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Can an exhaust leak cause high idle?? by FIER086
Started on: 04-16-2008 10:03 PM
Replies: 8
Last post by: redraif on 04-23-2008 03:26 PM
FIER086
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Report this Post04-16-2008 10:03 PM Click Here to See the Profile for FIER086Send a Private Message to FIER086Direct Link to This Post
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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MstangsBware
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Report this Post04-16-2008 10:49 PM Click Here to See the Profile for MstangsBwareClick Here to Email MstangsBwareSend a Private Message to MstangsBwareDirect Link to This Post
 
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.
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jscott1
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Report this Post04-17-2008 12:08 AM Click Here to See the Profile for jscott1Send a Private Message to jscott1Direct Link to This Post
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.

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Hudini
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Report this Post04-17-2008 08:47 AM Click Here to See the Profile for HudiniClick Here to Email HudiniSend a Private Message to HudiniDirect Link to This Post
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.....
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FIER086
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Report this Post04-18-2008 08:48 AM Click Here to See the Profile for FIER086Send a Private Message to FIER086Direct Link to This Post
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

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Kuta
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Report this Post04-18-2008 01:30 PM Click Here to See the Profile for KutaClick Here to visit Kuta's HomePageSend a Private Message to KutaDirect Link to This Post
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).]

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Hudini
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Report this Post04-19-2008 07:14 AM Click Here to See the Profile for HudiniClick Here to Email HudiniSend a Private Message to HudiniDirect Link to This Post
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: http://www.fiero.nl/forum/F...2/HTML/077235-3.html
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Kuta
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Report this Post04-21-2008 04:31 PM Click Here to See the Profile for KutaClick Here to visit Kuta's HomePageSend a Private Message to KutaDirect Link to This Post
o.k. thanks i will read through that,
and whatever links in that thread too
(eg: Ultimate Meter Guide, Part 1 - 3)
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redraif
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Report this Post04-23-2008 03:26 PM Click Here to See the Profile for redraifClick Here to Email redraifSend a Private Message to redraifDirect Link to This Post
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
1987 Red & Black Firebird: "RAIF" WEBSITE: www.redraif.com
OTHER CARSí WEBSITES:
1982 Trans AM / 1990 Chevy Dually / 1976 Scout II / 1987 Nissan Pulsar

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