Builds Car souq pickup (1 Viewer)

[WarDamnEagle]

Usually there is an idle speed adjustment screw that sets the idle speed RPM. There should be a tiny amount of slack in the throttle cable when the linkage rests against the idle speed screw.
If the cable tension is being used to set the idle speed, that may be why your idle speed wanders around.
Maybe your idle speed screw fell out?

No; it's there and yes, I was using the throttle cable to raise the idle as a temporary measure. There is a tiny bit of slack in the throttle cable now that I put it back more or less where it was. Because I was already messing with the cable, it was a lazy way to increase the idle to see if it would help with the stumbling. Once it did I just left it there until I felt like messing with the issue again.

 

[JuanJ]

So just to follow up on this issue and to thank @JuanJ for his advice. The first thing I did was to try to find a vacuum leak with propane using an unlit propane torch. No luck with that technique at any of the vacuum lines. Then I bought some starting fluid and tried again. Still no bueno. I then went down an alternative path and started messing with the throttle cable. I eventually got the engine to not stumble but only by adjusting the cable to where the "idle" rpm was around 1100 or so. Obviously that's a bit high but I left it there and ordered a new throttle cable - just because.

Fast forward more than a month and yesterday I was out driving it for the first time in a while and the high idle at red lights was annoying. So I decided to adjust the cable so that the idle was back to a normal range. My thought was to try again to find a leak and/or convince myself to change the throttle cable. Well I got the idle back to 750 and although it doesn't sound absolutely perfect it's good enough that I can't tell if it's ever idled any smoother. Certainly the tachometer is holding very steady and when I had the issue it was bouncing all over the place and the engine would actually die on me occasionally.

So, not sure what the issue is, or was, but it appears to have corrected itself. Maybe some bad gas?

Hello,

Thank you for your kind words.

750 rpm idle is good enough for the 1FZ engine.

The 1FZ-F engine can be sensitive to accelerator cable tension, even more so in old age.

Once the cable is tight enough, it is a good starting point to chase leaks or tune the carburetor.





Juan