Odd minor idle issue, slightly fast until it's not Options

[oakdalecurtis]

76 2.0 FI stock except for Crane ignition. I finally got all parts dialed in, AAR, thermostat, no vac leaks, runs perfectly, just passed smog with best numbers ever. It idles at about 700 rpm after warmup, but sometimes when I get to a stop light and come to a halt, the idle will drop to about 1200 to 1300 and hold there. If I let the clutch out slightly to drop the idle further, the idle will then drop the it's typical 7 to 8 hundred and hold there fine. Any idea why the idle would stop sometimes at this slightly higher speed sometimes? It can't be an air leak or the idle wouldn't go to 7-800 most of the time, nor would slowing it further when it's at 1300 rpm get it back to it's normal idle again. Not a big deal, just curious if the wizards of smart in here have any thoughts on what to look at. Thanks

[boxsterfan]

76 2.0 FI stock except for Crane ignition. I finally got all parts dialed in, AAR, thermostat, no vac leaks, runs perfectly, just passed smog with best numbers ever. It idles at about 700 rpm after warmup, but sometimes when I get to a stop light and come to a halt, the idle will drop to about 1200 to 1300 and hold there. If I let the clutch out slightly to drop the idle further, the idle will then drop the it's typical 7 to 8 hundred and hold there fine. Any idea why the idle would stop sometimes at this slightly higher speed sometimes? It can't be an air leak or the idle wouldn't go to 7-800 most of the time, nor would slowing it further when it's at 1300 rpm get it back to it's normal idle again. Not a big deal, just curious if the wizards of smart in here have any thoughts on what to look at. Thanks

http://members.rennlist.com/pbanders/djetp...htm#Drivability

700-800 rpm seems a bit low? I thought 900-950 rpm was the idle range. You could try adjusting your idle screw a bit to move it up (after the car is all warmed up and idling at your current 700-800 setting). To b honest, not sure which screw the adjustment should be made at...air bleed screw or idle adjust screw on the ECU?

[Dave_Darling]

Air bleed for the idle speed. ECU screw for the idle mixture.

If you're worried, you can double-check the mixture when it sticks versus when it comes all the way down.

You might also inspect the throttle body and the pivot shaft for wear. And the distributor advance might be sticking enough to bump the idle RPM up.

--DD

[Rand]

The fact that you can use the clutch to slow the engine down and the rpms stay down afterwards, makes me think you should check the advance plates in the distributor to be sure they move freely.

[TheCabinetmaker]

I agree with distributor. I'd start with timing it. I can create that problem easily by advancing the timing a few degrees. I too think your idle is low.

[Bob L.]

Any chance the throttle and clutch cables could be binding in the tunnel? Is one of them new?

[oakdalecurtis]

Thanks for the tips. No new cables in 20 years of ownership, timing checked recently, all good. If I open the distributor to check the advance plates, is it ok to spray a little WD40 in there to loosen them up?

[boxsterfan]

I can't comment on the WD40 in the dizzy, but at least try bringing your idle up to 900-1000 rpm. See what happens after that.

[Rand]

WD40 might help, but don't count on it. It tends to get gummy over time, which is probably the exact problem you are having. But it might help in the interim and if it does, you'll have your answer (in which case it should be properly cleaned and lubed).

[einic]

Thanks for the tips. No new cables in 20 years of ownership, timing checked recently, all good. If I open the distributor to check the advance plates, is it ok to spray a little WD40 in there to loosen them up?

Newer use spray oil like wd40 for lubrication. Use engine oil on the distributor. Your supposed to add a drop on the felt in center of the axle each time you replace the contacts. This lubricates the two - piece axle and advance mechanism under the plate.