: Heat Affecting Idle Speed?



DopeStar 156
06-11-05, 04:17 PM
Now that I reconnected the vacuum line to my carb the car is running normally again but lately, even before this whole fiasco with me damaging the fuel line and everything, ever since we've had this hot humid weather on the East Coast my idle has been lower than usual. I'm thinking the hot humid air going into the carb may be causing the car to run a little lower than usual as I believe cold air provides a better idle with a carb. I dunno, I could be wrong but is that so? Would hot humid air lower an idle?

N0DIH
06-11-05, 07:05 PM
It should idle around 500-550 rpm in drive. Is it lower? Is the ISC kicking in trying to keep the engine from dying? The 307 can idle low with such a mild cam. But it should be a smooth idle at min idle in drive.

I have found the lowest idle you can live with gives a slight more flash stall off the line, and hence better off the line acceleration. I know it isn't much, but the 307 needs all it can get!

DopeStar 156
06-12-05, 12:38 AM
See I dunno what the RPM is since I lack a tachometer. It just seems as if it's idling lower than usual, but no stalling or anything bad like that and it's definately smooth. There's no unusual vibrations. If anything seems different, it's quieter in the drive idle. Also what's the ISC?

N0DIH
06-12-05, 01:59 AM
The ISC is the Idle Speed Control, the thingy that pushes up on the throttle when the vacuum gets too low. You can see it on the drivers side of the carb, has a vacuum line running to it. Disconnect the vacuum line while the engine is running (and in park, hopefully with wheels blocked if you don't trust your tranny!), it will idle up to 1500 to 2000 rpm. This thing is pretty cool, and simple and very effective.

I wish I could hear/see it, but it almost sounds like it is running correctly. Does it drive ok? No drivability issues over it? Like bogging out the hole, or stalling/flashing the converter too much? This should help deceleration too, as well as fuel economy might be slightly improved for the city driving.

DopeStar 156
06-12-05, 11:54 PM
Nop, no complaints about the ride. I'll check the ISC tomorrow morning though. Thanks for the tip.