I have an '86 Duke that idles high on startup. Yes I replaced everything or I have cleaned it. All vac lines are good, cleaned EGR n put a new gasket on, checked brake booster line thing, complete tune-up two years ago, cleaned IAC, replaced CTS, fuel filter, air filter, thermostat, pcv valve. I may need to get new plugs but my wires look fine along with the distributor cap and what not. NOW I do notice a HIGH HISSING sound when I start the car cold about 2000-2300 RPM but i cannot tell where its coming from. Could it be an exhaust leak or still a vacuum leak?
thanks

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So now you'd better stop and rebuild all your ruins,
For peace and trust can win the day despite of all your losing

quote Originally posted by FIER086: I have an '86 Duke that idles high on startup. Yes I replaced everything or I have cleaned it. All vac lines are good, cleaned EGR n put a new gasket on, checked brake booster line thing, complete tune-up two years ago, cleaned IAC, replaced CTS, fuel filter, air filter, thermostat, pcv valve. I may need to get new plugs but my wires look fine along with the distributor cap and what not. NOW I do notice a HIGH HISSING sound when I start the car cold about 2000-2300 RPM but i cannot tell where its coming from. Could it be an exhaust leak or still a vacuum leak? thanks

I have never seen a Duke that did start up with a high idle and them work its way down.

Duke's are notorious for high idle... but if you hear hissing, chances are something is leaking and you will never get rid of your high idle with a vacuum leak. I wouldn't think that an exhaust leak could cause high idle though.

Have you rebuilt your throttle body yet? Autozone sells a rebuild kit for $33 that includes new gaskets and o-rings. If you have replaced everything else.....

Yes, I do need to rebuild the Throttle Body thank you for reminding me Hudini, but I can still hear a hissing sound on start up so I dont know if that will fix the problem.

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So now you'd better stop and rebuild all your ruins,
For peace and trust can win the day despite of all your losing

what causes a hunting idle

1100 - 1000 back and forth every second, sometimes down to 950 or 900
but then back up to 1100, every second 100rpm up and down over and over

i've replaced egr tube, checked egr valve,
and waved a propane tank over the lines
and found no vacuum leak

idle screw has not been uncapped

electronics?

[This message has been edited by Kuta (edited 04-21-2008).]

Here is the thread on the infamous hunting idle. On page 3 (3rd post from bottom) Dodgerunner said he changed a value in his PROM that got rid of his hunting idle. Seems if the ECM is programmed with a quick reaction time for the idle then it can swing back and forth causing the hunting. Anyway, check it out if you want: //www.fiero.nl/forum/F...2/HTML/077235-3.html

o.k. thanks i will read through that,
and whatever links in that thread too
(eg: Ultimate Meter Guide, Part 1 - 3)

My 84 2.5l Indy had a huge idle issue. It would race like mad and rarely drop to a normal level. For the longest time it did not code. But finally it codes for the coolant sensor. I replaced it. The idle evened out. Then the racing came back. Shortly there after the car coded again for the coolant sensor. Again I replaced it and it fixed the problem.

For the hissing. One trick you can try is to use a bit of seafoam to make the engine smoke. If tou have a leak in the exhaust the smoke will come out of the leak. I used this trick on my 2.8L firebird and Chevy dually when the exhaust hiss would show up and we could not determine if it was the mainfold to head or the donut gasket. I pinpointed and EGR leak on the bird this way.

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"I'm just a girl..."
1984 Indy Fiero Pace Car
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1982 Trans AM / 1990 Chevy Dually / 1976 Scout II / 1987 Nissan Pulsar