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Blue smoke vs gray smoke - oil vs fuel

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Blue smoke vs gray smoke - oil vs fuel

 
Old 02-01-2018, 04:21 AM
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PCV ok? Doesn't sound like you're burning much oil. O2 sensor? What you're describing can also happen if you install the seals backwards, you cannot put the intake seals on the exhaust side and vice versa as the valve stems are different diameters. The exhaust valves are smaller than the intake valves, and naturally are more prone to guide play as a result.
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Old 02-01-2018, 08:27 AM
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Originally Posted by Lovetodrive2000 View Post
OK.... I use maybe a qt every 3k miles if that.

Valve guide seals were replaced, no difference in amount of smoke... was still blue.

Here is the big question....

Why did the color of the smoke change when I went to a heavier oil?

Blue smoke is oil, grey is fuel, white is antifreeze.

So why would the color of the smoke change after adding the heavier oil?

Just to keep this up to date... finally got the car out today, the different injectors or MAP sensor did not help. Still bowing grey smoke after engine braking, and accelerating gently....
First of all, I wouldn't totally trust the more finite art of distinguishing the color smoke from bluish to whitish, especially if you aren't actually seeing it yourself, but relying on a friend behind you. That said, if its indeed whitish and your not burning coolant or emitting steam from a cold morning, then there is really only one other thing it can be and that's blowing unburnt fuel, and that can happen because of either a bad tune(not applicable in your case being oem) or because of incomplete combustion from either low compression in one or a couple of your cylinders, or possibly poor spark in one or a couple cylinders.

You still didn't answer my question on if the valve guides were replaced along with your valve seals? its not uncommon for the guides on these F20 to wear out, especially at 160k mark. Id almost guarantee you put good seals on bad guides and did virtually nothing to help.

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Old 02-02-2018, 02:14 AM
  #13  
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Originally Posted by s2000Junky View Post
First of all, I wouldn't totally trust the more finite art of distinguishing the color smoke from bluish to whitish, especially if you aren't actually seeing it yourself, but relying on a friend behind you. That said, if its indeed whitish and your not burning coolant or emitting steam from a cold morning, then there is really only one other thing it can be and that's blowing unburnt fuel, and that can happen because of either a bad tune(not applicable in your case being oem) or because of incomplete combustion from either low compression in one or a couple of your cylinders, or possibly poor spark in one or a couple cylinders.

You still didn't answer my question on if the valve guides were replaced along with your valve seals? its not uncommon for the guides on these F20 to wear out, especially at 160k mark. Id almost guarantee you put good seals on bad guides and did virtually nothing to help.
I trust the guy behind me as to the color (grey, not white) of the smoke... he has seen it for 2+ years.

No coolant being burnt.... never is low on antifreeze.

Just the valve guide seals were replaced.

Compression is ok... Recent compression test was 205/195/210/205. Leakdown test was done last year, 3%-5%...

And I ask again, why the blue to grey change? What would cause me to blow grey smoke after engine braking?
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Old 02-02-2018, 08:35 AM
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Originally Posted by Lovetodrive2000 View Post
I trust the guy behind me as to the color (grey, not white) of the smoke... he has seen it for 2+ years.

No coolant being burnt.... never is low on antifreeze.

Just the valve guide seals were replaced.

Compression is ok... Recent compression test was 205/195/210/205. Leakdown test was done last year, 3%-5%...

And I ask again, why the blue to grey change? What would cause me to blow grey smoke after engine braking?
Couldn't tell you, other then the thicker oil has reduced some oil burning, and you are now just seeing unburnt fuel. The 195 is a bit low and probably a sizable part of the burning issue, but If the car is using 1 quart every 3k and it has 160k on the clock, Id say your motor is generally fine and just showing some age. Again, continue to drive it and don't worry about it until the oil usage gets to a place where its ridiculous. Maybe in another 50-80k miles, who knows. There are some F engines with over 300k on them.
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Old 02-11-2018, 04:57 PM
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No person can obviously diagnose your issue over the internet, but here is some information based on what I've experienced in the past. I had similar smoke coming out of my exhaust, someone behind my car at the Dragon commented on it and I also noticed it once when backing up quickly into a parking lot. But my car always ran great and never had any oil or fuel issues.

The smoke was only noticeable when I was running a berk HFC, once I swapped back to the oem cat converter it went away immediately. My guess is if you have a HFC or test pipe then you may see that kind of smoke at times. The OEM cat converts hydrocarbons from unburned fuel to water or other non-noxious gasses, the berk HFC is not a three way cat and it doesn't convert hydrocarbons, and a test pipe won't convert anything. I am not sure if you have an oem cat, HFC, or a test pipe, but if you don't have an oem cat then I think your engine is probably running fine and this is not an issue, perhaps with just some unburnt fuel going out the tailpipe. Your oil consumption is decent and your leakdown test is good.

After I installed an air-fuel ratio gauge I also noticed that my car would go full rich for a brief second at very low rpms as I got on the gas from coast or idle situation or engine braking condition, and that was the point where the smoke would show up in the exhaust. At idle or coast or during engine braking the a/f would be around 14.7, then as I got onto the gas pedal it would spike rich very briefly between idle and say 1500 rpms for a brief second, then it would stabilize back to normal readings as I continued to accelerate. I am not sure what caused the rich reading for the brief period of time but I assumed it was a normal condition in the fuel delivery system, still very safe and not a cause of any engine issue, and the extra fuel just shows up as greyish smoke when running an HFC or straight pipe. .

Last edited by zeroptzero; 02-11-2018 at 06:08 PM.
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Old 02-17-2018, 12:06 PM
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Originally Posted by zeroptzero View Post
No person can obviously diagnose your issue over the internet, but here is some information based on what I've experienced in the past. I had similar smoke coming out of my exhaust, someone behind my car at the Dragon commented on it and I also noticed it once when backing up quickly into a parking lot. But my car always ran great and never had any oil or fuel issues.

The smoke was only noticeable when I was running a berk HFC, once I swapped back to the oem cat converter it went away immediately. My guess is if you have a HFC or test pipe then you may see that kind of smoke at times. The OEM cat converts hydrocarbons from unburned fuel to water or other non-noxious gasses, the berk HFC is not a three way cat and it doesn't convert hydrocarbons, and a test pipe won't convert anything. I am not sure if you have an oem cat, HFC, or a test pipe, but if you don't have an oem cat then I think your engine is probably running fine and this is not an issue, perhaps with just some unburnt fuel going out the tailpipe. Your oil consumption is decent and your leakdown test is good.

After I installed an air-fuel ratio gauge I also noticed that my car would go full rich for a brief second at very low rpms as I got on the gas from coast or idle situation or engine braking condition, and that was the point where the smoke would show up in the exhaust. At idle or coast or during engine braking the a/f would be around 14.7, then as I got onto the gas pedal it would spike rich very briefly between idle and say 1500 rpms for a brief second, then it would stabilize back to normal readings as I continued to accelerate. I am not sure what caused the rich reading for the brief period of time but I assumed it was a normal condition in the fuel delivery system, still very safe and not a cause of any engine issue, and the extra fuel just shows up as greyish smoke when running an HFC or straight pipe. .
Hmmm.... interesting.

I do have a Berk HF cat on. For some reason, can't find when I put it on, in my maintenance log.

Maybe I'll have to try and find a OEM cat and try it.

Just installed a Supra PCV valve, which was suggested by another Canadian..

If this doesn't work, I'll try the OEM cat.
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Old 02-17-2018, 05:11 PM
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yeah see how the new pcv works, I think it is more than likely unburned fuel rather than oil, l, but see if things improve or not. An oem cat will help since it will convert the hydrocarbons, but I prefer the performance of the berk hfc so if I'd keep running that after you decide to test out an oem cat. It's not an engine issue it is just that the oem cat will better convert the hydrocarbons and make it less noticeable out the tailpipe, the engine will still run the same with either cat, the oem cat just better deals with the hydrocarbons. .

If it is fuel all you can do is make sure that your plugs (plug gaps), and coils are fresh so that you are burning as much of the air-fuel mixture as possible. I always ran a bottle of Redline fuel injector cleaner once per year (one bottle treated 2 fuel tanks) , which I would recommend to keep injectors performing their max maintaining proper spray patterns. Redline is one of the few products actually strong enough to work with one treatment which contains PEA for maximum effectiveness. Good luck bud !

Last edited by zeroptzero; 02-17-2018 at 05:42 PM.
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Old 02-20-2018, 09:46 AM
  #18  
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Put in the Supra pcv, and changed the oil to get rid of the 15w50 oil.

Took it for a drive with the better half following.

Last time we did this, the first time I engine braked, she saw smoke, this time, she did not.

Drove it around for a bit, and she did definitely saw gray smoke once, and maybe a second time, out of 15-20 attempts.

I guess I'll wait until the Leprechaun run when hopefully Greg will be behind me to watch....

Keeping my fingers crossed!
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Old 02-20-2018, 01:27 PM
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what was your reason for changing the valve seals? and any information about why the guides were not changed? can we confirm no installation error on the seals, does the smoke occur after the seals were changed?

maybe it's the valve guides.

if you think it is fuel, how is your gas mileage?
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Old 02-20-2018, 03:41 PM
  #20  
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Originally Posted by jyeung528 View Post
what was your reason for changing the valve seals? and any information about why the guides were not changed? can we confirm no installation error on the seals, does the smoke occur after the seals were changed?

maybe it's the valve guides.

if you think it is fuel, how is your gas mileage?
Local shop that is well known for S2000 and NSX work, thought it was the valve guide seals. Smoke still occurs after seals replaced.

Since the smoke is now grey, thinking it is not an oil issue.

Seems like I need to stop for gas at the same time as everyone else, and I am running gears (4.44) so I should use more than everyone else.
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