1998 Honda Accord High Idle

2012 HONDA ACCORD
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SPACENACHO
  • MEMBER
  • 2 POSTS
Hi,
I have a 98 accord with 245000 miles. When I start the car in idles fine for the first 5 minutes or so. Then when I hit the gas the car will idle between 3900 and 4000 rpm. Alternating back and forth between the two. If I tap the gas sometimes the car will back down to 3500 and maybe once it dropped to 2500. Also the temperature gauge doesn't move much but when I turn it off there is boiling coolant flowing back into the coolant resevoir.
Thanks
Dec 7, 2006 at 8:14 AM
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BRUCE HUNT
  • ✓Experienced Mechanic
  • 3,754 POSTS
That is way to high. Are you sure that the cable for the foot pedal is not sticking?
Dec 7, 2006 at 3:33 PM
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SPACENACHO
  • MEMBER
  • 2 POSTS
No, it's not sticking. Today I held the choke closed all the way and it did the same thing. It's acually jumping between 3750-4000 not 3900-4000 like I said earlier. But when it does it on its own the choke doesn't appear to close all the way.
There are two vacuum lines that go from some kind of valve or sensor just on the cold side of the thermostat up to the carberator. I don't know what it is but maybe if the thermostat is bad that is causing it?
Dec 8, 2006 at 7:52 AM
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DUCK95
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You said that you temp gauge isn't moving? A faulty coolant sensor will affect your idle. I would check/replace that first then make sure your thermostat is working. Also, there may be a FITV (fast idle thermal valve) and a IACV (idle air control valve) on your throttle body, these can become clogged, dirty, ect. Take them off and clean them. This will probably help.
Dec 13, 2006 at 8:48 AM
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Suggested Repair

Check and replace the coolant temperature sensor first, then confirm the thermostat opens properly. Remove and clean the FITV and IACV on the throttle body, and recheck that the throttle cable is not sticking.

Conversation Summary

A 1998 Honda Accord with high mileage idles normally for a few minutes, then jumps between about 3750 and 4000 rpm. The temperature gauge barely moves, and boiling coolant returns to the reservoir after shutdown. The owner ruled out a sticking throttle cable and noted vacuum lines near the thermostat and carburetor. Advice was to check the coolant sensor first, verify the thermostat, and clean the FITV and IACV.

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