I have a 2016 Sonata hybrid. I spent many months dealing with spark plug misfires. In March my mechanic did a carbon cleaning and that made the problem go away. Unfortunately, today (5 months later) it came back. I got a check engine light and when I checked the code it was a misfire again. Specifically, it was a misfire on cylinder 2 (which is where it always is). I cleared the code and drove the car some more and it didn’t (yet) come back. But, based on the history of this car, my guess is that it will come back and eventually get to the point where it does not go away without some kind of intervention. Two things did happen to the car recently before the misfire. They’re probably not related, but I thought I should mention them. (1) Four days ago my transmission fluid, brake fluid, and coolant were all changed by my mechanic. Not because anything was wrong - just because I’m trying to avoid problems by keeping up with regular maintenance. (2) Two days ago I put gas in my car and for the first time I used Lucas Upper Cylinder Lubricant. I’m concerned that I’m going to start having major problems with this car again. Is there something that I can do that might help me to keep these misfires from coming back?
I’ve used this product for many years to remove carbon deposits from intake runners/valves with great success.
Tester
Could be the gas you bought, and or the additive… How often are you adding additives to the fuel tank and or engine oil??
This was discussed in the thread above and possibly one or two other threads…
Still unanswered questions from the above thread…
Either you (or shop) are installing the wrong spark plugs, which I covered in prior post, or counterfeit and or non dealer parts, or you possibly have an electrical issue…
Maybe your buying cheap gas???
Might be time to find an automotive electrical specialty shop…
Thank you.
I am currently using the correct spark plugs. I get exclusively get my gas at Costco. Is Lucas Upper Cylinder Lubricant not a good choice?
Hopefully from the dealer??
Costco should be fine, might switch to Shell just to see if you have any better luck..
Typically additives are not needed and can cause issues like build up on the valves and combustion chamber area…
If you are running good fuel and doing proper maintenance to the vehicle, you should not need to use additives…
Using a cleaner such as Sea Foam (tank) or Marvel Mystery Oil (oil or tank) or equivalent are needed, but MMO is more for sludge and heavy deposits, whereas Sea Foam seems to work great in the tank for decarbonizing the induction side… Always follow directions for either…