1984 Subaru Legacy - need smog test help

I own a 1984 Subaru GL 4WD wagon. It is to a Legacy but that’s what I put for model since mine was not listed. Here in CA it will not pass the smog test, specifically the 25mph speed test on the dyno. When on the dyno it stalls at the 25mph test, but on the road it does not stall at any speed. My mechanic has done everything possible but to no avail: fuel filter and pump are working properly, plugs have been changed, and a new catalytic convertor installed.

Tell us what part is failing

Exactly which emissions are too high on the 25mph part of the test?

Better yet, post a picture of the smog results

There are a few smog techs on this website, and we’ll be glad to help you

Can I assume this is a stick shift?

Something just occurred to me . . . can you even put your vehicle into 2wd mode?

If not, it shouldn’t even be subjected to a dyno smog . . . in that case, it should be subjected to a 2 speed idle smog test

It doesn’t appear that any one part is failing. I initially took the car to my mechanic to take care of a rattle under the driver’s side, which turned out that the catalytic convertor needed replacing. My mechanic then had it checked out for smog (not an official test) and the problem was that on the 25mph test on the dyno the engine would stall. So they replaced two bad spark plugs, replaced the distributor, and checked the fuel filter/pump. Everything seemed to be working fine and no stalling when the vehicle is on the road. It only stalls when it’s on the dyno at the 25mph test. The emissions are fine at the 15mph test and would be fine at the 25mph test if the engine didn’t stall, even when there’s pedal applied to maintain the 25mph it stalls. Perhaps it’s a stricter dyno setting for the 25mph test? And yes, this is a stick shift, 4WD and FWD. I do not have emissions results.



Might be a fuel problem . . . but that’s just a guess


I’ve had a bit of experience with these models They use an EEC carbureted engine.

There were issues back in the day with what was called the ASV, or Air Suctioning Valves. There’s one on each side of the engine and feed into the carburetor. Over time these valves would heavily soot the top of the carburetor up and cause poor running and/or problems with the choke plate which could lead to stalling.

Remove the top of the air cleaner housing and see how sooted up the carburetor air horn is.

These were under Recall back in the day but after this many years good luck on getting that done (assuming it hsn’t been done previously…) because there probably isn’t an ASV on the planet. That may not be the issue; just pointing out a what-if.

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Thank you for your suggestion and I’ll check with my mechanic.


Thanks for the various suggestions for the Subaru. I spoke with my mechanic (again) and he said the carburetor was rebuilt several years ago, and the gas tank was refilled. Two years ago this car passed the smog test with the two speed dyno requirements. Since then, nothing has changed with the engine. However, he maintains that the dyno test is imposing an additional load on the higher speed test and thus causing the engine to stall. In Santa Clara County (CA) the smog tests are more rigorous than in other counties, and at the moment my only recourse would be to see if I could get the car smog tested in a less restrictive county.