[colsoncj]

So, my SS has developed a new symptom/issue that I haven't quite figured out yet. 6M, LT1, 11k miles.

When cold, at very light throttle at any speed between 5 and 60, the car will hesitate, stumble, and jerk, almost like a misfire or stall. Could also be better explained as a shudder. No CEL yet.

I haven't noticed yet when its warm, but its only done it a handful of times so I don't have a lot of data points to say its only a cold engine issue.

I do know it will do it at any RPM. If you apply a significant amount of throttle, it comes to life like it should and has no issues pulling hard to redline. Only appears to have the issue if you are driving normally and don't require more than about 1/4 throttle.

Wondering if it could just be a bad tank of gas, but it doesn't do it every time, and I can't say for sure it's all been on the same tank (it doesn't get driven a whole lot). Currently running a bottle of Chevron Techron thru it now to see if that clears anything up.

Any thoughts, things to check or look at?

[colsoncj]

So dug into it a little more today. Pulled the scanner, found a pending P0300 code for multiple misfires, which makes sense given how it was acting.

I then fired it up, let it warm up a little more and drove it today... It was warmer outside today too. Had one small stumble right after puling onto the road, but then nothing after that - not even a little hiccup or stumble. I'm wondering if it just doesn't like the cold, needs warmed up more...

I'll post back if it happens again, or any more codes pull up - but still welcome any advice if it does.

I'm guessing, if it does come back - Check:
- Coil connections
- Plug wire connections
- Injector issue (connection, sticky, dirty)
- Fuel issue (dirty/bad)
- Plugs fouled (leaning towards this one personally given how little its driven)

Anything else?

[NewCamaroOrder]

Start simple. How is your air filter?
What oil are you running? I switched to the 0w-40 Mobil1 ESP as soon as GM mandated it for LT1 engines. I'm not sure how that oil does in the cold as I live in CA.
You could run a bottle of injector cleaner in case is was bad gas.
If you're not running a Catch Can you may need to clean the intake track?

A couple relatively simple items to check.

FYI, I have the A8 shudder, she's at the dealership getting flushed per the TSB, and it usually presents once the engine is warm. When its cold I don't really feel it.

Good Luck!

[colsoncj]

Originally Posted by NewCamaroOrder

Start simple. How is your air filter?
What oil are you running? I switched to the 0w-40 Mobil1 ESP as soon as GM mandated it for LT1 engines. I'm not sure how that oil does in the cold as I live in CA.
You could run a bottle of injector cleaner in case is was bad gas.
If you're not running a Catch Can you may need to clean the intake track?

A couple relatively simple items to check.

FYI, I have the A8 shudder, she's at the dealership getting flushed per the TSB, and it usually presents once the engine is warm. When its cold I don't really feel it.

Good Luck!

Air Filter was good when I checked it for the last oil change.
Oil is Valvoline Full Synthetic 5W30 (no tracking), changed at least yearly.
Current tank does have a bottle of Techron Fuel System Cleaner already in it

I am leaning towards oil collection/plug fouling at the moment. I don't run a catch can, but have considered it. I may pull a couple of plugs and or the intake to have a look. If thats the case, a catch can may be in order.

[SomeGeoffGuy]

Do you have headers? All my experiences with problems like this involve headers (not factory but long tubes).

-Geoff

[colsoncj]

Originally Posted by SomeGeoffGuy

Do you have headers? All my experiences with problems like this involve headers (not factory but long tubes).

-Geoff

Nope - 100% stock.

[SomeGeoffGuy]

Originally Posted by colsoncj

Nope - 100% stock.

That is an odd one then! I have seen that behavior with cracked spark plugs and burned wires. Happens all the time with header installs.

-Geoff

[JimRockford]

i'll go with: injector - verify it by snifftest after you park - do ya smell gasoline then or at other random times? there should never be any gasoline smell whatsoever.

other idea is plug/foul. 2017 is 5 years. is there a time-limit on plug-swap? its 100k miles probably, but after certain # of years, gotta inspect/swap all sorts of stuff

[NewCamaroOrder]

I took my 2017 into dealership for A8 shudder and they said I had rough idle on cold start and I needed new injectors. They are going warranty it for me under my extended warranty.

Just a thought.

[colsoncj]

Wanted to come back to this... as the temps warmed up, issue went away. Seems to only affect the car when its cold and cranky. Driven it a few more tanks and no return... so who knows!

[ctrlz]

The closest you got to CEL was a pending P0300. That's multiple random misfires, but not enough events or persistence to trigger a CEL. No isolation to bank 1 or bank 2.
My car has always had intermittent misfires when cold, particularly during the first minute after startup. Never got a CEL. I just take it easy like I do with all engines until I get some heat into them.

Originally Posted by colsoncj

Had one small stumble right after puling onto the road, but then nothing after that - not even a little hiccup or stumble. I'm wondering if it just doesn't like the cold, needs warmed up more...

This is pretty much every morning for me!

[colsoncj]

Originally Posted by ctrlz

The closest you got to CEL was a pending P0300. That's multiple random misfires, but not enough events or persistence to trigger a CEL. No isolation to bank 1 or bank 2.
My car has always had intermittent misfires when cold, particularly during the first minute after startup. Never got a CEL. I just take it easy like I do with all engines until I get some heat into them.


This is pretty much every morning for me!

Basically my thought... let it warm up, take it easy, and no issues!