Vacuum lines

Ok, so I think my vacuum lines are all messed up. You see, my 74 mav(250 I6) shakes pretty bad at idle and after about 5 minutes stutters and dies. I couldnt find any vacuum leaks, so I have to assume my lines are all in the wrong spots.

Now I didnt move the lines or anything, but there are only like 3 lines hooked up, which I guess you only need two, but maybe the two I need are in the wrong spot or non existent. Here is what i have;

I have one line that goes from the ERG valve on the carb to a metal line that leads into the lower engine, another line coming from the top port of the vac advance on the distributor(side port is capped) to the right port on the manifold. Then from the left port on the manifold to the firewall, them from firewall down to transmission, and from there to a curly metal tube to center port of manifold, thats it.

So I dont know, the last owner I guess did this. I just want to fix it. Any help or suggestions?

Thanks

 

Does your car have Califonia emissions???Is every thing else on the car up to snuff??(plugs,wires,cap rotor etc...)Run a line from the intake to the steel tube that goes down the firewall to the trans.Its for the trans vacuum modulator(check and see if there is trans fluid in that one also/if so you need a vacuum modulator for one thing).Gotta have that one.Check the other end of it see if that hose is bad.Dont replace that steel line with hose.It needs to be steel. Plug the other ones and see how the car runs.As for the egr valve(could be the source of your drivability prob) if its stuck open.Depending on emissions regs in your area you may need to leave that one in tact.The vacuum advance on the dist should not be connected to constant vacuum.(the intake manifold)It should be attached to a ported vacuum source.For now you can leav it disconnected and plugged.Hope this helps you out some.

 

Well, It was bought in California. I will the DSO to see what district its from I guess. Where I live I am emissions free, so that is no concern.

The wires, plugs, and cap are all new. I guess I will check the metal lines, however im not sure what you mean by ported vacuum source.

thanks for the help.

 

Ported vacuum is vacuum that is sourced from above the throttle blades on the carb,That way vacuum comes on only when the throttle blades are opened beyond a certain point.Your car may have several devices called PVS.Usually they are mounted in areas where they will get heat from the engine coolant.EG:Thermostat housing,water jacket on block/head.They have a hex at their base and a tower with one/two or several nipples for vacuum lines to attach to.If the emissions tag is still on the shock tower,it should say on it if its Cali emissions.

 

Thank you mavman for the help. I was not able to check the modulator on the trans, but I did hook the lines from the dist to a pvs to the carb and I saw an immediate improvement.

However after about 5 minutes it would stutter and die, and from there on out after starting it, unless I was giving it gas it would just die. I opened the choke on the carb to pretty much full open and it runs fine. So I dont know? Any more suggestions please?

PS, I checked the emissions tag and yes, it is California emissions.

Thanks again.

 

With the choke open it now runs fine? no stalling,hesitation?Choke staying fully closed would cause the car to stall once warm(over rich condition)I cant help but think you may have a fuel delivery problem.Pump volume too low,float stuck partially shut keeping carb from filling with fuel in a timely manner.Plugged fuel filter.Is your gas tank original and is it rusty?? rust in the tank will cause the sock on the end of the pick up to plug up.Did you remove the vac hose from the EGR valve and plug it?? A stuck open egr valve will cause the car to run bad/stall once the idle drops to normal after warm up.

 

Yes, runs fine, no stuttering, just like a normal I6.

Well, I have a brand new fuel receiving unit, new filters, I did plug the EGR. However I did recently install a new carb, when I first installed it the float was suck closed. So I had to shake it a bit to get the float open. I will see if I cant tap it a few times to see if that shakes the float loose if it is partially closed.

Thank you for your suggestions mavman.

 

Shaking the carb isnt good(upsets float/needle)If car runs good now,you have a choke problem.

 

Thank you for your help Mavman, I think I figured it out, had to do with the idle mixture and such, runs fine now. Thank you so much for your help, wouldnt have been able to do it with out you.

Thanks again.

 

Glad I could help.Pete.