surging at idle
Posting Guru
Joined: Jan 2000
Posts: 1,899
Likes: 1
From: Cullman Alabama
surging at idle
I"m sticking my neck our here. There's so many experts on this site.
Put the Vacuam Guage, the Timing light, and the Tach/Dwell meter ALL on at the same time.
Use a squirt can of motor oil, and a Spray can of Carb cleaner to spray around and see what causes a change.
I would look for a mechanical problem in the Distrubuter. Use a timing light to see if the flash is moving a few degrees.
ALso a little too much fuel can do the same thing. A Leak in the Power Valve gasket, Heck for that matter a leak just about anywhere in the Vacuam system might cause a lope.
A tight Valve, especially an intake valve as well.
Put the Vacuam Guage, the Timing light, and the Tach/Dwell meter ALL on at the same time.
Use a squirt can of motor oil, and a Spray can of Carb cleaner to spray around and see what causes a change.
I would look for a mechanical problem in the Distrubuter. Use a timing light to see if the flash is moving a few degrees.
ALso a little too much fuel can do the same thing. A Leak in the Power Valve gasket, Heck for that matter a leak just about anywhere in the Vacuam system might cause a lope.
A tight Valve, especially an intake valve as well.
Elder User
Joined: Sep 2000
Posts: 718
Likes: 0
From: Golden ,CO USA
surging at idle
my neigbor had a vacume leak and he found it useing a propane tortch. noo not a lit one. he just had the bottle open a little bit so it was letting gas out. he ran it along all of the vacume lines and found the leak when the engine rpm's speed up. the propane burns more better causeing idle to raise. from what i hear this works very good for finding a vacume leak. several of my other buddies have tried this and it works.
'75 F-100 4x4, 4" lift
16x38.5x15 super swamper TSL
390 w/ cam,headers,
and 4 barrell edelbrock
TRIED TRUE and FORD BLUE
'75 F-100 4x4, 4" lift
16x38.5x15 super swamper TSL
390 w/ cam,headers,
and 4 barrell edelbrock
TRIED TRUE and FORD BLUE
Senior User
Joined: Feb 2001
Posts: 180
Likes: 0
From: Powell RIver Canada
surging at idle
I had the same problem with my 351 C in my 78 F-100. it had a REALLY bad fluctuating idle, it ran ok when revved up, but it lacked power under load. I couldn't for the life of me figure it out. My buddy figured it out to be my carb gasket, it's a really simple and stupid thing but worth checking out.
