I have a 1985 gs manual trans. ,154K miles.. it was running great.. a drive the car every other weekend, last saturday a took the ca for a drive for about 40 minutes and average speed of 75 miles/h.. after i exit the freeway the car estar idling very rough, rpm when up to 1500 .. by the time got home the car was almost cutting off....i tri it after the engine was cool.. and is the same situacion.. the rpm goes up nice and easey and no miss firing in the high rpm range.. but its almost cutting of because of the rough idling!...help please!

 

vac leak, retarded timing, perhaps shutter valve.

 

i would start out by checking for vacuum leaks for sure..that'll give you atleast a head start, i'm sure the timing should be fine since you did say it WAS running great until that long drive...

 

Be sure to check this hose.

https://www.rx7club.com/1st-generation-specific-1979-1985-18/hose-question-750125/

 

thanks for the pictures (74rx4) and i did not found any leaks in the vac.. hoses that hose is in very good condition. but i pulled out and it cut off the engine right away. and thanks everybody for the help... the car is running great again. a think it was the air vent solenoid.. like a year ago i rebuild the carb when i pulled out it was kind of stuck.. and a think is no to free in the housing( the hole) after i try all the sugestions took the air filter housing and blow some air from the top into the hole that hold the air vent solenoid.. some gas came out to the carb....put everything back star the engine and great.. is back to live..I love it.. againg thanks a lot guys for the help....