So here's the story, sorry if its long, but i think the details are important.
So there I was, driving out to do some mountain hiking, so I was driving across a road at an elevation of about 9,000 feet. The road was perfectly straight, and not a soul to be seen, so I decide to see how fast I can go. I get to 143 mph at about 8.5 psi, and I shift into 5th. Instantly, I see a huge cloud of white smoke in my rearview mirror, so i say, "****", and slow down. I drove another 10 miles or so to a gas station, trailing a decent trail of white smoke. Somebody stopped by, said they had a similar problem, and said it was bad gas. Then i got to thinking. We don't need to get into the details of why...but in that gas tank, about an ounce of diesel fuel accidentally got mixed in with a full tank of 91. We thought i could simply flush out the tank, run some seafoam etc, and it'd be fine. About another 3 full tanks, and after seafoam, i noticed that it was shaking quite a bit at idle. seemed smooth after 1500 rpm or so, but idle was rough. Felt like 7 cylinders were firing. This entire time, not a single DTC was thrown. I checked all the spark plugs, and the #4 plug was destroyed, so i replaced them all, thinking that would fix it. No dice. Same thing. Then we let the car idle, and individually pulled off the coil packs. There was a drop in RPM for 6 of the coils, but no change with the other two. So i bought two new coils, didn't fix it. After all that, approx 4 tanks after it started, it finally threw a code, which was P0171, which is system too lean, bank 1. Now i have no clue whats wrong, it still feels like its running on 6 or 7 cylinders. I can't smell any gas in the coolant, so i doubt i blew the head gasket. Nothing is leaking, and it isn't misfiring or anything, its just rough idle below 1500 or so. Any ideas whats wrong? HELP!
So there I was, driving out to do some mountain hiking, so I was driving across a road at an elevation of about 9,000 feet. The road was perfectly straight, and not a soul to be seen, so I decide to see how fast I can go. I get to 143 mph at about 8.5 psi, and I shift into 5th. Instantly, I see a huge cloud of white smoke in my rearview mirror, so i say, "****", and slow down. I drove another 10 miles or so to a gas station, trailing a decent trail of white smoke. Somebody stopped by, said they had a similar problem, and said it was bad gas. Then i got to thinking. We don't need to get into the details of why...but in that gas tank, about an ounce of diesel fuel accidentally got mixed in with a full tank of 91. We thought i could simply flush out the tank, run some seafoam etc, and it'd be fine. About another 3 full tanks, and after seafoam, i noticed that it was shaking quite a bit at idle. seemed smooth after 1500 rpm or so, but idle was rough. Felt like 7 cylinders were firing. This entire time, not a single DTC was thrown. I checked all the spark plugs, and the #4 plug was destroyed, so i replaced them all, thinking that would fix it. No dice. Same thing. Then we let the car idle, and individually pulled off the coil packs. There was a drop in RPM for 6 of the coils, but no change with the other two. So i bought two new coils, didn't fix it. After all that, approx 4 tanks after it started, it finally threw a code, which was P0171, which is system too lean, bank 1. Now i have no clue whats wrong, it still feels like its running on 6 or 7 cylinders. I can't smell any gas in the coolant, so i doubt i blew the head gasket. Nothing is leaking, and it isn't misfiring or anything, its just rough idle below 1500 or so. Any ideas whats wrong? HELP!