hey guys, got a 07 escalade with the 6.2l v8. its got 335,000km on it and has been running great, never had any engine issues other then the piston slap and noisy lifters


so i have noticed that over the past 50,000 km the truck has had this problem but back in the day it would only do it if i let the truck idle for 4-5 minutes (which i rarely would ever do) and it just gradullay got worse and worse and now it "misfires" at idle within 15 seconds




so the thing is whenever i come to a stoplight and stay stopped for like 15-20 seconds, ill get the message that says " stabilitrak off service traction control" and then the tone of the engine will change and i guess it will sound rougher with a shake, but right when i start driving agian it goes back to normal and then message clears. if i go on the highway, it drives perfect, smooth, good power good revs and never triggers a messsage or anything, but when i come a stop light or any stop, if i wait long enough it will do its thing again.. rough idle, stabilitrak message, and also if i wait like a minute or 2, then the check engine light starts flashing as well, i believe this is because the truck thinks its misfiring or is misfiring and thats why the check engine light flashes.


firstly, the codes i get are p0308 so i know there is a misfire
P0036 HEATER CONTROL CIRCUIT BANK 1 SENSOR 2
P0056 HEATER CONTROL CIRCUIT BANK 2 SENSOR 2
P0449 EVAP EMISSION SYSTEM VENT VALVE/SOLENOID CIRCUIT
P0452 EVAP PRESSURE SENSOR/SWITCH LOW
P0308 ENGINE MISFIRE CYLINDER 8




i also do have some evap codes but have had those forever


so im not a mechanic on my own but i swapped coils and tried to see if the misfire stops and it doesnt. i also swapped the plugs and wires around and still has the same problem. the plugs and wires are relatively new only 50,000 km on them. i used my code reader and traced it as a p0308 so i swapped a brand new spark plug into that cylinder and still has the same problem. but have showed it to a local indie mechanic and he did a leakdown test got 6% so he said the engine is still strong, he said compression test was above 200+ for all cylinders, lastly i believe he said he changed the intake manifold gasket but it still has the same problem. i am assuming he checked the fuel injectors but if not, i guess thats the first thing i should try?




anyone have any luck? i was reading more and someone said when the engines get gunked up and old, the vvt goes wonky and ends up causing this? but not sure if thats the truth

 

When you watch live data does it show a lot of misfires on particular cylinders or do you just feel it idle rough? I recommend watching live data and see if you're getting a lot of misfires on particular cylinder such as number eight or all or some of them.

Where did you get your spark plugs from? Was it an online store like Amazon or ebay or was it a local parts store? Amazon and eBay are overrun with counterfeit spark plugs and wires so you have to be careful. My iridium spark plugs turned out to be counterfeit. After 15 thousand miles the iridium tips were worn down to a nub.

I'd recommend watching your long-term fuel trim numbers. This can be very useful in determining if there is a vacuum leak somewhere. You can watch the live data and then spray brake cleaner or starter fluid around the intake area and if you see the long-term fuel trim start to dip you found your leak. You have to be careful because it's a flammable fluid. there are a couple of excellent videos on YouTube that show how to locate such a problem.

Also check the wiring to the ignition coil and the injector for the number 8 cylinder to make sure it's not damaged or frayed somewhere.

It's going to be a bit more work but you can also try swapping your fuel injectors and see if that moves the problem to another cylinder.

Those O2 sensor related codes could also be part of it but they may just be a symptom caused by the misfire. Not sure how many miles you have in those but it may be time to change them out too.

 

i actually havent been checking live data, i will for sure check all of that thanks!
spark plugs from amazon and also a local auto parts store so they should be good!
i will check the vacuum leak beause alot of people think its that!

never done injectors before, but i guess that will probably have to be one of the first things i try!

 

Update?
I just bought a 2007 Chevy Tahoe as a daily driver/project suv. Its a 5.3 vortec v8 and has 170,000 miles on it . It runs and looks amazing, but a engine light on a pretty vehicle really bothers me.
The codes are for a cyl 8 misfire (P0308)and evap solenoid (idk the code off the top of my head).
I was mostly worried about the misfire because its an actually engine issue so I swapped the coils plugs and wires and the code didn't move. I then replaced them all. The code is still there.
Did you happen to fix the issue? Do you know if the evap is related to the misfire?