i have a 1979 ZX .. starting up in the morning (no problem!).....starting when hot ( PROBLEM! )...it sounds like its choking out , then runs rough....gas mileage sucks!!...help me out?

 

Welcome to ZDriver!

I suggest starting w/ the basics...

Read the spark plug tips... color? wet? dry? build up? Do any look different than the others?



Do a basic check over and tune up. Replacing worn out plugs, wires, cap/rotor, air filter, checking fuel pressure, running FI cleaner, will do wonders for a neglected car. Check all sensors and connections. They are prone to corrosion.

 

check the timing it may be too retarded.

 

Also check your CSV (cold start valve) it may be leaking. When the car is warm its no longer needed so if its leaking its burning extra un-needed fuel.

 

i have the same exact problem on my 79, it runs great if i keep it on, then if I warm it up and shut it down, go away for about 30 mins then go to start it again it will idle roughly at like 400 or 500 rpm, and if you give it some gas it almost feels like it miss fires, but doesn't stall, I have tried replacing the pcv valve, the cap and rotor, ignition and none of it worked, by the way its not the O2 sensor, mainly because 79's didnt have them lol, as I came to find out. so if you find the solution please tell me! lol

 

Have you checked the gas cap, it might not be getting a good seal. Not sure if it will work or not just tossing it out there.