1985 Honda Prelude engine idle at startup

Tiny
JIM GARDNER4444
  • MEMBER
  • 1985 HONDA PRELUDE
  • 4 CYL
  • FWD
  • MANUAL
  • 18,000 MILES
My dual carb 1.8 runs great it doesn't like to maintain an idle when FIRST started up. After a minute or two no problem or on further start ups. JIm
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Sunday, August 9th, 2009 AT 10:56 PM

5 Replies

Tiny
KHLOW2008
  • EXPERT
Hi Jim,

If you depress the accelerator once and release before starting, does the engine runs well at initial startup?
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Friday, August 14th, 2009 AT 11:40 AM
Tiny
T.BRAU@HOTMAIL.COM
  • MEMBER
Thank you for responding. Yes the car will idle if I floor it for one second before starting. The car will stall out upon further throttle movement. So if I step on it for one second and start it it will idle (a bit high) if I just drive away without stopping for a few minutes all is well.
Thyank you for your time

Jim
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Friday, August 14th, 2009 AT 4:45 PM
Tiny
KHLOW2008
  • EXPERT
The problem is caused by a stuck or misadjusted throttle opener. When this happens, the throttle is not opened when engine is stopped and this would not allow the autochoke to come into action unless you have depressed the accelerator at least once..

Start engine and run till operating temp and with engine running, disconnect the throttle opener vacumn hose ( blue arrow ) and plug it. Engine idling should incrase to at least 1500 rpm, if it does not, adjust the throttle opener adjustment screw till the desired rpm is achieved.

Vacumn test the throttle opener diaphragm for leakages.


http://www.2carpros.com/forum/automotive_pictures/192750_Carb84Prelude_1.jpg

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Saturday, August 15th, 2009 AT 7:03 AM
Tiny
T.BRAU@HOTMAIL.COM
  • MEMBER
THANK YOU ever so much. I was going to look in the choke area ( if I could find it!) I see the part in your picture (thanks again) so I will try your fix in a few days or next week. I am a student studying automotive technology at contra costa college in san pablo CA not much attention to carbs so your input is great and I believe most likely the problem. Could this also cause a stumble of rpm's when using the brakes like coming to a stop and holding the brake down?

Any way thank you so much again Brau
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Monday, August 17th, 2009 AT 5:20 PM
Tiny
KHLOW2008
  • EXPERT
You are welcomed.

No, the stumbling when holding the brakes should be a vacumn leak associated with the brake booster.

In between the brake master cylinder and booster there is a seal and when this seal is bad, holding the brakes would cause vacumn leaks and the engine to stumble.

Remove the master cylinder holding nuts ( hydraulic pipes need not be disconnected if space is available ) and slowly pull the master cylinder sufficiently to enable you to get at the seal.
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Monday, August 17th, 2009 AT 6:39 PM

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