Gray smoke?

AL MC

MEMBER
1999 FORD F-150
4.6L
V8
2WD
AUTOMATIC
120,000 MILES

Every now and then, when I start my truck look I will get a big puff of gray smoke out of the exhaust. It doesn't do it all of the time. I have taken it to an auto mechanic and they kept it for a few days and drove it a number of times but they say it never smoked ounce, I got it back and the next morning a big cloud in of gray smoke came out. Can you tell me what it could be?

5 Replies

JACOBANDNICKOLAS

MECHANIC
108,286 POSTS

Hi,

Gray smoke is usually an indication of a rich fuel mixture. When this happens, does the exhaust have a stronger odor or fuel-like smell?

Also, when you had it at the shop, did they check the fuel pressure to make sure it was within the manufacturer's specifications? If not, check that to see if it is too high.

Here is a link that explains how it's done:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

You will need a fuel pressure gauge, but most parts stores will lend one to you.

Let me know if this is the only issue you are having and if the check engine light has ever stayed on while driving.

Take care,

Joe

SPONSORED LINKS

Was this

answer

helpful?

Yes

No

Sunday, September 17th, 2023 AT 9:19 PM

AL MC

MEMBER
10 POSTS

Could it be valve seals that are leaking? Because I drove it 100 miles and back and I didn't get any smoke when I started it up one time after that for almost a week and all of the sudden one morning, I started it, and a big puff of grayish white smoke came out of the exhaust.

Was this

answer

helpful?

Yes

No

Wednesday, October 4th, 2023 AT 1:50 PM

JACOBANDNICKOLAS

MECHANIC
108,286 POSTS

Hi,

As far as valve seals are concerned, if they were faulty and allowing oil to bypass them while the engine isn't running, the smoke would be blue.

Gray smoke is usually an indicator of excessive fuel getting into the combustion chamber. White usually results from engine coolant being burnt in the engine.

Were you able to check the fuel pressure and fuel pressure drop-off? You could have a weak injector that slowly drains off the pressure.

Let me know.

Joe

Was this

answer

helpful?

Yes

No

+2

Wednesday, October 4th, 2023 AT 5:30 PM

AL MC

MEMBER
10 POSTS

Thank you, Joe, yes, I ask the mechanic if they checked the fuel pressure to Ford specs and they said they did. I am starting to wonder if I know the difference between grayish white smoke and blue smoke. I know when it is black smoke but is there that much difference between grayish white and blue smoke?
When I bought the truck back in 2006 and it only had 67,000 miles on the original engine I started having some smoke come out of the exhaust every once in awhile and I started adding Reslone to my oil changes and it went away but the smoke I am seeing now is a lot heavier and more often but it is driving me nuts because like I mentioned before I drove it 200 miles to the desert and back and it seemed to go away for a week but started in again.

Was this

answer

helpful?

Yes

No

Saturday, October 7th, 2023 AT 12:17 AM

JACOBANDNICKOLAS

MECHANIC
108,286 POSTS

Hi,

If the smoke is from oil, usually you can tell by the smell, even if the color is hard to identify. Is it possible for you to videotape the smoke and upload it for me to see? Via a picture, it could throw me off, but it's worth a try.

Let me know.

Joe