Cant hold idle when warmed-up?

[Dijon40]

Proud new owners of a 77 FJ40 are having issue with holding an idle when clutch in or coming to a stop. Works fine for about 15 minutes of driving after cold start -then. Checked vacuum line, adjusted carb - really no changes very consistent on ability to run fine for many minutes then it just will not hold. If we work the choke during this troubling period by pulling out interior choke lever as we come to a stop - it will hold idle. Then when you take off depress the choke in and it will work fine - a bit too much work.

 

[Coolerman]

Welcome to MUD!

There is an idle solenoid on the back side of the carb that has to have +12V all while the key is on. This solenoid will help maintain idle. If it has lost it's connection, it will not engage, and the truck will not idle. A quick check: Put your ear next to the carb, and have someone turn the key off and on. You should hear a click as the solenoid engages. If no click, then check the connections for this solenoid. There is usually a green plug connector on the carb. Unplug this connector and check for +12V on the wire NOT connected to the carb idle solenoid wire when the key is on. No +12V? Trace the wire out and see where it is broken.

 

[Dijon40]

After market Holley

sweet I'll check that - thanks so much for additional hope, even if that aint it.
Ill post if it is...

 

[Coolerman]

After market Holley? No idle solenoid on that...

Time to find someone who knows holleys to help you...

 

[Dijon40]

Right, talked to another guy in the neighborhood who had a restored 74 and he wasnt found of the his parts and went back to original equipment - On to 1(800)Holley

 

[Pin_Head]

Idle problems are often related to a manifold vacuum leak.

 

[Dijon40]

manifolds and temperature

so when things are warm things expand and leaks are more prevelant?
Is there any kind of graphite spray that would show sucking action if you sprayed an airborn cloud around - not having any diagnosis equipment. How else to confirm manifold vacuum leak. checked hose to carb -no cracks or leaks?

 

[F-junker]

You most likely have a vacuum leak. you can test this with a variety of methods, some prefered some not. I've used starter fluid and also a propane torch (not lit of course). Check around the base of the carb, the intake surface (a common area) and other vac operated devices. If the engine idle increases while testing around an area, you've found a leak. another possible problem can be your brake booster leaking.

 

[Dijon40]

It does seem to be the mix, but only when its good an warm - Ill try your technique.