Question - recently replaced my carbs with rebuilt ones on a '71 240Z.  Managed to get the car started but it is doing the strangest thing.......I have to keep the choke open and it will drop down to 500 rpm's and then go up to almost 3,000 rpm's without me touching anything??  It's crazy!  The gas pedal is non responsive to??  I try to keep the car going by stepping on gas but it does NOTHING.  I think I have another issue that is not carb related.  Any ideas?

Hi Jeff.....Glad to know you’re getting your hands dirty. Sounds like your linkage isn’t hooked up correctly. Who rebuilt the carbs? Are the jets turned down 2 1/2 turns on each carb. I hope Ztherapy built the carbs. Happy New Year to you and Sue.

Diseazd - the carbs came from Jim F. so I know they are perfect.  Linkage is hooked up correctly.  I think it's a separate issue???

I say linkage too.  Those flats by each carb has a certain way you stack them.  I put mine on wrong and shot up to about 3 grand too.

I looked at that SU diagram from the fsm and all the real images I could and figured it out.

Good luck, I know it scared me.

Had a similar issue where the car would idle very high then  low and oscillate back and forth with high and low RPM, gas pedal non-responsive.  Problem was a large open hole in the back of the balance tube where one of the fittings (PCV?) was missing.  Once I plugged it, she ran like a champ.

Thanks guys....I think the linkage is OK but will double check.