99 civic high idle

  • Manstink1
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2 months 4 weeks ago #201146 by Manstink1
99 civic high idle was created by Manstink1
Hi, I have a 99 civic lx 4 speed auto. Recently rebuilt the engine and upon first startup the engine idles at 6000rpm. There are no intake leaks and the throttle is not being held open.
When I put my hand on the throttle body Intake theres a good amount of suction and pulls my hand nearly Into it. When I block off the intake hole completely the car stalls. Not sure how to proceed with my diagnosis of the issue, help is greatly appreciated :)

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2 months 4 weeks ago - 2 months 4 weeks ago #201148 by Tods213
Replied by Tods213 on topic 99 civic high idle
You need quite a bit of air to get to 6000 rpm. There are few thoughts that come to mind.
Civics have used a few different throttle bodies over the years. Fel-Pro engine kits don't come with all the correct ones sometimes. I had a 95 civic where I installed the wrong gasket and it would idle between 2 and 4k rpms. There was about an inch gap in the gasket sealing surface in that case. I think that was the most stable I could make the idle with the adjustment screw turned all the way in.
I'd start with an inspection of the t-body gasket. Lay it against the manifold and t-body during the inspection. It should surround the primary and secondary ports. If the gasket checks out, you could try duct taping the throttle nearly closed and try to find the air admittance point that way.
Best of luck!
Last edit: 2 months 4 weeks ago by Tods213.

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2 months 3 weeks ago #201207 by relative4
Replied by relative4 on topic 99 civic high idle
If an air leak is a candidate, then a smoke test is a great starting point.

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