My 2001 5.4l 2 Valve engine would smoke at Cold Start-up for about 20 seconds and then slowly go away, 210,000 miles on the odometer. (true dual exhaust, blue smoke out of driver side tailpipe Only)

I decided to try adding a quart of my trusty Marvel Mystery Oil into the engine oil and drive the truck around fro 100 miles or so.

I took the truck for about a 10 mile drive right after I put in the MMO and then let it sit overnight.
The next morning at cold startup there was NO Blue Smoke at cold start-up.

I have driven the truck the next two mornings... No Blue Smoke on cold start-up the next two mornings either. I have to say... I am quite surprised, Only in that I have never put this MMO into the engine oil before only into the gas tanks. What ever the MMO cleaned inside the engine must have took care of the Blue Smoke at Cold Start-up.

I am Very Happy and Pleasantly Surprised at the outcome!!!

 

It did not clean anything but expanded the rubber seals around the valve stems where the oil was being sucked in.
Oil normally runs down the valve stems during engine operation.
Wear in the valve stem guides and valve stems adds to the leaks on an old engine..

 

So Sludge or Grime doesnt get stuck around/at/on the rubber seals in 210,000 miles?

I understand that the rubber seals could have expanded. It seems to me that there had to have been Some Cleaning in that area as well though?.

Couldnt Grime or Sludge get stuck around those rubber seals over time?

(Just double checking - I know you already said the MMO expanded the rubber seals around the valve stems)

 

UPDATE...

Still..... NO Smoke on cold start up!! Yay

I also changed the oil out and put in Shell Rotella 5w20 Full Synthetic - Running Good - No internal engine noises.

 

Any idea why my 1999 F-250 (similar to F-150) 5.4 liter truck won't idle when cold? It runs great and idles great after I drive it awhile. But it will die while driving when cold since it refuses to idle when cold?

 

When you turn the ignition key to ON, the computer is not seeing the cylinder head temperature signal and or the intake air temperature signal to set the fuel rich and open the Intake air controller.
After the motor warms, the Ox sensors control fuel and the motor no longer needs a rich fuel mixture.
What is the motor temperature when you feel it's fully heated?
Does the motor go into high idle at cold start?
Are there any codes set or CEL dash light on?
Could be the intake air controller is sticking closed until the motor warms up.
Or a combination of any above.

 

Something isn't correct somewhere. All these fuel injected engines will start up cold and run well cold, I have never had one fuel injected engine ever not start up when cold or not run well when cold unless there was some issue.(the engine will run at a higher rpm while cold until the engine warms up).

Simplest things first...
1) check your Intake Air Filter, if it is dirty or even if it is not dirty but been in the intake and driven for over a year it May cause a running issue.
2) Pull the air intake boot/hose off the throttle body and spray throttle body cleaner inside the throttle body, all the areas that you can see, to clean it out. It will smoke for a couple minutes when you re-start the engine until it burns all the grime and fluid out. (Mine was filthy, had a thick amount off black grime everywhere inside where I could see).
3) add some Fuel Additive/Cleaner into the gas tank. (for instance, I put Way More in than the directions say and it has never caused a running problem. I personally will put the large 1 Qt. bottle of MMO to a half tank of gas, that is how I do it But, Do your research, I am just saying how I do this, everyone does things differently, usually with he same results though.

Let us know when you have fixed the cold running issue please Sir.

 

i'm calling the IAC!!!