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]

two suggestions by other members re injector seals.
sensible suggestion.
i did mine after the sleep along with new injectors.

put them on your list to get some if you haven't done them.

another thing to get hold of is a throttle body to plenum gasket.
914 rubber has them.
worthwhile replacing that regardless. they do go hard with age.
pretty cheap little part so its not a heavy investment.

and another suggestion the plenum itself can corrode and have pinholes in it is very true.
they will likely be underneath and very had to see without getting it off.
bit of a job. notice there is a bit of surface corrosion on the intake runners.
so its a possibility.
smoke test should find them however if they are there.

[tshih914]

two suggestions by other members re injector seals.
sensible suggestion.
i did mine after the sleep along with new injectors.

put them on your list to get some if you haven't done them.

another thing to get hold of is a throttle body to plenum gasket.
914 rubber has them.
worthwhile replacing that regardless. they do go hard with age.
pretty cheap little part so its not a heavy investment.

and another suggestion the plenum itself can corrode and have pinholes in it is very true.
they will likely be underneath and very had to see without getting it off.
bit of a job. notice there is a bit of surface corrosion on the intake runners.
so its a possibility.
smoke test should find them however if they are there.

Considering all recent suggestions my plan going forward is
1) replace all hoses with new (Someone posted that Belmetric sells all hoses but when I looked at their website the search under vacuum hoses gave no results) I also need to know if someone sells a complete kit that allows complete replacement of all vacuum hoses for the 1.8L L-jet (at least list the correct id and length of each hose needed.)
2) replace FI boot (already ordered from AutoAtlanta)
3)replace throttle body to plenum gasket from 914 rubber
4)fuel injectors appear to be fine as the engine was running fine and idled at 3000 rpm so may replace the injector seals which are old.
5) measure the Fuel pressure and adjust the running pressure on FP regulator 35psi and 28 psi
6) systematically go and check/test each component as per factory manual

[wonkipop]

two suggestions by other members re injector seals.
sensible suggestion.
i did mine after the sleep along with new injectors.

put them on your list to get some if you haven't done them.

another thing to get hold of is a throttle body to plenum gasket.
914 rubber has them.
worthwhile replacing that regardless. they do go hard with age.
pretty cheap little part so its not a heavy investment.

and another suggestion the plenum itself can corrode and have pinholes in it is very true.
they will likely be underneath and very had to see without getting it off.
bit of a job. notice there is a bit of surface corrosion on the intake runners.
so its a possibility.
smoke test should find them however if they are there.

Considering all recent suggestions my plan going forward is
1) replace all hoses with new (Someone posted that Belmetric sells all hoses but when I looked at their website the search under vacuum hoses gave no results) I also need to know if someone sells a complete kit that allows complete replacement of all vacuum hoses for the 1.8L L-jet (at least list the correct id and length of each hose needed.)
2) replace FI boot (already ordered from AutoAtlanta)
3)replace throttle body to plenum gasket from 914 rubber
4)fuel injectors appear to be fine as the engine was running fine and idled at 3000 rpm so may replace the injector seals which are old.
5) measure the Fuel pressure and adjust the running pressure on FP regulator 35psi and 28 psi
6) systematically go and check/test each component as per factory manual

check auto atlanta if you want a convenient vac hose kit.
i believe you specify your model when ticking the box and get all the right hoses right length. (IMG:style_emoticons/default/beerchug.gif)

the fuel pressure regulator on the 1.8 is non adjustable unlike the earlier D jet ones.
if its not working right its a new regulator. but don't necessarily blame the regulator just yet. check the values. it might also be that the fuel pump is not delivering sufficient pressure. i rebuilt my original fuel pump completely from top to bottom (its not supposed to be serviceable apparently but the germans forgot australians love to take things apart and make them work when its not supposed to be possible). at the end of that i tested the fuel pump independantly of the car to make sure it was making pressure and also tested flow. i was making 38 ibs out of the rebuilt pump and got the spec flow rate (delivery volume over a timed period). so insufficient fuel pressure can be down to a weak worn out old pump. basically the regulator bleeds off some of that pressure the pump makes to take it down to 28 lbs at idle. but there is no adjustment nut on the correct 1.8 fp regulator. (IMG:style_emoticons/default/beerchug.gif)