When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I am having an issue where the engine misfires at idle, you can feel it, however there is no MIL. My Icon T8 scanner as well as my old HpTuners MPVi do not report the misfire streaming data. I have not owned the car but a couple weeks 35K miles 2019 Stingray M7. I am at a loss here and I was really hoping you guys can send me in the right direction.
Replaced the plugs with NGK Iridium ix LTR5ix-11, as well as the AC delco spark plug wires with OEM.
I did notice the IAT on the high side 140+ even when idling in driveway for an extended period. Threw this out as the misfire is present just after warmup and IAT are low. Ambient around 90 degrees (Dallas Fort-Worth TX)
Mild exhaust leak, can only really hear it up again a fast food drive through wall. Seems it is at the "collector" on LH side.
Both B1 and B2 02s are oscillating, while my LTFT is -11 to -14.
It seems the misfire is worse after a highway run or long drive. Driveablily really doesn't seem all that affected, other than a couple spots in the lower RPM. Assumming I am really being critical and trying to feel it just out of 1st gear.
The only modification I have found so far is the K&N cold air with box. No codes present even non-Mil.
Unfortunately we can’t diagnose it for you…so your scan tool shows no misfires in live data when you think it’s misfiring or it does not have misfire reporting at all ???…I’m not familiar with that scan tool…look in generic OBD2 Mode 6 and see if it shows misfires there…with elevated IAT’s and negative fuel trims and well as elevated MAP sensor readings may be a cat they may be getting clogged…any loss of power ??…other than plugs and wires the DIY’er won’t have much luck diagnosing a misfire without specialized diagnostic equipment so my direction for you is to find a diagnostic specialist in your area.
Unfortunately we can’t diagnose it for you…so your scan tool shows no misfires in live data when you think it’s misfiring or it does not have misfire reporting at all ???…I’m not familiar with that scan tool…look in generic OBD2 Mode 6 and see if it shows misfires there…with elevated IAT’s and negative fuel trims and well as elevated MAP sensor readings may be a cat they may be getting clogged…any loss of power ??…other than plugs and wires the DIY’er won’t have much luck diagnosing a misfire without specialized diagnostic equipment so my direction for you is to find a diagnostic specialist in your area.
The scanner has about the same bidirectional functionality as my old Snap On Solus Ultra, sold that some time ago. Do these engines have known valve issues? Other than a leak down/compression is there anything else I do? I want to do the exhaust and get the car tuned. Or I can have a shop to the cam springs and lifters. I just don't have the time in this hot garage to pull a motor. Shouldn't have to with 36k on the clock. I can't pay for a Kooks setup and the cam at the same time. Would be one or the other, each potentially fixing the issue.
If you have the LT1 no valve issues I know of except for the LS7’s on the C6’s…with the VVT and with GDI that will be a little difficult for you to diagnose….you can do a clear flood crank and listen for a uneven cranking cadence…just hold the gas pedal to the floor and try starting the car…it will only crank…below is an 2013 LS7 with a broken valve spring I looked at a few weeks ago…should not sound like this…before doing any mods I’d get this issue looked at.
If you have the LT1 no valve issues I know of except for the LS7’s on the C6’s…with the VVT and with GDI that will be a little difficult for you to diagnose….you can do a clear flood crank and listen for a uneven cranking cadence…just hold the gas pedal to the floor and try starting the car…it will only crank…below is an 2013 LS7 with a broken valve spring I looked at a few weeks ago…should not sound like this…before doing any mods I’d get this issue looked at.
Completely agree. I will get that done tonight. I didn't know you could do that on DFI. Cool trick. I would think I needed to disable the fuel the crank. Maybe I have a weak lifter not pressuring up as well given the variance of oil pressure at low RPM?
Left factory gap at .04 from NGK. Also thought they may possibly be gapped too far. I don't recall the issue changing much if at all after the NGK were installed.
I do have a cheap EVAP smoke canister here to check possible gasket leaks. But unless someone has been in the motor, or broke a plastic line I can't find I am not sure anything else would cause the leak. Not enough miles for the EGR to be plugged all to crap and stuck, same for the EVAP canister.
[QUOTE=Zero1;1608977392]Completely agree. I will get that done tonight. I didn't know you could do that on DFI. Cool trick. I would think I needed to disable the fuel the crank. Maybe I have a weak lifter not pressuring up as well given the variance of oil pressure at low RPM?
Left factory gap at .04 from NGK. Also thought they may possibly be gapped too far. I don't recall the issue changing much if at all after the NGK were installed.
I do have a cheap EVAP smoke canister here to check possible gasket leaks. But unless someone has been in the motor, or broke a plastic line I can't find I am not sure anything else would cause the leak. Not enough miles for the EGR to be plugged all to crap and stuck, same for the EVAP canister.[/QUOTE
Completely agree. I will get that done tonight. I didn't know you could do that on DFI. Cool trick. I would think I needed to disable the fuel the crank. Maybe I have a weak lifter not pressuring up as well given the variance of oil pressure at low RPM?
Left factory gap at .04 from NGK. Also thought they may possibly be gapped too far. I don't recall the issue changing much if at all after the NGK were installed.
I do have a cheap EVAP smoke canister here to check possible gasket leaks. But unless someone has been in the motor, or broke a plastic line I can't find I am not sure anything else would cause the leak. Not enough miles for the EGR to be plugged all to crap and stuck, same for the EVAP canister.[/QUOTE
There is no EGR.
I flooded the car like you said. No abnormailites heard.
Well maybe I have a crap couple plugs. Even new. I will swap them tonight and try a different MAF and see if there are any changes. Plugs I'm going back to are the 41-114 and not touching the gap other than verify the 38-42 Oe gap per the service manual.
May do compression check while I have them all out.
my old HpTuners MPVi do not report the misfire streaming data.
Which one?
I have the MPVI 1 PRO and I can log misfires by each cylinder. Are you sure you're looking at the right channel/sensor?
I'm about on the same boat as you. What you describe is what I had. I removed headers this week and found that LH gasket was installed the wrong way + some leaking. My misfires were all on that same bank (mostly cyl5 but also 1/3/7), no codes. Changing upfront O2 improved my LTFT stability. I also have KN. Don't forget to reset LTFT after you change any component related to intake. My LTFT and STFT are now stabilized
Last edited by mjollnir51; Jul 25, 2025 at 03:41 AM.
These cars do have a little lope to them stock and the HPFP is noisy and with the stock exhaust you can really hear it ticking when a wall is nearby.
As mentioned above, you can log individual cylinder misfire and knock retard. In fact if it's missing you should be able to log spark retard and then look at it in a graph vs RPM (horizontal axis) & Cylinder Airmass (vertical axis). For convenience you could also pick MAP. A miss may not meet the threshold of setting the CEL but the PCM should be addressing it in the background.
Your IAT looks high. I'm in the Dallas area as well. Here's a recent log from mine (416 stroker, big cam, headers, etc). Note the outside temp and the IAT. This is after a 25 minute drive and it's idling in the garage...
Although unusual, I'd make sure all the coil connectors are fully seated. Also use a mechanics stethoscope on each valve cover to listen for a broken valve spring.
Was it like this when you bought it or it just started? Auto or manual transmission?
If you want to post an HP Tuners log, I can take a look at it if you want. Needs to be more than a minute long to really look for anything and I'd add the misfire and knock retard channels among others.
When I got my 2018 Stingray I was told, it's normal. It's a high powered engine, expect some Lope. Several people told me GM enginerred it in, on purpose .
These cars do have a little lope to them stock and the HPFP is noisy and with the stock exhaust you can really hear it ticking when a wall is nearby.
As mentioned above, you can log individual cylinder misfire and knock retard. In fact if it's missing you should be able to log spark retard and then look at it in a graph vs RPM (horizontal axis) & Cylinder Airmass (vertical axis). For convenience you could also pick MAP. A miss may not meet the threshold of setting the CEL but the PCM should be addressing it in the background.
Your IAT looks high. I'm in the Dallas area as well. Here's a recent log from mine (416 stroker, big cam, headers, etc). Note the outside temp and the IAT. This is after a 25 minute drive and it's idling in the garage...
Although unusual, I'd make sure all the coil connectors are fully seated. Also use a mechanics stethoscope on each valve cover to listen for a broken valve spring.
Was it like this when you bought it or it just started? Auto or manual transmission?
If you want to post an HP Tuners log, I can take a look at it if you want. Needs to be more than a minute long to really look for anything and I'd add the misfire and knock retard channels among others.
Has been like this since I bought it. M7 trans.
It has a small limited warranty for the first 4k miles. Took it to shop they are stating the lifter on #7 ex, is the issue. Waiting on warranty approval for all lifter replacement as well as new cam. Unfortunately shop will not go outside OEM. Sure would have been nice to cam it plus some $$$ and most of that one the warranty company. Won't know anything until Tuesday.
I don't know if you actually have a misfire. You have 2 different scanners saying it has no misfire. I know that my 19 Stingray has a rough as he11 idle that I really don't like. If I bring the idle up to 750 w/ my foot it smooths right out. I keep thinking to buy HPTuner to adjust the base idle speed but so far I just live w/ it.
They do have a little bit of a lope at idle. From the factory warm idle is quite low, I bumped both my cold and warm idle up 100 rpm with a diablo tuner. It still has a little lope at warm idle but it's not like it was, bumping the idle up a bit also helped with that dead spot off idle which is a thing with the manuals.
If you are unable to identify the source of the misfire, it is best to take your 2019 Stingray to a Chevrolet dealership for a diagnosis. As they are the experts with all GM vehicles, they will be the best source for assistance. Should you need help connecting with one in your area, feel free to email us at socialmedia@gm.com with your Username and Forum title in the subject line.
I am having an issue where the engine misfires at idle, you can feel it, however there is no MIL. My Icon T8 scanner as well as my old HpTuners MPVi do not report the misfire streaming data. I have not owned the car but a couple weeks 35K miles 2019 Stingray M7. I am at a loss here and I was really hoping you guys can send me in the right direction.
Replaced the plugs with NGK Iridium ix LTR5ix-11, as well as the AC delco spark plug wires with OEM.
I did notice the IAT on the high side 140+ even when idling in driveway for an extended period. Threw this out as the misfire is present just after warmup and IAT are low. Ambient around 90 degrees (Dallas Fort-Worth TX)
Mild exhaust leak, can only really hear it up again a fast food drive through wall. Seems it is at the "collector" on LH side.
Both B1 and B2 02s are oscillating, while my LTFT is -11 to -14.
It seems the misfire is worse after a highway run or long drive. Driveablily really doesn't seem all that affected, other than a couple spots in the lower RPM. Assumming I am really being critical and trying to feel it just out of 1st gear.
The only modification I have found so far is the K&N cold air with box. No codes present even non-Mil.
I got my 2016 Stingray about a month ago. Three days later it threw a code for Random Misfire, which totally bugged me. But I put in Sunoco Super High Test Premium at $5+/gallon and its been running fine since. Maybe for you too?
C7 Base idle misfire
