When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
Hooking up my lines after an intake gasket swap and I think I broke/never had hooked up in the first place these two vacuum lines. I can't figure out what they are based on the 1987 E4ME vacuum line diagram as everything else appears to be accounted for. I've got one coming from under the passenger exhaust manifold and one from the wiring harness in the back passenger side behind the AC dryer. The one from the back MAY be the EFE line per the diagram below but I can't figure out what the one by the manifold is.
This one is coming from undiscernible area below the exhaust manifold on the passenger side This is coming from the same wiring harness as the EGR solenoid. This could possibly be the EFE line? I'm not sure.
The heater control, that little flying saucer looking guy hooked up to the coolant lines, is plugged in. So it’s not that, unless you’re describing something else?
If you have a heater control valve under the hood (some cars do, some do not), then there are 2 vac lines between the cabin and the engine compartment. One is "supply", the other is the line to the HCV. They come through the firewall with the HVAC wiring harness, which since different cars have different HVAC systems, is its own little discrete harness separate from all others. It passes through the firewall in a grommet near the heater hose fittings.
All the motors under the dash that control the air routing doors, are just vacuum diaphragms. There's a little vacuum valve on the control head that sends vacuum to them all to make them do their thing. The valve has to get vacuum from somewhere to do that. Furthermore, this vac supply has to be isolated from the intake manifold itself, by a check valve and reservoir; otherwise every time the vacuum goes away, such as when giving the car some throttle, all the little doors will reset. The cruise control gets its vacuum from the same check valve/reservoir subsystem, for the same reason.
Since the HVAC system (and reservoir and all that) AREN'T part of "the engine", but rather of "the car", none of it is on the emissions hose routing diagram. Just as the cruise isn't. But that's what that line looks like to me.
If you have a heater control valve under the hood (some cars do, some do not), then there are 2 vac lines between the cabin and the engine compartment. One is "supply", the other is the line to the HCV. They come through the firewall with the HVAC wiring harness, which since different cars have different HVAC systems, is its own little discrete harness separate from all others. It passes through the firewall in a grommet near the heater hose fittings.
All the motors under the dash that control the air routing doors, are just vacuum diaphragms. There's a little vacuum valve on the control head that sends vacuum to them all to make them do their thing. The valve has to get vacuum from somewhere to do that. Furthermore, this vac supply has to be isolated from the intake manifold itself, by a check valve and reservoir; otherwise every time the vacuum goes away, such as when giving the car some throttle, all the little doors will reset. The cruise control gets its vacuum from the same check valve/reservoir subsystem, for the same reason.
Since the HVAC system (and reservoir and all that) AREN'T part of "the engine", but rather of "the car", none of it is on the emissions hose routing diagram. Just as the cruise isn't. But that's what that line looks like to me.
thanks for such a detailed reply. It appears my hvac system is working correctly even with these disconnected however. The air channels all change over to what they should when engaged. Could it possibly be something else?
the 'air channels' changing over to what they should do indicates that the AC control head is receiving vacuum supply of some kind.
the 87 LG4 should also have a line off of the AC control head to a valve in the hot water line to the heater core that closes it when the AC is on. that's probably what you have in the first pic
the other line is likely for the EFE. it runs from the valve in the pass side exhaust manifold through a short section of flexible hose to a metal line that runs along the perimeter of the valve cover, to another short section of flexible hose to the EFE TVS (thermal vacuum switch) front of the intake manifold.
the 'air channels' changing over to what they should do indicates that the AC control head is receiving vacuum supply of some kind.
the 87 LG4 should also have a line off of the AC control head to a valve in the hot water line to the heater core that closes it when the AC is on. that's probably what you have in the first pic
the other line is likely for the EFE. it runs from the valve in the pass side exhaust manifold through a short section of flexible hose to a metal line that runs along the perimeter of the valve cover, to another short section of flexible hose to the EFE TVS (thermal vacuum switch) front of the intake manifold.
I think I have the EFE figured out but I can’t for the life of me figure out who this guy in the back is or where it goes.
And now I’m wondering if I had THIS hooked up wrong: this was on the bottom port of the TVS because I think I believed it was what the EFE was originally but now I’m thinking there wrong. Where do I go with this guy?
On my 87 TPI that rear plastic vacuum line runs uninterrupted along the firewall and Tees into a check valve in the vicinity of the wiper motor and brake booster. A rubber hose goes into the check valve from the cruise control/vacuum tank, and a rubber hose exits the check valve and goes to a port at the rear of the air plenum.
According to the diagram below from my 1987 Service Manual for the LG4, that plastic line looks like it would do the same: Tee into a check valve, with a rubber hose going into the check valve from the cruise/vacuum tank, and a rubber hose exiting the check valve going to a port in the carb. The image shows a cap on the check valve for a non-AC car; that's probably where your plastic line is supposed to connect. Yours is obviously too short to reach, but it doesn't look broken, so maybe it was cleanly cut? Do you see a check valve in the vicinity of the brake booster that looks like it might be missing a connection? Any rubber hoses laying around?
there should be a semi-hard line coming from the rear of the carb, into the ECM harness, then out to the vac sensor on the firewall 'behind' the brake booster.
the semi-hard, plastic line should have a rubber boot on each end that makes the connection.
Looks like there's a piece of vac line on your baro sensor (the thing with the blue connector right above the trans dipstick). There should not be. It's supposed to be exposed to the atmosphere, to measure ambient pressure.
The line behind the EGR solenoid tees into a check valve which then splits between the carburetor and the hard line behind the driver's side firewall. The bottom port of the TCS goes to the passenger side exhaust manifold and everything seems to be in place. Except my cruise control doesn't work but that's probably a whole different issue since I can't remember the last time it did.
07-14-2023, 02:43 PM
