MPS testing and where get rebuilt, Slight loss of vacuum after 5 min ? bad MPS Options

[jsf322]

I just checked my MPS because my car is running rich, burns a lot of fuel, and idles very poorly especially when warm. The CHT was bad and I replaced that. IT improved the stalling I had before replacing it, but the car is still rich and idles very unpredictably. I put 15mm Hg on the MPS and it lost about 1/2 mm in the first minute and 4-5mm within 5 minutes. Would that be considered a bad MPS. If so does anyone have experinece with rebuilt units from AA or Preformance Products. AA is about $40 cheaper. Thanks for any input.

[jsf322]

okay here is some more information. The valves were adjusted about 500 miles ago as well as the timing checked and the dwell set. I tested the temp sensor at the throttle body and it gave the correct numbers. The CHT I replaced because the wire going into it was having issues and when it moved slightly the car would stall. Now it does not stall. When I first start the car it dies and will immediately restart and stay running. Sometimes if I try to move it right away it will pop back a little if I do not give it a lot of gas. after a minute or two of running there is no problem with that. There are times when it will idle rock steady, but if I push the pedal down at all when it is idling well it will immediately start to go up and down on idel from almost 0 to about 1000 rpm. When I pull up to a stop the car drops idle for a moment to almost a stall and catches and is okay but idle wanders. I can smell it running rich and it is only getting about 21-23 mpg. I will check the ECU and MPS to see if the numbers match but from what I know of the car they are original to the car. Th engine only has 44K original miles and not much was done to it over the years. I have replaced all of the vacuum lines and fuel lines except the ones in the tunnel because they were amazingly good. The fuel pressure is about 30-31 lb. The car has plenty of power when driving and no hesitation at any point in the full RPM range after idle.

[Bleyseng]

okay here is some more information. The valves were adjusted about 500 miles ago as well as the timing checked and the dwell set. I tested the temp sensor at the throttle body and it gave the correct numbers. The CHT I replaced because the wire going into it was having issues and when it moved slightly the car would stall. Now it does not stall. When I first start the car it dies and will immediately restart and stay running. Sometimes if I try to move it right away it will pop back a little if I do not give it a lot of gas. after a minute or two of running there is no problem with that. There are times when it will idle rock steady, but if I push the pedal down at all when it is idling well it will immediately start to go up and down on idel from almost 0 to about 1000 rpm. When I pull up to a stop the car drops idle for a moment to almost a stall and catches and is okay but idle wanders. I can smell it running rich and it is only getting about 21-23 mpg. I will check the ECU and MPS to see if the numbers match but from what I know of the car they are original to the car. Th engine only has 44K original miles and not much was done to it over the years. I have replaced all of the vacuum lines and fuel lines except the ones in the tunnel because they were amazingly good. The fuel pressure is about 30-31 lb. The car has plenty of power when driving and no hesitation at any point in the full RPM range after idle.

1. change out the points to a Crane optical points replacement. Electronic ignition is a big help.
2. Set the idle mix when the engine is hot, after 15 mins of driving, AAR valve is closed.
Use a CO meter if you can get one, go to a shop etc.....or
pull over after the car is hot and reset the idle ECU screw to where the engine idles good and reset the idle speed to 950. Do it a couple of times. The idle knob on the ECU should be close to the factory notch.

It sounds like the idle mix is rich a bit. Make damn sure the vacuum hoses are setup correctly.