Surging on cold start

[paul12]

I had my cooling system pressure tested on Monday. The last three mornings when I start the truck, the motor sits there and surges. Any suggestions? Could this be caused by a vacuume line getting bumped or something like that?

 

[paul12]

ttt

 

[Heavy_Metal]

Can someone please tell me what "ttt" means?

 

[paul12]

To The Top

 

[Heavy_Metal]

Check your Idle Air Bypass. They stick quite often and symptoms are like a vaccume leak. Mine does this sometimes too. Go to Ford and get a can of throttle body cleaner.

Also, how long has it been since a tune up! When cold, a poorly tuned Lightning will idle weird when first started.

Just my 2 cents.

 

[Heavy_Metal]

I forgot to add this to the last post.

No, a coolant leak down check will not cause the problem you have. The pressure test consists of a radiator cap with a pump on the end of it.

Did you have anything else looked at? Do you trust your mechanic? Use a can of WD-40 or starter fluid to detect a vacuum leak. Usual spot is behind the vacuum tree behind the upper intake.

Why were you having a pressure test done?

 

[paul12]

Check my other post regarding coolant leak. Possible leak around the intake. I always smell anit freeze.

I didnt have anything else checked out.

Yes i trust the mechanic. Its a fellow L owner on this board. No question in my mind.

Thanks again for the input!:tu:

 

[Brandon Paris]

WHEN YOU SAID IF THE TRUCK IDLE'S FUNNY WHEN YOU FIRST START IT UP ON A COLD MORNING, THEN YOUR TRUCK IS OUT OF TUNE. WELL WHEN I START UP MY TRUCK IT WILL IDLE AT 1500 RPM, AND AFTER A MINUTE IT WILL DROP BACK DOWN TO 1000RPM, IS THIS CONSIDERED WEIRD? OR DOES THIS HAPPEN JUST BECAUSE THE TRUCK'S ENGINE IS EXTREEMLY COLD.
THANKS.-BRANDON-

 

[Lightning Struck]

Brandon, it's normal..It's the cold startup idle in the EEC, kinda like a choke..

 

[Heavy_Metal]

On a cold start, a high idle is normal. After the engine warms up, the idle will drop. A surging idle is not normal. Engine hot or cold! Surging indicates a vacuum leak. Which for most of us will be the Idle Air Bypass problem or a vacuum leak.