Hey guys, I have a problem that has been driving me crazy since I got my Vette and I know you are the ones to turn to. I have a '96 LT4 Collector's Edition in which the cruise control does not work, not a big thing but annoying nonetheless. In addition, and even more annoying, since Florida is already starting to warm up again, is the fact that the A/C only blows out the heater and defrost vents. The car has the Auto Climate Control system. I started by checking all the vacuum lines and such and initially found the vacuum tank had a broken nipple and that the line leading to it had been plugged. I replaced the vacuum tank (used) and no luck. If I pull either line off of the cruise servo I don't get any vacuum at all from anywhere. All suggestions are welcome, I'm about to give up and take it somewhere before it gets too hot.

 

Vacuum drives a TON of functions on TPI's (and LT1, 4, 5), which are also'Tuned Port' engines. I would seriously try to get a vacuum routing schematic, before givin'a mechanic licence to go fishin'.

When warmed up, do you get the lopin' idle?

Possibly the reason you get no vacuum when you pull the vacuum servo line, is because the function is disabled below 35 mph. I don't know if the vacuum itself is blocked off by a regulated valve. Follow the vacuum line to the intake and see what's there...

 

1st, your 2 lines going to the servo, small one is vacuum, big one is vent. There will only be vacuum on the small one. You need to trace your vacuum source back and see where it is being lost. That is also the reason (probably) why your vents are at the rest posistion (no vacuum). ATC controls have a programmer that controls blend door and mode door and I think they are actuator controlled (motorized) instead of vacuum. Can' be sure at the house here, would have to check schematics at my shop.