Jump to content
Ultimate Subaru Message Board

Zeroing in on a vacuum leak...


Recommended Posts

OK, this was a new one for me - might help someone else.

 

My '87 gl 3-door has been on the road for a few months but has had an intermittent idle problem that has baffled me.

 

Started the car today and it idled fine; decided to cycle the ac on, let it run cold for about 5 minutes, hit defrost and the idle goes really low, rev it up and then cycle through heat, defrost, bilevel, ac, off and defrost boggs it down each time.

 

Guess I'll be avoiding defrost and pulling the dash after it warms up.

Link to comment
Share on other sites

You may well be able to access the switch without pulling the entire dash. I know I removed one from a car in a boneyard not too long ago.. I have yet to install it into my car, however, so I can REALLY make any promises. :rolleyes: It seemed like it shouldn't be impossible, though.

 

The switch switches vacuum instead of electricity, and it is supplied by a line coming off the intake manifold, into a small white accumulator canister at the rear passenger's side of the engine bay.. from there, along the back of the engine bay and into the cabin, under the dash.

 

Since you only have a problem on "defrost" I guess it is safe to assume that the rest of the system is OK, and the "defrost" circuit somehow opens this vacuum up to atmosphere, causing a vacuum leak. However, you might want to find this line supplying vacuum to the white accumulator canister, and try removing it and plugging the end with your finger, while the engine is running; If the engine idles better than it normally does with your finger plugging the line off, there may be issues elsewhere in the entire apparatus, as well.

 

Feel free to post any further questions, I am not going into any more detail immediately. It sounds like you've got the issue under control. :grin:

Link to comment
Share on other sites

It's probably the AC idle-up not working.

 

It's is carbed? There's an idle-up solenoid that flicks the throttle up a degree or so to increase idle speed. When the defrost is on, the AC runs to dry the air, and to cycle the AC compressor oil through the system. When you hit the AC button, it's probably too cold out right now for the AC to kick on (it's about 25 degrees here). But it WILL run in defrost - that's normal.

 

If it's SPFI, then the AC idle up is a function of the ECU - there's a signal line that turns it on, and increases idle speed.

 

GD

Link to comment
Share on other sites

My spfi did same thing. Exactly what GD described it to do. In the cool, it got sticky, didn't want to idle up. Defrost has ac pump kicking in, but if heat set to warm, you don't get a/c. In regular a/c mode you could wait it out.. but I also found that it needed warmer weather for that high idle to function as well. Mine only worked in rather warm 70 degrees or above. There may be other ingredients to kick that in thermally raleated, I never bothered as the car kept running.

As for vacuum leak... if all is functioning on the heater box though the different openings getting air accordingly, I would guess there isn't one. The ea82 and vacuum leak is very very obvious. If a slo leak, fuel consumption and coughing once and awhile still reveals it obviously, nothing to hide (engine is too small to hide it).

The sroke of an ea82 is smaller than my pinky. :confused: everything has to be good.

Link to comment
Share on other sites

When you turn on the defrost or whenever the leak occurs go into your engine bay and spray brake parts cleaner on all of the vaccum lines and connectors between them... when your idle raises then youve found one of them... hehehe there will be more.

Link to comment
Share on other sites

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
 Share

×
×
  • Create New...