDI, so yes your assumption was correct.......cleared code eliminated your misfire. Something to keep in mind if your trying to diagnose this.... you will have spark but no injector pulse!

Fbodfather, et al notwithstanding, pretty cool that a GM tech hangs here and provides us with OE data and expertise.

[NOT A 45]

Originally Posted by Moto-Mojo

Fbodfather, et al notwithstanding, pretty cool that a GM tech hangs here and provides us with OE data and expertise.

Thanks, I like helping people when I can. It took me miss diagnosing a car in the past to learn this. Your LS engine doesn't do this but the high feature V6 does.

[PaulsSS]

45 what are your thoughts on using the CRC valve cleaner. Engine is at 130k last walnut blasted at 90k. Runs excellent, I really can't notice any loss of power.

[NOT A 45]

Originally Posted by PaulsSS

45 what are your thoughts on using the CRC valve cleaner. Engine is at 130k last walnut blasted at 90k. Runs excellent, I really can't notice any loss of power.

Can't imagine it would hurt anything.....what we use at the dealer is upper engine and fuel injector cleaner p/n 88861803 and it's very effective! Pulled through a vacuum hose with the engine idling and about to stall, turn it off and let it set for a couple hours. Then restart and suck the rest of the bottle to finish cleaning it out seems to correct all random misfires due to carbon.

[PaulsSS]

Ok Thanks will do.