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?

[wonkipop]

wow @tshih914

that was a quick test and reply.
we are making some progress.

first thing. fuel pump may be original or original type.
but its definitely not in stock position for a 74 L jet.

would appear its had the by now common modification of a move up to front of car under fuel tank to guard against vapor lock.
(the original stock position is right under the engine on right hand side tucked right up above the heater tube that goes into the longitudinal).

given the behaviour after you unplugged the afm its definitely not stock OEM wired in. i'd say its running off the ignition circuit.

i'd have to think about this a bit.
no doubt @Van B will come in again at some point.

but the behaviour with the AFM unplugged was not exactly the same as with it plugged in by the sounds of it. i would have expected it to be exactly the same if the fault or problem was that the AFM was not sending a signal and the car was just running off the fuel pump triggered by the ignition circuit and the throttle position switch at idle.

i'd probably think at this stage there was a signal getting through.

i'm going to go with the idea that the AFM signal is not a problem.

you should turn to the second test now.
pull the hoses off the decel valve and plug the hoses so it can't pull air.
try starting it. it should go. and idle should be reduced to level it was when you clamped the decel valve. but you might find the idle air screw is too closed and you might have to adjust that to get it to idle. its been getting a lot of air through that decel valve. but its not "leaking" air. it is actually metered air. it will have been pulling the AFM flap open. the AAV will have too. so this is not an unmetered air leak.

and then try gassing it after you have got it idling.
this should be a good test for @Van B 's thinking its falling over because it leans right out the minute you open the throttle.
see what happens and let us know.