High idle problem- any solution?

[rxw567]

Has anyone found a solution to the high idle speed issue that seems to be plaguing several members here on the 720 forum? I am having the same problem, and even went as far as installing a rebuilt carb, with no luck. All of the items recommended on the forum (vac lines, timing etc.) have been checked and verified... The problem seems to actually get worse as the engine warms up(?!)

Could a worn timing chain or partially blocked catalytic converter be causing this? I'm looking beyond the usual suspects. Any help would be greatly appreciated.

http://s884.photobucket.com/albums/ac47 ... ics002.jpg

[breadbox]

Ooh Shiny carb. Blocked cat is definitely bad. Worn chain guide is audible.

I have heard of motors locking up when they get warm, due to bad bearing but you said just the idle is horrible.

For 720's First step is eliminate Vacuum leaks. Check plugs. Then check timing.

What does it look like under the valve cover?

[flinterman2000]

Neither the cat nor the chain would cause high idle. Usually vacuum leaks, bad carb adjustment or distributor timing causes high idle or erratic idling.

[rxw567]

Thanks for the replies- turns out the throttle cable was out of adjustment. The cable housing that attaches to the bracket on the engine side was at 'full slack' postion so I assumed the thottle was returning to closed position. Apparently there is an adjustment stop on the gas pedal that was preventing the throttle from fully closing.

Anyhow, all this caused an idle speed of 1500-2000 rpm with the idle screw backed out. Still getting the all the bugs worked out, talking about a $1000 craigslist truck here.

[sawyer's720]

so wait, all that was wrong was that the accelerator cable had slack in it?? so you just tightened it to where it opened the carb a little bit? im not sure i understand.

[captainzeros]

If the throttle cable is too tight it's the same as having the pedal depressed a small amount all the time, which would result in a high idle.

[sawyer's720]

oh ok, then that must not be my problem cause the cable doesn't pull on the carb at all.

[rxw567]

The idle speed would not go below 1500-2000 rpm no matter what- even with mixture adjustment turned all the way in and idle screw backed out.

The throttle cable on engine side is adjusted for maximum slack:

http://i884.photobucket.com/albums/ac47 ... s002-1.jpg

Here's a shot of the secret adjustment stop on the gas pedal, for some(?) reason, it was cranked all the way in before:

http://i884.photobucket.com/albums/ac47 ... ics003.jpg

as i was saying, got this truck on CL, not sure what all was done to it... it's a one owner '82 has a factory sunroof, a/c and still has the datsun radio thought it was a decent deal for 1200.

http://i884.photobucket.com/albums/ac47 ... ics009.jpg

http://i884.photobucket.com/albums/ac47 ... ics016.jpg

[synack7350]

man she looks pretty clean, when you said sunroof I expected it to look dorky, but that actually looks pretty nice. You did good for 1200, as long as the heads good. what state are you in? somewhere south I'm thinking that thing doesn't look like its been exposed to salt at all.