75 1.8L Ljet starts, goes to high idle, then dies. Will not Idle. Did a smoke test, had a cracked phenolic spacer. Replaced the spacer and it does the same thing. The spacer cracked as it did not clear the engine tin. I adjusted the tin and made sure it seated on the head.

@Geezer914
Is it dying also even if you try to rev it?
AAR (auxiliary air regulator) is open when engine cold or initial start, that will provide air to make the idle higher. And when engine getting a little warm, AAR will close (assuming AAR is functioning well) and makes the idle lower (which is supposed to drop between 800 to 900 rpm. Again, if your engine run when you rev it, probably wait till it warm up properly then try to adjust it using screw driver on the adjustment below the throttle and get an idle around 850rpm.

It is not the aux air valve. The engine starts revs to 5k and if you step on the gas, it drops to 0 rpm and dies.

Still a vacuum leak? I would guess about the size of a 13mm hose.

check gasket on oil cap

5k? or is that a typo.

That's what mine does when I pull the pcv or the decel off the plenum. It doesn't die of course, it's a djet.

i think the pcv valve hose on a 1.7 goes into the intake plenum after the throttle body.
and it is a big hose.

on a 1.8 the pcv valve hose connects before the throttle body. will still upset things i suppose. a leaky oil filler cap on a 18 as suggested will also upset idle. usually thats an unstable idle or slightly high idle?

curious about 5k mentioned, would call that a racing engine rather than a high idle?
if 5k is right, that almost sounds like a throttle stuck open?

a leaky decal valve or connection hose on a 1.8 does feed directly into the intake plenum. its a small hose not a 13mm hose.

my 1.8 will do the almost die thing when its cold if i give the throttle a poke.
and i'm pretty sure thats because i have a disconnected decal valve. but it kind of dies for an instant and comes back to life. goes away when properly warm.

i'd be checking every hose to make sure they were all on.

chased down a vacuum leak on mine last summer. but it was a hunting idle problem.
usually what happens with a 1.8 with a small vacuum leak. turned out to be a throttle body gasket that had gone hard - showed up only when the engine was properly warm.

this sounds quite a bit different.

Looks like you have both a decel valve hose and an aux air hose that could leak like that.

Typically our Ljets won't run at all with a large enough vacuum leak. I think something else is going on here. If you start the car, and the rpm's run up to infinity, points me in the direction of the air flow meter. After the engine runaway, it turns itself off, which points me to the dual relay. It would be interesting to see if you were to back probe pin 88a or 88b on the dual relay to see if your dropping 12 volts.

Does the 1.8 have a throttle body butterfly?

Fuel lines crossed?

Yep

Is it open or closed? I suggest lines because he was mucking around in the engine bay before this happened (intake gaskets). Easy thing to knock off the plenum, he may have fixed one leak only to make another.

Cured all the vacuum leaks! Car starts and no longer climbs to a high rpm. I can hold the rpm to 1500 rpm, but if I let off the gas it stalls. So I need to adjust the timing and play with the throttle body.

Engine specs:

1.8L block built to 2056.
Raby 9550 cam
Vanagon 50mm throttle body modified to fit the 1.8 throttle valve switch.
Mallory Unilite distributor with silver springs.
Ljet fuel injection
Air Flow Meter was refurbished by Fuel injection Corp.
ECU was tested and in working order.

That sounds like an awesome engine.