crowbartexas

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!

letank

a bit late, but with my experience time to see if you do not have another vacuum leak... there is a big hose under the intake manifold, you need to jack up the car, put blocks under the wheel or serious ramps, never trust a jack to hold up a car while you crawl under it... too many people have died crushed by their vehicle.

the air box is usually fairly reliable, recheck the carb to intake manifold nuts... that gasket is impossible to get, it has some water passages

good luck

crowbartexas

Thanks for your reply!! I'll be looking into this ASAP.

TinaCarmina

TinaCarmina

My 86 Civic Si has the same problem though never idled that high. Same partial solution re idle but settles into "voom voom voom" surging idle *after* warmed up so IAC valve could also be the problem, I'm going to have that checked/cleaned/reconditioned/whatever is necessary along with the vacuum hoses. Does your variable idle happen before or after the car warms up? Two different problems.

This is a couple of months after your post - did you solve the problem?