76 911S runs like crap

[drola]

i bought the car a couple months ago and finally just now got the brakes road ready. car sat for a couple years before i bought it. the engine starts up without problem and idles pretty smooth. although i have a/c idle issues that's another story.
with no load on the motor it revs up to about 3500 rpm's and then starts to bog and will not go above 4500. while driving it bogs almost at any throttle input. it will get up to speed but slowly. also i am driving it around the block so i can't really even get it out of 2nd so testing is limited.
i have replaced the cap, rotor and plugs. points were changed by p.o. and barely have any miles. msd 6a ignition. stock cis.
before i go insane trying anything and everything, i figured i'd ask the experts what would be a good starting point. my gut tells me it's injection. maybe dirty injectors. will they gum up after a couple years of sitting? my next guess would be ignition. i should replace the points with one of those ignitor units. i've tested the msd unit as per their instructions and get good arc. air/fuel mixture?
any input is appreciated.

[Howard M]

Look for sources of vacuum leaks. Do a search for probable locations. Does the airbox have a pop-off valve? Check for air-tight cement joint.

[Mia911]

I say check your points...if your idle is fine and your not getting a yoyo idle...leaks might not be an issue here...check your gaping first ....wait......you say the car bogs or sputters....could be fuel also...might need to pull out the guages to test fuel pressure....

[James Brown]

and check that the advance system is working in the distributor

[drola]

how do i check the advance system?
i sprayed choke cleaner to look for vacuum leaks and found none. however the top of the two vacuum nipples on the throttle body did not have a hose on it. i capped it. where should this go?
fuel might be an issue. i should change out the filter. it sat for a couple years after all.

[RSTarga]

change fuel filter and clean out the mesh filter in your fuel tank.

[James Brown]

is there a vacuum line going to the distributor? is there vacuum in the line with the engine running? if you remove the vacuum line does the engine rpm change?
remove the distributor cap and twist the rotor and see if it's free. Check the timing advance as stated in the repair manual. If no mechanical advance is noted, then the distribuor needs to be cleaned and lubed. If everything is ok, that part can be eliminated from the problem. then move on to the CIS/fuel system.

[drola]

Originally Posted by James Brown

is there a vacuum line going to the distributor? is there vacuum in the line with the engine running? if you remove the vacuum line does the engine rpm change?
remove the distributor cap and twist the rotor and see if it's free. Check the timing advance as stated in the repair manual. If no mechanical advance is noted, then the distribuor needs to be cleaned and lubed. If everything is ok, that part can be eliminated from the problem. then move on to the CIS/fuel system.

i will check this tomorrow. i have the repair manual for my old 84 carrera but not for the 76. would the timing advance be the checked the same way?

[James Brown]

yes, but I don't have the values, same starting point just check that it is advancing as you increase rpm to 6000 w/o vacuum.

[drola]

Originally Posted by James Brown

yes, but I don't have the values, same starting point just check that it is advancing as you increase rpm to 6000 w/o vacuum.

isn't it the vacuum that causes the advance?
the rotor has a little play while on the shaft but does not spin free.

[drola]

sorry, just realized the mechanical advance part of the distributor.

[James Brown]

no it won't spin free just turns a few degrees. Q: how much vacuum is there at wide open throttle?
A: none. so the mechanical system is the only thing working when accelerating through the gears @ WOT. Vacuum advance is only used at idle for pollution control and smooth idling, more or less.
If the rotor moves clockwise (advance) then it most likley is ok, just check it with a timing light.

[drola]

doing more research (i can't thank out host enough) it seems like the symptoms point to the mechanical advance. i will check it out tomorrow. if that checks out good then i know to move on. james brown, i really do appreciate your input.

[James Brown]

No problem, we all gain from your pain!

[drola]

well, i got the dizzy out to clean the weights. one of the springs is stretched and holds no tension at all. also it seems like there should be some sort of seat for the spring on the tab where it sits. the weights did not go all the way out at first but once i pushed them out to the stops they move freely. i read gunter's dizzy maintenance thread and was posting the same there. take a look:

[Walter_Middie]

Your distributor definitely needs cleaning.

The springs are correct, but they are supposed to sit on small plastic sleeves. These get old and break. Yours are gone. I made some for my car by using very small thin plastic tubing.

Check your advance by connecting a timing light and reving up the engine. You should see the timing change with RPM.

[cgarr]

Could have a fuel pump gong bad, these engines are very sensitive to proper pressure, had same problem with our 76. Pressure should be around 72# if I remember correctly.

[drola]

Originally Posted by cgarr

Could have a fuel pump gong bad, these engines are very sensitive to proper pressure, had same problem with our 76. Pressure should be around 72# if I remember correctly.

fuel pump works. i haven't tested pressure though. i figured i'd get the timing issue settled (mechanical advance) and then go on to fuel. all the pressure in the world will not make a badly timed motor run properly. so yes, i agree with you. pressure is definitely something to look in to and that's next on the list.

[Gunter]

Just noticed some details.
If this CIS sat for a number of years without having had any cleaner run through it, some work is needed.

I would remove all injectors and soak them fully submerged in a small can of injector cleaner for couple days.
Use 2 wrenches to loosen the cap-nut on the line first. Then use the 2 wrenches to pry on the cap-nut from underneath to pop out the injector. Spray a little WD-40 onto the O-ring to make them pop out easier and remove each injector. Soak them for at least 24 hours, then blow them out.

New fuel filter is good but.................if the tank is dirty, the filter will clog up very quickly.
You can inspect the tank by carefully removing the level sender and looking inside. Careful with the flashlight, it's fuel and vapor!
Some people not only clean the tank but also blow out the lines leading to the rear.
If the tank looks clean, proceed.
On a full tank, use 2 bottles of Injector Cleaner like Techron and run some of it through the system.

[drola]

yes cleaning injectors and inspecting the tank will be my next project.
put the distributor back on and it made a huge difference. i will get my hands on a timing light and check the advance. still not running on all 6 though but i think the injectors should solve that.