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]

i just watched your video @Van B .
your decel is rigged right or at least same as diagrams and how it is normally done.

i'm looking at his and it looks the same.
from what i can see of it.
but it would be nice to see a close in photo just to be sure.

[tshih914]

I have every vacuum hose hooked up the same as the diagram that wonkipop posted. My photo show the 2 plugged ports to the side of decel valve and the t leading to the boot (I will be ordering a new one from AutoAtlanta as the one currently in the car is an old used one from eBay that I got when the AFM explosion triggered the search for cause of stalling after starting). I have also removed the hose connecting the two ports
as instructed for this test. The idle adjustment screw at the base of the throttle valve was adjusted 2 turns from fully closed. I did mention that while the engine was idling at 2500-3000rpm I did try to cover the air filter box's snorkel with my hand and the engine did not stall indicating that there must be a vacuum leak. When I get the new boot installed I will hunt for the source of air leak with the Smoke in a can used to test fire alarm smoke detectors.
I just reattached the hose and started the engine after many cranks to get it idling at 2800 rpm before repeating test3 and 5 (wonkipop's earlier posts). When hose to side port of decel valve was pinched closed RPM dropped by 400-500 rpm. When AAV hose was pinched rpm dropped by 800-1000rpm. The smoke in a can wasn't useful in finding the source of air leaking pass the AFM pathway.

[wonkipop]

I have every vacuum hose hooked up the same as the diagram that wonkipop posted. My photo show the 2 plugged ports to the side of decel valve and the t leading to the boot (I will be ordering a new one from AutoAtlanta as the one currently in the car is an old used one from eBay that I got when the AFM explosion triggered the search for cause of stalling after starting). I have also removed the hose connecting the two ports
as instructed for this test. The idle adjustment screw at the base of the throttle valve was adjusted 2 turns from fully closed. I did mention that while the engine was idling at 2500-3000rpm I did try to cover the air filter box's snorkel with my hand and the engine did not stall indicating that there must be a vacuum leak. When I get the new boot installed I will hunt for the source of air leak with the Smoke in a can used to test fire alarm smoke detectors.
I just reattached the hose and started the engine after many cranks to get it idling at 2800 rpm before repeating test3 and 5 (wonkipop's earlier posts). When hose to side port of decel valve was pinched closed RPM dropped by 400-500 rpm. When AAV hose was pinched rpm dropped by 800-1000rpm. The smoke in a can wasn't useful in finding the source of air leaking pass the AFM pathway.

ok thats interesting @tshih914 about the snorkel.
it wasn't clear to me whether you just had your hand near the snorkel feeling for air flow or had you actually blocked it off.

yes the engine should die if you fully block the snorkel.

positives so far.
you definitely have a farked up decel.
it might come back to life with an adjustment.
if it doesn't you might still be able to source one but they are hard to get hold of.
or you can do a decel delete.

for clarification when you first did the tests i suggested, you reported the opposite results. decel dropped it by about a 1000 rpm from 3000 to 2000. AAV drop was less.
you did not give a specific number but described it as less than the 1000 drop due to the decel.
EDIT correction. went back and read the first test results. decel was 3000 to 1000. drop was 2000 revs.
AAV drop was less.

this repeat of the test seems to be the other way around/different?

guessing difference in part is due to you having the t/b idle screw out on this second test?

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i think both of these components need to come off and be tested.

onward looking for more.

do the second smoke test.

i would also suggest a proper f p test.
i think i can see you still have your fp gauge plumbed in.
and its in the circuit before the regulator? which is good.
so you can do this test now fairly easily.
when its running you either pull and plug the vac hose into the back of the regulator or just pinch it tightly shut. the fuel pressure should be 35+/-. with the hose back in or the clamp taken off it should fall to 28. i know you have tested it and got 28. but that would have been the vac hose on value. be good info to know if its building the full pressure thats needed to acceleration/load phase.

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