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3rd Gen 1986 Civic base 1.3 with vacuum and idling problems

Old 04-29-2019, 06:00 PM
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Default 3rd Gen 1986 Civic base 1.3 with vacuum and idling problems

Hello all - I have a few questions and I'm hoping someone out there might be able to answer. First off, I am not super knowledgeable when it comes to engines, cars, etc. but I do know a little bit so please excuse any stupid questions or statements.
I have a 1986 Civic base model 1.3L hatchback that has been having some odd idling problems that may be connected to some vacuum line problem(s). Initially, my problem was seemingly just a VERY high idling situation, but got more complicated the deeper I dug. To try to keep this as simple as possible, I thought just listing the problems would be best.

1 - Very high idle (approx 1800+ rpm) that doesn't decrease
2 - Problem 1 was partially solved when it was discovered that the vacuum line to the carb was sucking way too much air
3 - Disconnected the vacuum line and idle was a bit lower, but still high above normal (1100 rpm? - sorry, I don't have a tach)
4 - Idle speed now varies with no apparent rhyme or reason, but usually stays too high with very occasional periods of normal speeds.

**- I should mention that this problem seemed to start around the same time I tried pouring some Seafoam into my carb in an effort to clean it out. Could the discharge of the dirty material (carbon?) have collected into the vacuum system? If so, could it gum up and/or block any valves/diaphragms? Specifically the one connected to the carb vacuum line?

I spoke to a guy at my local dealership and he suggested opening the vacuum control box where all of the vacuum lines go into and take out and clean all of the valves, diaphragms, etc. This seems to make sense to me since 1 or more of the lines lead to a problem. I haven't tried this yet as it is a bit outside of my experience but I would feel fairly comfortable doing it if it was the most likely solution. Would a stuck/gummed up/faulty vacuum diaphragm potentially cause the idle variation?

Again, sorry if this doesn't make a lot of sense due to my lack of mechanical knowledge, but it's the best way I know to describe the situation.

Any help would be GREATLY appreciated!

Last edited by crowbartexas; 04-30-2019 at 12:45 PM.
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