Idle all over

[lalsimmons]

My 82 720 runs great but the idle is all over the place. Sometimes like 2200, then other times 1500, then other times 800 or so. I know it will idle higher when it is started cold (goes between 2200 and 1500), but once warm it seems to go back and forth between 1500 and 800. Sometimes between.

I removed the vac lines (vacuum-line-removal-t556957.html), and my mechanic bypassed the EGR when I had a throttle problem. That is the only work that has been done on the engine.

Is this bad, or cause for concern? I assume it is the carb (and the electric choke?), and I assume the answer is to put a Weber on. But I just am not sure how serious or problematic this is. It only bothers me because it isn't consistent and I worry it is a sign of a problem, or can cause damage.

Thanks.

[PEZi]

There could still be a vac leak. Were the remaining hoses all replaced and holes capped off properly? And have you checked with brake cleaner to see if there was a leak somewhere else like the base of the carb or where the mechanic closed the egr?

[lalsimmons]

I replaced the one line i left... from the carb to the distributor. On both ends of the hard line. I also put caps on everything. i guess there is a chance i didn't get something on far enough.

Is this what you are talking about brake cleaner check? the idle will change:
http://www.youtube.com/watch?v=mYa8rcHeN3A

thanks for the help.

[PEZi]

Yep... if there is a leak somewhere the liquid will fill it up and change the idle temporarily letting you know there is a problem there. Brake cleaner just so happens to be a nice safe liquid for engines.

[lalsimmons]

Thanks, I'll give it a shot. Very helpful. Here is another video for anyone else reading this, with a bit more detail.

http://www.youtube.com/watch?v=9CPqbaSgcok

The more I read here, read elsewhere, and watch videos. I think you are right. The engine still hesitates (after the timing was just done) very occasionally, and the idle is weird. It seems like the two together would be a leak. Or at least start by making sure it isn't a leak before I try other things.

Appreciate the help.

[zlich]

mines having the idle problem but its not all over the place it'll start at 1000 and when I let off the gas it jumps up to 2000