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My 2014 Stingray Z51 with 60k miles has been throwing a P050D code (rough cold start) almost randomly for about a month and a half now. Originally, I would clear it and it would just go away for a few days but eventually I cleaned out the MAF sensor and that got it to go away for about three weeks, up until two days ago. The other day I got the same P050D code along with a P0300 (random/multiple cylinder misfire). I figured it had something to do with the injectors, and it ran smooth after warming up, so I added some Techron and cleared the codes again. It ran fine yesterday with no codes, however today when leaving to go to work I got a flashing CEL, so I pulled over and read codes P050D and P0304 (cylinder 4 misfire). The CEL stopped flashing after turning the car back on so I ended up just limping it to work and made it with no other issues. Also, the CELs have only ever occurred when the car was fully cold, at least sitting overnight. Any other time after the first cold start of the day, even after hours of sitting, it runs smooth and does not throw any codes. When leaving in the morning, you can now hear the sputtering and spitting of a misfire, but when it's warmed up it runs perfectly fine and does not throw any codes. The dealership can't fit me in until Tuesday, so I will be driving a friends car until then since I daily the vette at the moment, but my question is what should I try before then? I was thinking possibly an injector problem or possibly a bad coil, but has anyone had any similar experiences, and if so, what should I start with?
When I get home from work I'll do that and most likely swap one of the coil packs as well to see if the misfire moves away from cylinder 4, then see what happens in the morning when I start it up. Would a bad coil/plug/wire only show issues when cold and not when warmed up? Thats what's really stumping me on this compared to a regular misfire that constantly occurs, this one only does when the car is completely cold.
Thought I should mention, I also took the car back down to stock and the issue persisted, especially when going back and forth between v4 and v8 mode it would be harsh and burble a lot more than normal. I did have the diablo tune installed before that also disabled DOD/AFM but I doubt that had much to do with it. I reinstalled the stock tune and cleared the CELs, and they still came back by the second startup, which is why I don't think the tune had much, if anything, to do with it at all. The car is at the dealer now and I will update more when they come back with what they find.
Semi-update: As far as the dealership has told me, they have pretty much ruled out the spark plugs, wires, and coils as they all tested good and did not change the misfire at all when moved/tested. They are letting the car cold soak overnight and doing a fuel injector test in the morning. I'll update when they get back to me tomorrow.
I normally…well I always bad mouth dealerships because of their lack of diagnostic skills and this just reinforces my feelings…tell them to READ THEIR TECHNICAL SERVICE BULLETINS !!…if you’re in the Southwest area of Florida you can bring it by but these cold start misfires according to GM are normal…and my diagnostic equipment I use is WAY more advanced than theirs…and they only guess !!…I saw it’s #4 cylinder but you disabled AFM…you should tell them not to charge you for ANY diagnostic time...TSB says they should look at “injector pulse width” during this cold start up but the thing is they don't use a scope to check this...you can ask them about it…if they can’t check it I’ll be able to check that…cold start misfires can also be the result of a blown head gasket and carbon build up on your GDI engine.
@C5 Diag What's your source for TSB's? Is there a website or maybe a .zip of each TSB in PDF form somewhere?
This TSB is from Alldata…if you don’t have a service manual for your car you can get a subscription from Alldata DIY for $19.99 a month and there are yearly and a 3 year plan…if you need service info only once and a while the monthly plan is the best and their wiring diagrams are excellent.
This TSB is from Alldata…if you don’t have a service manual for your car you can get a subscription from Alldata DIY for $19.99 a month and there are yearly and a 3 year plan…if you need service info only once and a while the monthly plan is the best and their wiring diagrams are excellent.
Thanks, I use the service manual for everything, but don't have a TSB resource.
Thanks, I use the service manual for everything, but don't have a TSB resource.
You can try a Google search but for a 2014 there are over 1300 TSB's for that model year alone....for me it's easier to find something on Alldata and just do a keyword search.
You can try a Google search but for a 2014 there are over 1300 TSB's for that model year alone....for me it's easier to find something on Alldata and just do a keyword search.
Bought a 1 year subscription with some discount codes from Slickdeals. Looks good. I'll probably use a webscraper to download everything. Then I can search locally.
I normally…well I always bad mouth dealerships because of their lack of diagnostic skills and this just reinforces my feelings…tell them to READ THEIR TECHNICAL SERVICE BULLETINS !!…if you’re in the Southwest area of Florida you can bring it by but these cold start misfires according to GM are normal…and my diagnostic equipment I use is WAY more advanced than theirs…and they only guess !!…I saw it’s #4 cylinder but you disabled AFM…you should tell them not to charge you for ANY diagnostic time...TSB says they should look at “injector pulse width” during this cold start up but the thing is they don't use a scope to check this...you can ask them about it…if they can’t check it I’ll be able to check that…cold start misfires can also be the result of a blown head gasket and carbon build up on your GDI engine.
I know what this is saying as far as the normal cold start goes, you can definitely feel it normally running rough for the first few 20-30 seconds, however this feels like a full-on misfire that continues after that initial warm up period. It may partially be due to it, but it is definitely something more than any cold start period I have experienced in the past 20k miles of daily driving the car.
I know what this is saying as far as the normal cold start goes, you can definitely feel it normally running rough for the first few 20-30 seconds, however this feels like a full-on misfire that continues after that initial warm up period. It may partially be due to it, but it is definitely something more than any cold start period I have experienced in the past 20k miles of daily driving the car.
Then the dealership will have to dig into the diagnosis a little deeper…fuel, spark, mechanical…is at at the dealership still ??…if not and to possibly rule out something mechanical you can do a “clear flood crank” and listen if the engine cranks smoothly and evenly…you just keep your foot all the way down on the accelerator when trying to start the car…it will only crank over.
Yes, it's still at the dealership or else I would try that. As far as I know they are still testing the injectors, I will give them a call tomorrow and see what they find.
Yes, it's still at the dealership or else I would try that. As far as I know they are still testing the injectors, I will give them a call tomorrow and see what they find.
Ok, thanks !!…you should ask them if they checked those injectors with a scope and see what they say….takes 2 minutes to check an injector with a scope…they may be an injector balance test.
05-18-2023, 02:21 PM
Misfire on cold start
