Light blue smoke

Jcg_3v94 · Nov 12, 2020

So every now and then when i turn my car on for the first time of the day (cold start) it sounds a bit sluggish and when its on light blue smoke comes out and smells like unburnt fuel? 07 mustang gt with duel gt500 fuel pumps

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Dino Dino Bambino · Nov 12, 2020

Sounds like it's running excessively rich on cold start up. What mods do you have? You mentioned dual GT500 fuel pumps so I assume you have forced induction, bigger injectors, and a tune.
Have you pulled any fault codes?

Jcg_3v94 · Nov 12, 2020

Dino Dino Bambino said:
Sounds like it's running excessively rich on cold start up. What mods do you have? You mentioned dual GT500 fuel pumps so I assume you have forced induction, bigger injectors, and a tune.
Have you pulled any fault codes?

Mods are saleen supercharger, 39lb injectors and custom tune. Ive checked and no codes

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Dino Dino Bambino · Nov 12, 2020

Does your engine oil smell of fuel?
You might want to check that all the connections from air filter to throttle body are air tight, and look for any possible vacuum leak.
Blue smoke on cold start up can also be indicative of worn valve stem oil seals causing oil to seep through the valve guides from the crankcase to the combustion chambers. Check your plugs for any oil.

Jcg_3v94 · Nov 12, 2020

Dino Dino Bambino said:
Does your engine oil smell of fuel?
You might want to check that all the connections from air filter to throttle body are air tight, and look for any possible vacuum leak.
Blue smoke on cold start up can also be indicative of worn valve stem oil seals causing oil to seep through the valve guides from the crankcase to the combustion chambers. Check your plugs for any oil.

No fuel smell on oil. I did notice the end of my cold air is the back part is all torn apart so when i clamp it down i have to be careful or else it wont be on right. Plugs have no oil either.

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Dino Dino Bambino · Nov 12, 2020

Sounds like your problem is likely to be unmetered air entering the engine downstream of the MAF sensor.

Shrek427R · Nov 14, 2020

I just noticed the same issue with my car. Changed oil and CAI filter, then went to the road course track for two twenty minute sessions about a week ago. The next day at start up, a small cloud of smoke and the smell of fuel. Similar issues of the original posting member, however my engine oil smells like fuel. No engine noise, no oil consumption, no codes runs strong. Stock everything in my 07 Roush 427R and just have an ECU reflash from Roush along with their CAI. I am planning on installing a Moroso oil separator next week per suggestions of many on our forum.

Jcg_3v94 · Nov 14, 2020

Dino Dino Bambino said:
Sounds like your problem is likely to be unmetered air entering the engine downstream of the MAF sensor.

Maybe have to re tune?

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Dino Dino Bambino · Nov 14, 2020

I'd certainly recommend that you do some datalogging to help troubleshoot the problem. You could then send the datalog file to your tuner who'll then determine whether you actually have a problem or merely need a revised tune.
x2 on installing air oil separators on a forced induction engine.

Pentalab · Nov 14, 2020

Use 100% synthetic eng oil. And an oil separator (catch can).....which goes on the driver's side on 05-10 cars.

Jcg_3v94 · Nov 14, 2020

Pentalab said:
Use 100% synthetic eng oil. And an oil separator (catch can).....which goes on the driver's side on 05-10 cars.

Yea i have both passenger and driver side catch cans

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07 Boss · Nov 15, 2020

When was the last time you changed your plugs?

Jcg_3v94 · Nov 15, 2020

07 Boss said:
When was the last time you changed your plugs?

Prob like couple months ago i cant remember to be honest

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Shrek427R · Nov 18, 2020

To continue and expand on the thread originally posted by jcg_3v94. I just bought the Moroso catch can and will install it later this week along with a Mobil 1 full synthetic oil change with WIX filter.

Dini Dino Bambino mentioned unmetered air entering engine downstream of MAF sensor, will a re-flash or new tune take care of this? Will the catch can remove fuel smell from oil dipstick or does the tune take care of this?

I changed my original plugs to BRISK about 5 years ago at 12,000 miles to avoid the two piece original plug issue. I now have 26,000 on my 07 S197, should plugs be changed again?

Thanks to the original poster and apologies for jacking, adding to your thread, but was so surprised to see someone with a similar issue.

Jcg_3v94 · Nov 18, 2020

Shrek427R said:
To continue and expand on the thread originally posted by jcg_3v94. I just bought the Moroso catch can and will install it later this week along with a Mobil 1 full synthetic oil change with WIX filter.

Dini Dino Bambino mentioned unmetered air entering engine downstream of MAF sensor, will a re-flash or new tune take care of this? Will the catch can remove fuel smell from oil dipstick or does the tune take care of this?

I changed my original plugs to BRISK about 5 years ago at 12,000 miles to avoid the two piece original plug issue. I now have 26,000 on my 07 S197, should plugs be changed again?

Thanks to the original poster and apologies for jacking, adding to your thread, but was so surprised to see someone with a similar issue.

No worries Shrek427r im still trying to get the issue resolved as well, its not all the time with the blue smoke but when it does do it i notice the car starts up a bit weak. Im wondering if one of my fuel pumos is bad since i have 2.

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Forty61 · Nov 18, 2020

Shrek427R said:
Dini Dino Bambino mentioned unmetered air entering engine downstream of MAF sensor, will a re-flash or new tune take care of this? Will the catch can remove fuel smell from oil dipstick or does the tune take care of this?

Both of these issues aren’t resolved with a tune.

By unmetered air he means a leak, gap or opening after the MAF that allows air in to the motor that the sensor doesn’t see, this can’t be tuned out as it’s a mechanical/physical issue. You need to verify there is no air entering the motor that doesn’t pass the MAF.

The catch can will not stop the fuel smell, addressing the other issues will rectify that. The catch can is more of a preventative measure to stop oil entering where you don’t want it.

Lime1Gt · Nov 19, 2020

Try idling your car for 1/2 minute before shutting it down. See if the blue disappears on the next couple of cold starts.

Juice · Nov 19, 2020

Ford has acknowledged cold start smoke and they tell owners to not shut down the car until it is fully warmed up. Ok, whatever.
I believe it has to do with emissions. In an effort to "light off the converters" as fast as possible, the factory calibration adds extra fuel and pulls timing for the initial however-many seconds. This is the root cause IMO.

I can clearly hear the change in engine tone when the pcm comes out of "light the cats up" mode. I have not found any way to disable this in the tune, nor does it bother me enough to worry about it. It seems if I blip the throttle, it comes out of that startup mode. I do get an occasional puff of blue smoke every now and then on startup.

Tony Jestis · Nov 23, 2020

I have noticed my 2009 has done the same thing over the years. I suspected valve seals in the past. With my older Gen 1 Mustangs, this was a clear indicator of valve seal wear. Now I understand this is a "normal" start up. I feel soooo much better.

ShelbySteve · Jan 31, 2021

Noticed my car doing this today. 22k miles but I’ve also been getting an intermittent p0133 code. I have long tubes and haven’t checked the oil for a fuel smell. I did however just start the car to move it to do some yard work. Glad to know it’s a common issue and hopefully no real problems.

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