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Blue Smoke on Cold Start

Kaboom5.0

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Hey guys, this is my first post on here so forgive me if I posted it in the wrong place. However, a few months ago I hit a year of ownership with my 20’ Mustang GT. Because of this, I treated myself to some aftermarket goodies that included AirLift 3P, Corsa headers/Xtreme catback, JLT CAI, and a tune from Lund Racing.

I would say about a week or two after all the parts were installed, professionally I might add, I was leaving work as I noticed a plume of blue smoke trailing me. I quickly pulled over and examined the smoke and genuinely thought my piston rings left chat, but later noticed that all the blue smoke was gone after the car warmed up. I then took it to a shop and had a compression test done where it passed with flying ‘numbers’. Knowing that my motor wasn’t blown, I then took it to Ford where they agreed that there was blue smoke, only on cold starts, and that we should do an oil consumption test, a 3,000 mile consumption test. To me, 3,000 miles was outrageous but because they were working with me though my car was modified and still in the warranty period, I complied. Turns out the SA on the case got fired and now after 4,000 miles, they want me to do another test for 1,000 miles, I’m complying, however, the blue smoke is really beginning to bother me.

As I stated, this only happens on cold start, the compression test passed, the modifications to the car were minimal and to me have no chance of causing an oil issue. I’ve began thinking of repairing it myself or at another shop that isn’t ford but am trying to guess on what it is. In my opinion, I think it is my valve seals, I’ve also read it could have something to do with the PCV system. I’m sort of stumped. Any ideas or opinions are greatly appreciated.

EDIT: figured I’d add the car began the blue smoke after I hit 19.5K miles, currently at ~23,990
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Dave2013M3

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Bad PCV or worn valve guides.
 

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pull the cam covers after driving around and note how high the oil level is. Let it sit overnight and re-observe how much less oil is visible in the valve wells. pull all the plugs and with a strong light scope the pistons and see if you can spot one that is a lot wetter than the others. It's probably just one cylinder that's misbehaving.

Or just buy the $10 PCV and swap that and see if that solves things.
here's a thread (of many?) on it.
https://www.mustang6g.com/forums/threads/pcv-valve-need-help.147512/
 

silverbullet85

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pull the cam covers after driving around and note how high the oil level is. Let it sit overnight and re-observe how much less oil is visible in the valve wells. pull all the plugs and with a strong light scope the pistons and see if you can spot one that is a lot wetter than the others. It's probably just one cylinder that's misbehaving.

Or just buy the $10 PCV and swap that and see if that solves things.
here's a thread (of many?) on it.
https://www.mustang6g.com/forums/threads/pcv-valve-need-help.147512/
A leak down test would be able to confirm if the valves are leaking, pulling the valve covers is unnecessary and very time consuming.
 

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Kaboom5.0

Kaboom5.0

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A leak down test would be able to confirm if the valves are leaking, pulling the valve covers is unnecessary and very time consuming.
I’ll definitely get a leak-down test done after I replace the PCV, I’ll let you know what I find.
 
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Kaboom5.0

Kaboom5.0

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pull the cam covers after driving around and note how high the oil level is. Let it sit overnight and re-observe how much less oil is visible in the valve wells. pull all the plugs and with a strong light scope the pistons and see if you can spot one that is a lot wetter than the others. It's probably just one cylinder that's misbehaving.

Or just buy the $10 PCV and swap that and see if that solves things.
here's a thread (of many?) on it.
https://www.mustang6g.com/forums/threads/pcv-valve-need-help.147512/
Thank you for the suggestion, probably will do a leak-down and go ahead and replace the PCV, thanks for attaching the other thread!
 

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2020 mustang with 20K miles I doubt very much it's the PCV.
OP you sure it's blue smoke, not grayish ? Might be the tune giving to much fuel on startup, washing down the cylinders. Have a (a good) catch can ?
 

blue5.slow

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Hey guys, this is my first post on here so forgive me if I posted it in the wrong place. However, a few months ago I hit a year of ownership with my 20’ Mustang GT. Because of this, I treated myself to some aftermarket goodies that included AirLift 3P, Corsa headers/Xtreme catback, JLT CAI, and a tune from Lund Racing.

I would say about a week or two after all the parts were installed, professionally I might add, I was leaving work as I noticed a plume of blue smoke trailing me. I quickly pulled over and examined the smoke and genuinely thought my piston rings left chat, but later noticed that all the blue smoke was gone after the car warmed up. I then took it to a shop and had a compression test done where it passed with flying ‘numbers’. Knowing that my motor wasn’t blown, I then took it to Ford where they agreed that there was blue smoke, only on cold starts, and that we should do an oil consumption test, a 3,000 mile consumption test. To me, 3,000 miles was outrageous but because they were working with me though my car was modified and still in the warranty period, I complied. Turns out the SA on the case got fired and now after 4,000 miles, they want me to do another test for 1,000 miles, I’m complying, however, the blue smoke is really beginning to bother me.

As I stated, this only happens on cold start, the compression test passed, the modifications to the car were minimal and to me have no chance of causing an oil issue. I’ve began thinking of repairing it myself or at another shop that isn’t ford but am trying to guess on what it is. In my opinion, I think it is my valve seals, I’ve also read it could have something to do with the PCV system. I’m sort of stumped. Any ideas or opinions are greatly appreciated.

EDIT: figured I’d add the car began the blue smoke after I hit 19.5K miles, currently at ~23,990
definitely worn valve guide seals. I have the same issue. It isn't causing any other problems aside from eating a good amount of oil. Just change your oil every 3000 miles
 
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Kaboom5.0

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2020 mustang with 20K miles I doubt very much it's the PCV.
OP you sure it's blue smoke, not grayish ? Might be the tune giving to much fuel on startup, washing down the cylinders. Have a (a good) catch can ?
Believe me when I say that was our first thought. We sent data logs to Lund, at first thinking it was running too rich, Lund disagreed saying everything was in order. In cold conditions, I’ll start the car and there will be grey/white vapor but letting it sit for 5 minutes and revving it reveals blue smoke that lingers. After the car is fully warmed up, it does not show any blue smoke, on occasion I’ll see it at after sitting at a light for a few minutes.
 

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definitely worn valve guide seals. I have the same issue. It isn't causing any other problems aside from eating a good amount of oil. Just change your oil every 3000 miles
Yeah, just embarrassing that a 20K mile block is huffing and puffing blue smoke, considering the car will be boosted in a few months, it’s best we fix all potential issues beforehand.
 

blue5.slow

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Yeah, just embarrassing that a 20K mile block is huffing and puffing blue smoke, considering the car will be boosted in a few months, it’s best we fix all potential issues beforehand.
Don't be. Ive been blowing smoke since 25k. If you are going boost, I'd get those valve guide seals fixed during the install.
 
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Kaboom5.0

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Don't be. Ive been blowing smoke since 25k. If you are going boost, I'd get those valve guide seals fixed during the install.
Exactly what I was thinking, just worried that it ends up not being the seals lmao. Trying to run all possibilities. But thank you for the help!
 

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What were the compression numbers ? How'd the plugs look ? Valve seals tend to foul plugs quickly. Worse case is the cylinders took on a 'barrel' shape. narrow top and bottom fat in the middle kinda thing.
 
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Kaboom5.0

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What were the compression numbers ? How'd the plugs look ? Valve seals tend to foul plugs quickly. Worse case is the cylinders took on a 'barrel' shape. narrow top and bottom fat in the middle kinda thing.
To be quite honest I forgot the compression numbers, I vividly remember only one cylinder being about 3-5 PSI lower than the rest. However, check out these plugs.

F8A3A038-A6A9-410A-8E32-692D6BB312F0.webp
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