Yes, it now starts when warm. YAHOO!!!! Question, I have it idoling around 850 (it jumps btween 830-860) in park. When I put it in drive (tires are off the ground) and don't apply the brakes it still idols around 850. When I apply the brakes (in gear) the RPMS drop to700 RPMS. I think that leads to me to believe I have a leak in my break booster. Am I thinking correctly? I am going to test the vacuum right now. Be back in a min.

 

OK, the old teacher just has to respond. An idol is a thing that folks worship. Idle has several meanings, but to us mustangers it means the engine speed when you are not in gear and are not pressing on the accelerator. Now, the other word is Break or Brake. Break means you tear something apart as in breaking a branch of a tree by bending it over your knee. Brake means you are using the stopping mechanism on your stang. Therefore, they are called brakes.

 

Thanks Teach.. Anyways. Does that sound like my BRAKE booster has a leak?

 

My vacuum reading off the manifold is 11-12 IDLEing at 850 RPMS.

 

OK, vacuum is too low so either there is a vacuum leak somewhere (which might explain the drop in RPM while braking) or you need to adjust the fuel mixture on the carb. Give your vacuum lines a once over like Soaring suggested and see if there are any obvious cracks, holes, dry spots, etc. How old are the vacuum lines? When you bend them, do they feel smooth and flexible or dry and brittle?

 

run a new line from the booster and see if that solves the problem.

 

Let me go check...

 

I played around with the idlescrews on the front of the carb and was able to get my vacuum to 14 at 850 RMPS but that was as high as I got it. The only hoses i have coming off of the manifold are to the transmission and brake booster. Ipulled the hose off of the brake booster and plugged it but that didn't change the vacuum pressure. I think my booster has a leak cause the RPMS drop allot when I step on the brakes. Either way, I can't get the vacuum pressure past 14.

 

OK, since you have already played with the fuel mixture screws on the carb, we might as well set those as correct as we can. For now, leave the brake booster vacuum line disconnected and plugged since that is where we expect the vacuum leak is.

With the car off, screw the fuel mixture screws all the way in just until they bottom out (count the number of turns on each screw so you can put them back to where they are now if necessary). Be GENTLE when you do this, it's important that once you feel them stop you don't go any further. Then, screw them out two full turns. This is a good starting point for adjustments.

Start the car. Check the idle and use the idle adjustment screw on the back of the carb to get back to 850 RPMs if necessary. At this point, you should be running a bit rich. Connect your vacuum gauge and screw one of the fuel adjustment screws in a quarter or half turn at a time until the vacuum pressure starts to drop, then back the screw out about a half of a turn. Adjust your idle speed again if necessary then move to the other adjustment screw and do the same thing. This is called "lean best idle".

Post back with your vacuum reading. Don't forget to reconnect your brake vacuum line before you drive it.

 

Another thing you can do to check the brake vacuum leak theory is to press the brakes with the car running and the brake vacuum line disconnected. If the RPMs still drop, the vacuum could be fine and it could be that you have a problem with the charging system instead. Your brake lights are pulling too many volts away from the spark plugs for them to spark properly.