this post was submitted on 13 Oct 2025
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Mechanic Advice

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90's EGR Systems (lemmy.world)
submitted 4 months ago by Fuckfuckmyfuckingass@lemmy.world to c/mechanicadvice@lemmy.world
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Anybody know anything about 90's vacuum controlled EGR systems? I've got one of those goofy little Japanese import trucks, and finding info about how it's supposed to work is a nightmare.

There's a pretty good vacuum leak out of the top of the vacuum amplifier/signal doodad. Kinda UFO shaped deal between the vacuum advance, intake manifold and the canister.

Any ideas on diagnosis, or ways I can figure out what's doing what would be helpful.

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[–] Fuckfuckmyfuckingass@lemmy.world 1 points 4 months ago

My main leak is coming out the top of this thing, which I think I've ID'd as a vacuum amplifier. It's plumbed from the intake manifold on the bottom and runs between the vacuum advance and the charcoal canister. From what I remember it holds a vacuum on the bottom but doesn't seem to stop the flow of anything between. There's used ones on eBay, but I doubt they're in much better shape.

I'm tempted to try and pry the top off of it and see if I can glue it back into functioning, although part of me wonders if it's supposed to purge air out of the top.

The vacuum advance pod is pretty weird too. It's got two diaphragms stacked on top of one another. One advances the distributor and the other I'm guessing signals back to the system that the advance is on. Not sure if that part is working as that pod doesn't hold vacuum, but maybe it would if the advance was pressurized? I haven't figured out how to test that yet, maybe I'll apply vacuum to the advance and put a 2nd gauge on the signal one and see if it holds anything.