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  • 2005 - 2014 S-197 Mustang -General/Talk-

Switched to e85 on the 3v and now it won't run right.

  • Thread starter Thread starter jcowdough
  • Start date Start date Aug 24, 2025
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jcowdough

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Aug 1, 2023
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Aug 24, 2025
#1
  • Aug 24, 2025
  • #1
my son has an 09 3v that he's dropped a cam in put on headers and bigger injectors for e85. it ran good on gas, but he paid some guy to redo the tune remotely. the guy keeps saying the ow sensors aren't working. one or the other and that he can't write a tune if they don't work right. he bought new o2 sensors and put them in. dude says one isn't working. swap it out then it's a different one. it's always something. so his car runs like ass cutting out and smelling super rich. I told him he needed a smaller gap to run e85 that maybe the alcohol is blowing his spark out with the factory gap for gas. I told him we could make a data log and see exactly what it's doing or not doing, but he seems to think he knows everything and won't listen to me. says that IDK about anything except old cars. lol. I wanna help him out but he won't let me touch the damn thing. I think the tuner guy just scammed him. what do I need to do to straighten this thing out? he still drives it even though it's screwed up and I don't want to see him blow it up.
 

Noobz347

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Aug 24, 2025
#2
  • Aug 24, 2025
  • #2
It sounds to me like a tuner's nightmare.

Here, they have [some car] with unknown mods and maintenance performed by [who knows] with sensors that aren't working.

On a boosted or high compression application, changing the plug gap might be necessary. Otherwise, it's irrelevant.

At minimum, all of the sensors and wiring need to be [correct]. The two upstream sensors need to work, at minimum. You cannot tune MAF or SD without them.

Ideally, take it to a dyno shop that can assist with troubleshooting and minor repair of EEC and electronics.
 
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