My wife has a 2015 IS250 F Sport with 86K. We got gas on Saturday and within 2 miles the car started running rough. Eventually the CEL came on. We stopped and checked the gas cap and it didnt fix it. Went to Advanced Auto and had it scanned and it has misfires on all cylinders and random misfires as well as lean codes for bank 1 and bank 2. The car will not stay running now. Under any load it shuts off. Could this be a product of bad gas or do I have bigger issues? Have already tried cleaning the MAF Sensor. That didnt help. Unplugging it will allow the car to drive though which I thought was interesting. Any help is appreciated. Thanks in advance!

 

Does the car run like normal with it unplugged or still rough. Thats your issue if it runs and drives fine. But Im suspecting the issue is deeper than that. Perhaps bad fuel? Contaminated?

 

Sounds like a major vacuum leak as you have a system-wide lean condition.

You should do a visual inspection of the engine bay and make sure no hoses popped off, clamps popped off etc. Do you have aftermarket intake and all that jazz?

 

No intake. Its completely stock underhood. I will def check everything tonight to make sure nothing has come loose. Thank you!

 

As far as the MAF sensor I was not with the car when it was removed but she says it drove much better. i am going to check that out for myself tonight as well. Appreciate the feedback!

 

If it's like other cars, With the MAF unplugged it'll default to a preset fuel/air mixture (usually on the rich side for safety) whereas the MAF will meter the air coming in and add the right amount of fuel. Too little fuel would cause your car to run rough. So either you got a major vacuum leak where the car is inhaling unmetered air and not dumping the right amount of fuel or you have a faulty maf. The first is more likely. The second would be quite a surprise but parts can fail. Are you under any kind of warranty? I know in California that could qualify under an emissions warranty potentially? for a very long time.

Keep us informed.

 

Update: Even after unplugging the MAF sensor it still ran rough. I inspected for a loose vacuum line somewhere and couldnt find anything obvious. Im thinking I have some bad gas from the fillup we did right before this started happening. I plan to siphon the bad gas out and put a couple gallons of good gas and run a fuel treatment and see if it takes care of everything. Appreciate the help and will update on the status as soon as I can find some time to make it happen.

 

i've had this before but not with a lexus. it ended up being water mixed in with the fuel somehow. i had to empty the tank and do a flush to get it all out. after that all was good.