premium gas caused engine misfire

[putszie]

hello everyone. i am happy to be part of this forum cause i just bought my used 2005 jeep liberty 2 days ago but unfortunately i started to have some issues on it. i have a mechanic friend that helped me to check and see what he thinks about it before i bought it and he says it a good one so the deal was made. he then advised me to use mid grade gas but for now just put a little bit of premium gas, i got quarter tank on a regular gas then i put 19 liters of premium gas then the next morning i started the the engine and the engine light turns on and i started noticing the vibration from the engine that i suspect an engine misfire and so i told my friend and have it check with a scanner device and it shows cylinder 4 misfire. it saddened me cause all my money in my account almost got emptied and now i have this problem that will cause me some bucks to figure out and fix... if anyone knows what exactly we should do without spending that much would be greatly appreciated... thank you all

 

[K9JEEP]

Same thing happened to me a few months ago when I picked up my 07 with 38k miles on it. I replaced all spark plugs and still misfire in cylinder 4. I had compression test done and all checked out ok as well as pressure on the fuel rail. I ended swapping out the number 4 injector and that seemed to have solved my issue.
This vehicle supposedly sat for almost a year before I got it so it could have been a combination of old or foul gas, some build up that caused the issue. I also seafoamed it and used some Marvel's Mystery Oil per everyone's recommendations.

I'd try those easy steps for at before throwing a bunch of money at it.

I've also only been using Shell 87 and its been great so far.

Try driving through a few tanks of regular gas with a fuel cleaner and see how it responds.

Sent from my SM-N920T using Tapatalk

 

[putszie]

thnk u k9 jeep... i will absolutely try your tips

 

[Dave]

Welcome.

Yeah, the KJ requires 87 octane per the owners manual. No need for premium gas.

Dave

 

[BillyG]

After I bought my 07 Liberty, I decided to clean out the fuel system with Gumout Multi-system Tune-up and a half a tank of 91 octane (87 regular and 93 premium around here). I also changed the spark plugs and later that day threw a multi-misfire code. I changed the spark plugs to a different brand and cleaned the coil pack but the code was still there. I took it back to the dealer who then checked everything and determined that the upstream O2 sensor was bad causing the misfire.

Did the Gumout ruin the O2 sensor? I have no idea and neither did the dealer. I think if I ever use anything else, it will probably be just a bottle of Techron.