Rough idle after running at high throttle (1 Viewer)

[Random Dan]

Hello all,
I tried this in the 60 forum but didn't get any help so I figured since it's a 2F I might have better luck here.

My FJ61 has been running for about six months now, but it is having some issues. It is a basic 2F with no smog equipment other than the EGR system. From the factory it had a points dissy but I replaced it with a USA big cap.

Issue: Rough idle
This is kind of a weird one. When it is first started up the idle is pretty good but after running at high throttle it gets really rough. Today when I pulled off the interstate after doing 100-105 for 45min or so it died when I clutched in. It restarted fine though and I left the choke out a bit to keep it idling. After sitting for a couple hours it restarted and idled fine until I drove for a while, at which point it got bad again. I checked the float level while it was running rough and it was halfway in the sight-glass. My next thought was vac leak so I did the carb-cleaner test all around the manifold and vac lines but the idle didn't change. I unhooked the clutch line and put a vac gauge on it got 19 in Hg with no fluctuation

 

[65swb45]

Next time it happens, try taking off the air cleaner and looking inside the carb. What you are looking for is whether there is any fuel dribbling out of the emulsifiers at idle. If so, that would likely be the source of your rough idle.

Mark A.

 

[Random Dan]

Next time it happens, try taking off the air cleaner and looking inside the carb. What you are looking for is whether there is any fuel dribbling out of the emulsifiers at idle. If so, that would likely be the source of your rough idle.

Mark A.

Sorry I'm a little fuzzy on the terminology here. Do you have a picture of what I should be looking at? Are emulsifiers the venturi?

 

[PenguinScotty]

Here is a quick link to Pinheads carb-rebuild video, which should give you an idea of what it is. Perhaps you could call them Venturis or Nozzle, but people who actually know their terminology might get mad

Edit: Ofcourse it didn't post the link, but embedded the video... Please go to 1:50 or so, where he talks about it.

 

[Random Dan]

I looked and didn't see any fuel coming out.

 

[GA Architect]

Mark may be referencing this?

 

[Random Dan]

Ok, so I tried readjusting the idle using the lean drop method as outlined in the 2F repair manual. It idles much smoother now at 20.5 in Hg, even for running 110 down the highway for 8-10 minutes. I will be able to do better testing tomorrow.

I don't know why this worked, because the mixture and speed had not been changed since it was running good before, but it works now so I can't complain. Hopefully it stays that way, otherwise I will be back here.

 

[Random Dan]

It is idling much better now but still gets rough after running for awhile. If I leave it idling for long enough it eventually smooths back out again.

 

[Gotta be Geared]

Do you have the insulation/heat shield between the exhaust manifold and the intake? On mine it had deteriorated and it would heat soak the carb and "vapor lock" (not sure if that is the correct term) but since it sounds like it does it under heavier load when exhaust temps would be high that may be something to consider.

Hope you get it figured out!

 

[Random Dan]

Do you have the insulation/heat shield between the exhaust manifold and the intake? On mine it had deteriorated and it would heat soak the carb and "vapor lock" (not sure if that is the correct term) but since it sounds like it does it under heavier load when exhaust temps would be high that may be something to consider.

Hope you get it figured out!

It never had a heat shield.

 

[Gotta be Geared]

That may be worth looking into, I think the 60's had an insulator and a carb fan to keep them cool and prevent vapor lock. Although you mentioned that it restarts fine, usually a hot carb or vapor locking makes the restart especially hard until it cools a bit.

 

[Random Dan]

That may be worth looking into, I think the 60's had an insulator and a carb fan to keep them cool and prevent vapor lock. Although you mentioned that it restarts fine, usually a hot carb or vapor locking makes the restart especially hard until it cools a bit.

Since it's a JDM it came from the factory without smog equipment or a carb fan.