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Won't idle

T

Thor 1211

Silver Level Sponsor
My series V with dual Strombergs just won't idle. First I thought it was the carbs. Rebuilt them, adjusted the float height, new diaphrams etc. and synced them. Then the ignition, new Petronix Flamethrower distributor and coil. Made it smoother but when I try to set the idle it will run ok for a few minutes then stumble. If I blip the throttle a couple of times it will idle high (about 1100 rpm) then stumble. I thought of vaccuum leaks so I installed new gaskets between the carb and manifold, plugged the vac ports and tried again. Same deal. The plugs are tan color the timing is spot on. If it was fuel delivery I think I should have a problem when its running hard and not at idle.
The gas is clean, no real dirt in the float bowls.

I don't know if it's related, but when I put in the clutch it seems to make it worse. I'm thinking thats a dragging throw out bearing?

Help!!!
 
RootesRooter

RootesRooter

Donation Time
Is this a sudden change or has the car always refused to idle under 1100?

If no sudden change, do your throttle shafts have noticeable play? Gradual wear of the shafts and/or bushings = constant vacuum leaks and raises the minimum idle.
 
Nickodell

Nickodell

Donation Time
Sounds like a classic vacuum air leak - manifold vacuum is highest at idle, thus sucking in more extra air, and lowest when rotating faster and/or under load - thereby leaning out at idle. If you set the idle speed to about 1500 rpm, does it do the same?

However, the fact that it runs OK for a while at idle before stalling is puzzling.

You might try this. Take off the air cleaners and when it starts to stumble, squirt some diesel start (ether) into each air intake and see if it picks up again. NOTE: Do this outside! If it does, you have confirmed an air leak.
 
R

RootesRacer

Donation Time
Oops! I forgot to consider that the piston slides may be getting hung up.

This "acts" like a vacuum leak in that it causes a lean condition after the piston sticks in a higher position than the diaphragm would like it to run for the air volume at that op point.

If this is the case the jet centralization proc is in order.
 
A

agmason54

Donation Time
Thor
Suckin air...spray intake etc with starting fluid,to find source of suckage. Better yet mash the carbs with your magic hammer and go with a 2 barrel..
Odin
 
J

jimandi

Donation Time
If you have a pvc valve try blocking it off with a plug. My series IV acted the same way, sometimes it would idle great, sometimes lousy. Blocking the pvc helped.
Jim
 
Nickodell

Nickodell

Donation Time
jimandi said:
If you have a pvc valve try blocking it off with a plug. My series IV acted the same way, sometimes it would idle great, sometimes lousy. Blocking the pvc helped.
Jim
Click to expand...

I took Tiger Tom's advice 30 years ago and did away with the PCV valve. No I don't dump crankcase fumes into the atmosphere, I have a tube that leads the "road tube" into the air intake.
 
T

Thor 1211

Silver Level Sponsor
Well, turns out the fuel pump was sucking air and leaking around the bowl and I came upon it purely by accident. I was checking the line to the brake servo when I happend to look down at the fuel line into the pump and saw there was gas around the bowl and on the inlet and outlet. The I saw a bubble come up inside the bowl. So I took it the pump off, cleaned it out and put some teflon tape on the inlet nut and a better clamp on the input hose. Theres a stub of metal pipe on the pump and then a rubber line back. Neither had a very good seal. After a short drive the idle settled to about 1100 (on the tach anyway) without stalling out. Not perfect but better than before.

I had already blocked off the pvc valve when I tried to get rid of any vaccuum leak.

Thanks to all who offered help.
 
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