What would cause my idle to rev up and down when parked, or stopped

Tiny
CIVICNOOB
  • MEMBER
  • 1986 HONDA CIVIC
  • 180,538 MILES
Ok so I had a bad radiator. I replaced that, I had to take off the coolant hoses attached to the radiator and to the engine. Replaced those hoses as well. But now when I start my car it does fine but once it heats up a little, the idle revs up and down. This is when I'm parked or stopped at a light. I think it could be my vacuum lines, but I think their could be more than just that. Suggestions? Thanks oh and I just donated again on an older post of mine, didn't know it wasn't going to give me a new? When I donated. Lol.
Thursday, May 31st, 2012 AT 1:12 PM

5 Replies

Tiny
FIXITMR
  • MECHANIC
  • 9,990 POSTS
That's an old car! Got a carburetor? Complex little bugger. So you say it did NOT have this trouble before radiator issue?
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Thursday, May 31st, 2012 AT 1:40 PM
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
Check the coolant level. Ensure coolant hoses to throttle body and Fast Idle thermo Valve are not clogged.
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Thursday, May 31st, 2012 AT 3:29 PM
Tiny
CIVICNOOB
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  • 7 POSTS
Correct it did not have this issue before the radiator was replaced. And I replaced hoses so they couldn't be clogged as for the throttle body its self, I'll check. Now where would the fast idle thermo valve be?
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Thursday, May 31st, 2012 AT 5:10 PM
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
This is a very old version so I can't recall the exact location.

It should be under the throttle body or somewhere nearby. Look for a cylindrical component on the intake manifold with a cap held by 2 screws and has 2 hoses at the bottom.

Btw check the idling speed, if it is too high, surging would occur. So would leaking vacuum hoses, check for any that is dislodged.
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Thursday, May 31st, 2012 AT 5:20 PM
Tiny
CIVICNOOB
  • MEMBER
  • 7 POSTS
Ok I looked for loose hoses. I found one its attached to what I'm guessing is my air control unit on the distributor. And the piece the hose attaches to it is loose. I'll check the other thing you were talking about. I do know that on my intake manifold to my fuel injectors has two parts that require two bolts to hold it. I'll look at those to see if I have hoses attached to. If I. Find it what should I do. As for the part that's loose. I'm going to jb weld it to get it to hold, and zip tie the hose to it till I can get the new part.
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Thursday, May 31st, 2012 AT 5:34 PM

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