1974 1.8L engine fast idle then stalls, Fuel injection issues Options

[tshih914]

My 1.8L 914-4 with stock Bosch L?-Jetronic FI after being stored several years started to develop a hard to start problem. When finally started would stall when I give the gas pedal any input to raise the revs. I suspect there was some kind of intake air leak and while fiddling around had a backfire which blew the AF meter which I had Pelicanparts repaired. After replacing the fuel lines with the stainless ones from Tangerine Racing and flushing out the fuel system with Techron the engine started to run normally for a short time. Now the engine can be started and fast idles at 3000 rpm but again any input to rev up the engine results in stalling. The idle adjustment screw at the base of the throttle housing is fully closed. Any suggestions on how to fix?

[rhodyguy]

Would a vacuum leak down stream of AFM result in a low idle not a high one?

[wonkipop]

Would a vacuum leak down stream of AFM result in a low idle not a high one?

thats been my experience.
air leaks usually mean it won't idle at all or it will have an unsteady idle and hunts around. air leaks won't pull the AFM flap, so usually they lean out.

@tshih914

these are handy if you don't have them.
factory workshop manuals.

http://p914-6info.net/Manuals.htm

you may as well download them all (except 914/6 specific).
fuel injection = group 2.
has all the trouble shooting checks for each L jet component.
its a bit tricky to read as its mixed in the with D Jet stuff.

back to high idle, i suspect this is the decel valve.
its come up before with two other members.
fits the pattern. idle stuck at 3000 rpm.
i'd have to dig up the thread.
but @Van B can probably find it easily, he was the original poster for one of them.
or he can lay out the precise process for testing the decel valve to see if its good,
and also to adjust it. the decel valve is adjustable.
its diaphragm has probably stuck.
the air route through the decel valve will pull the AFM flap and let the ECU know its wanting the fuel to match the air. even though the throttle position switch is letting the ECU know the throttle is closed and at idle position. in other words it is perpetually stuck at halfway down from open throttle to closed throttle.


accurate vacuum hose layouts are here on page 3 of this thread.

http://www.914world.com/bbs2/index.php?sho...57407&st=40

for 74 models.
you can check your vacuum hose set up just to be sure.
but i don't think its going to be an air leak that is causing the high idle.