18 Ecoboost Mustang rough startup and white smoke?


New Member
Aug 27, 2018
Pompano Beach, FL
Hey guys, new on here. Sorry if im posting into the wrong area but need help. Currently have a 2018 Ecoboost Mustang with a JMS boostmax tune (plug in tune), intake and an open downpipe. Been running that set up for about 10k miles and car runs like a charm, no CEL. But just recently installed a HKS blow off valve onto the cold side piping. Capped the OEM flange on the hot side and put a resistor plug in place of the stock blow off. Inserted a boost reference adapter behind the throttle body where the stock pcv valve is. All lines are connected perfect with no vacuum leaks. Everything was done and installed correctly. Ran for about a day, then got a CEL. Car ran completly fine. Then about 4 days later. Started the car, and the start up seemed rough along with some white smoke. Not vapor. Not a cold start. As if oil was burning.. Idle was choppy until i gave it throttle then turned normal. White smoke disappears after 10 seconds. Just at initial startup. As if it was bad gas. And has been doing it for a few days now. Idle starts out rough and choppy, but just a blip of throttle and idle becomes normal. Car runs completly fine tho, no power or boost loss. Idle is fine after start up.
Going to get codes read soon,
But what could be causing the startup to be rough?? Is it bad? anyone else have something similar?
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I Bleed Ford Blue

Well-Known Member
Feb 13, 2017
North Olmsted OH
My advice, get rid of all that garbage and put the car back to stock. If you want to sound like a ricer, go buy a freakin honda. That JMS device just modifies the factory signals to get very little gain. Fix your car and then get a real custom tune done on a dyno from someone who knows ecoboost engines. That will gain you a lot more power than JMS junk.

BTW, if you put the blow off valve down stream of the mass air sensor, then you are dumping measured air and that will give you a CEL.
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