Shaking, back and forth motion at 1st and 2nd gear

[Patcon]

If the idle goes up with the booster unhooked I would suspect it is leaking. I agree drive it with the booster unhooked. BE CAREFULL you will still have brakes but no power assist.

[jalexquijano]

The bumpy road thing makes me believe it's a motor mount messing with your throttle linkage. Go over your throttle linkage very well, insure everything is lubed, and free of any stiction. This started happening after your ztherapy install as well?

If you get a change in idle speed you may probably have a small leak in the booster. For future testing and troubleshooting keep it blocked off. Did you drive it at all with the booster blocked?

Yes! this started happening after my mechanic istalled both of the su carburetors Ztherapy remanufactured for me completely. i only see two motor mounts and dont notice them broken!

[HuD 91gt]

Take a very close look at the linkage, and look very closely at diagrams and other photos of linkages online.  It's possible he got mixed up when putting the carbs back on.  It's a long shot, but you never know.  I had mine installed wrong at first.

[jalexquijano]

Take a very close look at the linkage, and look very closely at diagrams and other photos of linkages online.  It's possible he got mixed up when putting the carbs back on.  It's a long shot, but you never know.  I had mine installed wrong at first.

I will try and disconnect the actual fuel pump and install the one in the picture back! My dad think it could be fuel starving at low rpms! I dont think it would hurt to put the 5 to 9 psi Airtex 8012S electric fuel pump back and measure the real psi!

[Stanley]

Keep a fire extinguisher handy if you do that. FSM says max fuel pressure for SU's about 4.3 psi.  9 psi is more than double. Too much fuel pressure can overpower the needle valves and cause the float bowls to overflow.

[oranngetang]

If not a fire extinguisher, a GoPro just so we can see what happens.

 

Better yet, use it to record the problem you're having so everyone isn't guessing at a written explanation. We all use different words to describe the same thing. It'll clear up a lot of confusion.

[jalexquijano]

Just swapped it and even after turning to 3.5 turns each carb, the back and forth shaking movement at 1st and 2nd gear is still there. All the 3 mounts (engine and transmission) are perfect and not cracked. The problem is sure another thing!! I did not had this problem with the FAR 311 RACE CAM!! Could the distributor have an inner short or damage?

[HuD 91gt]

I'm sticking with linkage issues. Take pictures of it and someone will at least be able to take that out of the equation.

Others have requested videos. Your not gojng to solve the problem by just guessing and changing out all the parts. You need to diagnose it and eliminate issues. It will get very expensive the way you are doing thjngs.

[jalexquijano]

The car Works perfectly over 3000 RPM and there is no hesitation at high idle so i do not think it is a vacuum advance or distributor inner problem issue.

[Patcon]

Did you ever solve this problem?

[jalexquijano]

Thanks for the follow up Friends. I decided to purchased all the vacuum related braided hoses and took the car to a Porsche Carburetor type car mechanic here in Panama. He took 2 weeks to tune the car and replaced all the braided hoses. The hesitation and stumbling is gone. Did notice that while the car is parked for more than 5 minutes the idle lowers from 950 to 800 and rises back. I guess this is normal in this type of cars. It does not shut down.

 

Anyway i asked him if it was an electrical problem or if the dizzy needed replacement and he said no. He tuned both carbs by ear and now i dont know how many turns he gave to the idle mixture knobs? to determine how many turns he gave should i take the carb domes and pistons out and start turning counternclockwise until it closes fully, write it down and then clockwise where he left them?

[Stanley]

A Porsche mechanic? Just drive !