joekuntze

i have almost completed my intake refresh i have 2 issues i could use some help with
car is 88 s4 manual
1) i have redone fuel injection vacuum but there is a black vacuum line coming out of the firewall that is cut. i didnt cut it and have no idea where it goes is it possible that it is from the factory and is for those cars w automatic trans?
2), i have a black 3 wire female plug about the size of the knock sensor plug originating at wire harness back of engine form same cable as throttle body sensor i dont have any idea where it goes

any help appreciated thanks in advance
joe

Jim M.

Pictures would be helpful.

FredR

Photographs not withstanding, suggest you list the vacuum connections you do have so we might have a clue as to what if anything is missing. A black line crossing the firewall sounds like it should be the vac feed to the HVAC system from the vac reservoir [it is the only one that crosses the firewall] but....?

StratfordShark

I wonder if you unplugged the CPS (crank sensor) which plugs in on the bracket carrying throttle cable pulley? That's the only 3 wire I can think of in that area.

Not sure what you mean by "fuel injection vacuum", so please post a photo if you can showing where it is and where the ends you can see are.

It will all go back together perfectly in the end!

FredR

There are two three pin plugs in that area, one is for the CPS and the other is for the throttle position switch. The car will not run without the CPS connected and worse, some folks have managed to get the two plugs connected the wrong way round and then wonder why the car will not start.

Meatful

My S3 has vacuum lines for the EZ box in the passenger footwell as well as HVAC vacuum roughly in the area you describe.

Does the S4 have the "timing mark sensor" (91160610800) running to the flywheel area like an S3? If so, the connection point location for the other end on mine stumped me until I pulled pics showing it is unterminated and secured to the aft intake runner as a service port.

joekuntze

this is the 3 wire connector i suspect that the suggestion that nit is the crank position sensor is correct i will pull the intake (AGAIN) to verify and re connect

this is the open line the blue masking tape is at the open end and as you can see it is fixed in place by the white nylon connector before it disappears into the firewall behind the black nose in the upper left of the photo


photos as requested

i have one vacuum line under intake connected to charcoal cannister the other to the fuel dampers and pressure regulator the one to the air diverter is plugged and i have one from the flappy to the port at front the 4 wqy drivers fender well connected to brake master, heater valve orange line for hvac and lower port solenoid front of car

thanks again guys

joe

FredR

There are in effect two vacuum systems on the car- the "active" system and the "passive" system.

The active system functions depending on the amount of vacuum the engine is pulling at that moment in time and this modulates as the throttle is open or closed. The vacuum supply is taken from under the inlet manifold downstream of the throttle butterfly on the top of the casting. The line runs to a multi way rubber manifold located behind the MAF and this supplies vacuum to the FPR, the two fuel dampers, the auto gearbox modulator. There is also another single vac line taken from a connection upstream of the throttle butterfly that goes to the tank vent system.

The passive vacuum system is located in the area around your photo. There are 4 connections from the 4 way sub manifold- the vac supply from the check valve, the fill line to the vacuum reservoir, the line to the flappy valve and the line to the HVAC that would appear to be the black line you are talking about. If this line is not connected the HVAC system will not work as designed given it requires a constant vacuum supply to drive the actuators as and when the HVAC control logic demands.

Koenig-Specials 928

Joe I don't know how different your 87 is to my 89 but this is what my 89 Vacuum Routing effectively looks like.
Hope this helps. Your missing vacuum line is circled in red (John Pirtle's pic).
As FredR indicated it is feed for the HVAC system

joekuntze

WHERE DOES THE LINE TO HEATER VALVE ORIGINATE?

FredR

Under the centre consul behind the radio

joekuntze

ok so my 4 way intake looks like this BUT the vacuum diagram i have shows there is a line from one of the ports at the front of the engine near the fuel damper on the drive side plugging into the port where the line form the firewall is supposed to go is there another connector down in the driver fender?

StratfordShark

There are 4 connectors to the 4-way:

Vac feed from check valve
Vac feed to HVAC manifold
vac feed to reservoir
vac feed to flappy solenoid

the last one is the only vac line running to front of engine.

joekuntze

ok but i am really confused now
on the bottom of the intake there are 4 vacuum nipples

one to charcoal cannister
one to solenoid front of engine
one to air pump solenoid (plugged on my car
the last one is to the black plastic device i thought was the flappy actuator. where does that go ?
thanks

StratfordShark

The vacuum line operating flappy actuator should run to front of engine, and plug into solenoid mounted to bracket front left. The solenoid switched a vac feed to that line which comes from the 4-way spider at heart of 'secondary' vacuum system.

You say you have one line going to solenoid front of engine. Can you trace it back to the flappy valve? You can confirm by detaching from solenoid and applying vacuum and looking for movement of shaft at top of intake under rubber cap. If necessary just suck on it!