MetalEd

I am pretty sure I have a vacuum leak. When I start my car in the morning, it is hard to start. If I put it in gear before it really warms up (3-5 minutes) then it will shake violently and die out. (If it dies out from being put in gear too soon, then it is next to impossible to get it started for the next half hour ... maybe flooded?)
Since it is a 170, I only have a few vacuum lines. The pcv line, the line leading to the transmission and the alternator's vacuum advance line (single) (as well as auto choke). No brake or anything else.
But since this problem goes away once the car is warm and won't come back till the next day, I am having a real hard time trying to locate it. Is there a trick I can use to help me locate it before starting the car? Isolate it to one of the 3 vacuum lines?? Does the fact that it is not a problem when the car is warm help locate it?
Thanks for any suggestions.

cheapstang68

Its hard to find it unless the car is warm, but they do sell vacuum line testers at the local parts store. warm soapy water is the cheaper way of doing it. Butif you only have three lines, why not replace them all?

Iskwezm

doesnt sound like a vacume leak.When running spray some car cleaner around the intake,vac lines etc.If the idle goes up, you found your leak

MetalEd

I just found a vacuum leak right at the intake manifold. The vacuum line that goes to the C4 Auto transmission. I sprayed some carb cleaner on the brass fitting and it caused my car to almost stall out when it is idling in park. this is repeatable, just a little shot of carb cleaner and the car stalls out till barely kept alive.
Could this be what is causing my car to stall out when I put it in gear while the engine is cold? It is such a small leak and the brass heating up as the car warms may just expand just to seal up the vacuum leak. (I won't know if it is fixed till tomorrow or even the next cool morning).

Jonk67

Why not eliminate it with a wrap of pipe tape? I agree with above, with so few rubber vacuum lines replace them all if they're not new, don't forget the one at the rear of the trans modulator.

Your vacuum advance on the dist. can also be a source of vacuum leak. If you pop the dist. cap off and pull the vacuum line from the carb, suck on it hard as you can, you should see the arm of the vacuum adv. pull into the canister. If it doesn't move the diaphragm in the dist. adv. is shot after 40+ yrs., pretty common. With the dist. number (stamped on side) you can get a replacement vac. adv.

I'd also verify that your choke is closed before starting and that it opens fully once the engine is at operarting temp. If it's sticking sometimes carb spray on the linkage followed by lubricant will free it up.
Jon