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?

[Van B]

@wonkipop if the decel valve is full flow, it could still make the car stall as soon as he touches the gas because you're just introducing even more air into an already excessively lean scenario.

that said, I agree that this symptom is way to similar to what we learned about how the engine acts when the AFM is unplugged/dead and the fuel pump is DAPO wired.

[wonkipop]

@wonkipop if the decel valve is full flow, it could still make the car stall as soon as he touches the gas because you're just introducing even more air into an already excessively lean scenario.

that said, I agree that this symptom is way to similar to what we learned about how the engine acts when the AFM is unplugged/dead and the fuel pump is DAPO wired.

yes agree re the decel valve/lean scenario.

test i have suggested is another easy one to do without jiggling or mucking about with anything much.

just methodically ticking it off.

he should definitely go and adjust the decel valve following your instructions in thread you linked to. but before he takes if off and does that, just to run this test.

and tell us how the fuel pump is wired.

it won't exactly nail it down to the ECU connection.
but i'm thinking about how he reported the problem initially arising.
progressively more difficult starting.
then it dying when he gassed it.
to me this is the real problem he has?
that could point to either poor contacts in the AFM unit itself or a dodgy ECU/AFM connection. progressive degeneration of an electrical contact? he has a new AFM now, so its unlikely to be internal to that.
but the other two parts could still be the issue.

he has subsequently done more work on the fuel system.
so now it appears to start ok, but run only at idle.
so something did change.
we both know how that can happen if the fuel pump is not wired OE.
it can and will start easily. with that plug out. when it should not.
but it won't do much else.
i guess i am interested in whether his work in between has resulted in this easier start.
but thats all its resulted in. and its a bit of a smokescreen.

and perhaps most importantly in between these two states of affairs it seems it ran fine for a while!!!

lets see.

i'm also looking at that ECU which is very evident in photos to be in a less than desirable state of affairs. perhaps he has just disconnected its mounting as he undertakes this work. but its not great.

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after he reports back we could also get him to run an easy test on the decel to explore your suggestion. even before he adjusts it he could take it out of the equation by pulling the hoses out of it. and plugging the hoses. it should still start i think, even without all that air its getting from the decel - but start and idle lower.
he can then give the throttle a tweak and see what happens. ie does it die once it comes off TPS or will it respond to throttle and not die.

but i am thinking one step at a time.

do test i suggest above in previous post first.

then do the decel valve delete test second.