Hello! I have a bone stock 04 FXT that the father-in-law that borrowed it and filled up the take for me. He said he put premuim in it. (that was Saturday), now today on the way home from work, the check engine light came on and the cruise control light started flashing. After further interrogation of the father-in-law, he admits of using 89 octane. He said it was about half full when he put 89 in. The gas cap seems tight, (it racheted when i tried to tighten it more.) The tank is currently just under half full. Otherwise it seems to run normal. My question is would that amount of 89 octane cause the CEL to come on? Should I fill it up with 92 (or 110?) and keep driving it for a while to see if the CEL will go away? Thanks!
I'm sure some one can give you a for sure answer. But I think lower octane could cause the issues your seeing.
The conclusive thing here is that your father-in-law will never be driving it again! Edit: I don't know for sure, but I'd guess that if you filled it up with 93 and kept doing that for a while (maybe when it is 3/4 full - top it off with more 93) it would sort itself out? I'd also probably baby it and keep it out of boost. My information could be 100% incorrect. Edit 2: Don't use 110.
I think you need to explain to your father in law that your engine could have, or might actually now be toast. Better to get that across now in case you need to have an uncomfortable conversation in a couple months. I wouldn't drive it until I pulled the code. I'd rather buy a rental so I could drive my happy ass down to the local shop and rent a code reader than drive a turbo that waas just driven (probably hard) with the wrong gas and is now throwing a CEL at me. You're PROBABLY ok if it was bone stock and otherwise running nice. It would be more horrific if you were tuned for "the bleeding edge of 93" as Russ would say...
Pull the cel. If its a misfire on all cylinders than yeah, gas. Top it off with 93 and stay out of boost for the rest of that tank. You could add a gallon or 2 of 100 unleaded (94 and broadway station) or xylene/toluene if you really wanted to. Don't bother with octane booster... it'll take about $50 worth in a full tank to raise it a few points.
You could probably get away with putting in a quarter tank of straight e85 as well. If we are going with basic math here: 16 gallon tank 8 gallons 92 oct 8 gallons 89 oct Your tank octane would be 90.5 octane If you burn a quarter tank of that and fill with e85: 12 gallons 90.5 oct 4 gallons 95 oct your tank octane would then be 91.6 To be safe, I'd baby the engine till the needle went below 3/4 tank and then fill it up with e85. 5-6 gallons of it should get you back into 92 octane range
CEL came back as the knock sensor. So we reset the code and I put 92 in, and well baby it for a while and see how it goes! Thank you everyone!! I do appreciate it!! I'll give a update in a couple of days!
Little over the top I think. CA gets 91 max. Stay out of boost and fill with 93 when you get the chance. You'll be fine.
I thought I could remember the number, but I'm don't know now. The scanner just said the code and knock sensor. If it comes on again, I'll try and have them dig a lil deeper. Thank you!
For future reference, If you're worried about the octane level being low, Just add some 100 octane race gas. They are available year round since a lot of snow mobile uses them. 2nd option or first depending on if you know where a race gas station is; drain the tank. All you need to do is remove the return line and connect a hose to an external fuel tank and let it idle. Takes a little bit of time but will drain. But I don't think your issue with the knock sensor and lower octane fuel are related to each other. The only way I've seen a knock sensor come up is either its not connected or it's bad. Not because it's running with lower octane fuel. It's job is to detect knock and adjust according to what it's programmed to.
Keep an eye out for that code. Don't know your mileage or use, but it's definitely possible that one is (or both are) going out. That's something you should replace quickly is it's kaput. Like Ronnie mentioned, probably completely coincidental.
Its got 136xxx miles on it and its not on the road a lot. More or less the family vehicle. Does it use the same knock sensor in both locations? Because I looked at RockAuto and it just listed one kind. Also, where are they located?
Oh wow... I read O2 sensor. Forget my comment about front/rear. Morries mtka can get you a knock sensor (pn 22060aa111) for around $80 iirc.
Thought I should give an update. Been through 3 tanks of 92 and no CEL so far! Thanks again everyone!
