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]

@tshih914

we are getting somewhere.
this time it did not stall, it almost stalled, but did not stall.
it did try to do the transition to open throttle.
not very well. but it showed hopeful signs! (IMG:style_emoticons/default/smile.gif)

the first time you sealed off the decel hoses it dropped to 1000, much lower than the 2000-2500 with this test. that was because in the first test the idle screw was closed completely shut. the engine was getting a significant portion of its air from the decel valve. to the tune of about 2000 rpms worth. now some of that air that was being supplied by the decel for the elevated revs is being supplied by the idle air passage being opened up.

the auxiliary air valve is probably supplying some rpms worth going by the tests.
when you pinched that one shut in the earlier isolation test you said the rpm dropped but you did not say by how much. if it was in proper working order it would have been in the order of 400-500 rpm worth stone cold. getting less as it warmed up and closed.

from here you really have to go through each component one at a time and test them.
you will need that factory manual i gave link to in page 1 of this topic.
you only need section 1 (engine) and section 2 (EFI).

it will be interesting to hear from other members.
there are some very knowledgable L jet guys on the site.
@Van B will likely have something to say now that could be useful.

i'm going to think about it a bit more.


EDIT
thanks for the VIN label. its built the week before mine.
got the same brown interior.
when we get to the end of this and hopefully get the old girl running i'll ask a favour of you for some archival info, but not now, lets get her going. (IMG:style_emoticons/default/beerchug.gif)