2011 v6 misfire

[Christok]

Hi everyone. i know this topic has been covered and I went through a lot of the threads but most of them are over 4 years old.

WHen I start my car it misfires. Most of the time I just turn the engine off wait 30 seconds and restart and then it clears itself but recently it does not clear itself until after a few tries. Also if I am driving and accelerate hard it will again go into misfire mode and I have to pull over and stop then restart.

A bit of history, the first time this problem presented itself I had around 34000 km (a little over 20,000 miles),on the engine. It was under warranty so I went to the dealer. They said I had had bad gas and that 3 of the injectors had to be replaced and since it was under warranty and the other injectors were borderline they replaced all 6 injectors. I immediately switched to midgrade gasoline and I added a catch can to the car. That seemed to work but now I have 89,000km on the car and the problems are resurfacing on a regular basis. Over the past 2 years i would get a misfire but only if I was driving and then put the air conditioner on and accelerated .

Now it is happening more frequently, as well as misfiring upon starting up in the morning. GM wants $200 just to connect the reader to the car to see what the codes are. I don.t have that kind of money to spend just to see what the codes are and I certainly don't have $2200 to have the six fuel injectors changed again ( what they would have charged me if the car was not under warranty). I have a reader but it will not give any codes to my reader although in the past it did give a misfire code.

I was just wondering if anything new has come to surface as like I said the old threads are mostly old.

Thanks for any help

[KillboyPowerhead]

You can get a decent reader for well under $200 (I bought an Autel AutoLink AL519 from Amazon for under $100).

FYI, a misfire is determined by the crankshaft sensor. Every time combustion happens in a cylinder the crankshaft is spun, and in the time between two cylinders combusting the crankshaft slows down ever so slightly; if the crank sensor sees that the crankshaft slows down more than normal a misfire is determined (i.e. if one cylinder didn't combust, by the time the next cylinder combusts the shaft will have slowed down more than normal).

Knowing the cylinder or bank on which the misfire is happening is important in fixing the issue. Possible reasons for a misfire include:

Lack of fuel (injector-related, or vacuum leak);
Lack of air (valve stuck closed/broken rocker arm - probably not your case if it's intermittent);
Lack of spark (bad spark plug or injector or cable);
Lack of compression.

[Christok]

Thanks for the info. I do have a reader but now when I connect it it does not give me any readings

[ElderJ]

I'm not a mechanic, so I can't diagnose squat. I do know that I accidentally overfilled my camaro with oil awhile back and caused a misfire. Only happened once and it cleared itself. I pulled the plug and it looked alright, I guess. Hasn't happened again, so I'm good.

[PaulsSS]

20k miles is way low to have injector issues. I'd have to guess you are getting very poor grade fuel. I would only buy premium and use a good injector cleaner every 1k miles. You could also use a injector lubricant every tank full. I've never had a injector problem on the v6 car in over 100k miles. I use Techron every 1k miles and Lucas fuel system lubricant in every tank, always premium because of the extra cleaners in it.

[Rock-It Man]

Lots of possible causes including plugs, coils, the dreaded worn cam chain, but also possibly something as simple as a tired battery on your 2011.

[Christok]

I just put a new battery in it recently but will try some of the cleaners suggested. I also thought that 20k miles was quite unusual to have the injectors changed however it was under warranty so I went along with it. I was thinking that the recent misfire situation upon starting could be due to the colder weather as I am on the East coast of Canada

[Christok]

just an update. I put a can of STP injector cleaner and valve lubricator in a tank of gas then the next tank I put in a bottle of seafoam and now I am adding Lucas with every fill up. SO far the problem has not repeated itself and the check engine light has turned itself off so hopefully this was the problem.

[ElderJ]

Did you ever pull the codes in the system? Not sure if you had a reader or not. Also, try to find you a good mechanic buddy if possible (yeah, I know...). They're worth more than their weight in gold for diagnosing issues on our rides. I can do routine maintenance and brakes, but when crap starts acting funny, I'm a fish out of water.

[Christok]

I tried hooking in my reader but for some strange reason it would not give me any codes. I have a problem with my trunk button and I still have some time left on my extended warranty so I will take it in to the local red seal mechanic here that used to be a mechanic for GM and get him to read any codes at the same time he changes out the trunk button

[Christok]

just an update. I have been using lucas with every fill up and the problem seems to have disappeared. I guess the misfire was due to one or more dirty injector

[PaulsSS]

You are getting very poor grade fuel. It may not be the octane but dirt contaminates in the fuel that end up burning onto the insides of the injectors during heat soak. Every time you shut the car off the injectors get cooked from the internal engine heat. Anything in the fuel cooks to the insides and outsides of the injectors which causes them to jam up not spray properly etc.

[AlanRubin]

Originally Posted by PaulsSS

You are getting very poor grade fuel. It may not be the octane but dirt contaminates in the fuel that end up burning onto the insides of the injectors during heat soak. Every time you shut the car off the injectors get cooked from the internal engine heat. Anything in the fuel cooks to the insides and outsides of the injectors which causes them to jam up not spray properly etc.

Bullshit, and more Bullshit it was running fine, then not. I have 231,000+
miles on mine and I use 87-88 octane fuel, and run 380 miles a day, 3-days a
week. ORIGINAL fuel injectors. Nice guess work...

[PaulsSS]

Hey no reason to get nasty, thats my opinion. Solved his problem for him, its more than you did. Plus you obviously have no idea why injectors get fouled ZERO! Another big problem in these engines is oil usage, it can foul the injector rather quickly. If you are using alot of oil the injectors are going to suffer. The oil deposits on the injectors and every time you shut off heat soak cooks that oil and bakes it on to the injectors. This is the major cause of bad injectors. If you don't believe me ask ANY GM engineer.