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Idle speed

Garagetoyz

Well-known member
Joined
Sep 20, 2005
Messages
53
Location
New Jersey
Corvette
78 Silver Anniversary 4 spd Crate engine
Hello all..I have a 1978 with a crate motor. Recently the car has been sluggish off and on and I have not noticed anything wrong until today. When the headlights come up I noticed the idle goes down to 400 and jumps around instead of the usual steady 800. Is this a vacuum leak and would it make the car sluggish upon accelaration ? Any thoughts or info is appreciated greatly. Thx
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
Good guess

Toyz,

I'll say that you have a pretty good guess. Especially if it stays at around 400 while the lights are out (up). Usually, the best way to check the hoses on these is to use a vacuum gauge. Once you have isolated the hoses, and if you found nothing significant, then perhaps the light actuator seals are bad (this is very common).

The seals are available in alot of places. And a set of seals cost around $30 - $45 depending on the company. This condition is robbing you gas milage, so you're better-off in fixing it soon.

GerryLP:cool
 

srs244

Well-known member
Joined
Apr 1, 2005
Messages
462
Location
the deep south
Corvette
1978 pace car, 04 CE convert
i would also suggest that if you haven't ever changed the vacuum hoses in the system, you might want to consider doing that regardless of what you find. the hose kit (i suggest the one dr rebuild sells) is pretty easy to install and could be the best $50.00 you spend. one of the problems that the system has is the deterioration of the hoses themselves allowing "seepage" through the micro cracks you can't even see, making repair a real frustrating situation. you might also want to check each of the hoses where it seats on a fitting. the ends have a tendency to dry out and crack creating problems.

if you decide to restore the system, i would also suggest that you replace the check valve and filter in the system. they are located in the main vacuum line roughly behind the distributor.

the most simple way to inspect and replace the accordian boot and the seal on the actuators if that becomes ncecessary is through the front grill openings after removing the grills. you don't need to remove anything but the grills to make the inspection of both the boot (which you can pull forward to inspect the seal). if they need to be replaced, they can be replaced with the actuators in place by simply removing the clevis pin, unscrewing the clevis itself and removing the old boot and seal and replacing them. there are a lot of threads here on the headlight system, repair, and replacement. just do a search using that as the keyword..

hope some of that might help you a bit.
 

Garagetoyz

Well-known member
Joined
Sep 20, 2005
Messages
53
Location
New Jersey
Corvette
78 Silver Anniversary 4 spd Crate engine
Thank you for the helpful information.I was out in the garage today checking out the replies here..I found 3 broken vacuum lines and it was right where you guys directed me to. I'm sure that as I go along in the system I will find more, but heres a big thx for the help. Cheers! |_|}
 

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