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High idle until warmed up. by Dustinx22
Started on: 01-21-2013 02:45 PM
Replies: 19 (2173 views)
Last post by: theogre on 01-13-2014 12:32 PM
Dustinx22
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Report this Post01-21-2013 02:45 PM Click Here to See the Profile for Dustinx22Click Here to Email Dustinx22Send a Private Message to Dustinx22Edit/Delete MessageReply w/QuoteDirect Link to This Post
So i just bought my first fiero an 87 2.5 4cyl 5 speed. It was sitting for about 5 years so i got it running after changing all the fluids and other stuff such as plugs and wires new gas. So ever since I got it running ive had a problem with it idling to high after starting it up it idles around 2 grand until the engine is up to operating tempature. So my first thought was an vaccum leak. I have searched every inch of the intake for a leak and can not find one I have rebuilt the entire throttle body with new gaskets, put in an new idle air control motor, new thermostat, ect sensor and even a new pcm. So im baffled about what it could possibly be. If anyone has had this problem let me know some fixes it would be much apreciated. Thanks Dustin
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phonedawgz
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Report this Post01-21-2013 03:00 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
GM programmed the cold idle pretty high on the Fiero engines.

If your idle starts high when cold, and reduces to about 850 - 950 RPM when fully warmed up, that pretty much means the IAC, ECM and CTS are working right, or at least rightish. A non-functioning IAC would idle slower cold and higher warm. The ECM isn't really going to mess up the idle speed, if it is working. The CTS must be indicating to the ECM when the engine is cold, resulting in the cold idle, and once the engine warms, again must be reading rightish since the idle reduces. If you really want to know exactly what the ECM is doing you can get a scanner cable, and use TunerPro RT on a laptop to get the actual readings. Again, my guess is they are at least working about right. btw, I sell the scanner cables here - http://www.reddevilriver.com/aldl.html

TunerPro RT can be downloaded for free at tunerpro.net

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The solution if you really want to fix it
----

If you wish I can supply you with a reduced cold idle speed chip for your ECM.

http://www.reddevilriver.com/Related_Products.html

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Dustinx22
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Report this Post01-21-2013 03:17 PM Click Here to See the Profile for Dustinx22Click Here to Email Dustinx22Send a Private Message to Dustinx22Edit/Delete MessageReply w/QuoteDirect Link to This Post
The idle goes down to about 1100rpm when warmed up which I know is still high. I have the 2.5L 4cyl so I dont know if you make a chip for the 4cyl but the link is for a 6 cyl
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Gall757
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Report this Post01-21-2013 03:19 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Welcome to the Forum!

You still have a vacuum leak somewhere. Get the warm idle down to 900 and the cold idle will drop accordingly.

[This message has been edited by Gall757 (edited 01-21-2013).]

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Hudini
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Report this Post01-21-2013 08:43 PM Click Here to See the Profile for HudiniClick Here to Email HudiniSend a Private Message to HudiniEdit/Delete MessageReply w/QuoteDirect Link to This Post
Have you done the idle reset procedure? When I rebuilt my '87 TBI the instructions included directions to reset the idle.
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Dustinx22
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Report this Post01-22-2013 12:00 AM Click Here to See the Profile for Dustinx22Click Here to Email Dustinx22Send a Private Message to Dustinx22Edit/Delete MessageReply w/QuoteDirect Link to This Post
No i have not. The tbi instructions did not say anything about reseting the idle. how do i go about that?

[This message has been edited by Dustinx22 (edited 01-22-2013).]

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Hudini
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Report this Post01-22-2013 12:12 AM Click Here to See the Profile for HudiniClick Here to Email HudiniSend a Private Message to HudiniEdit/Delete MessageReply w/QuoteDirect Link to This Post
Jumper pins A&B on the ALDL port behind the cig lighter panel. Turn ignition key to ON but do not start. Walk back to engine and listen for "click, click, click" as IAC is driven fully closed. Wait 30 seconds then remove IAC electrical connector. Now walk back and turn ignition key to OFF. Remove jumper on pins A&B on ALDL port. Walk back and reconnect IAC electrical connector. Now the car should start and idle normally.

On my '87 when very cold it would idle very high for a minute or two then slowly idle down. The warmer it was outside the lower the cold idle upon start.
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Dustinx22
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Report this Post01-22-2013 12:28 AM Click Here to See the Profile for Dustinx22Click Here to Email Dustinx22Send a Private Message to Dustinx22Edit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks that is pretty much the same problem i have.
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Joseph Upson
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Report this Post01-22-2013 09:06 AM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonEdit/Delete MessageReply w/QuoteDirect Link to This Post
You'll still want to check into what phonedawgz mentioned and scan it for proper coolant temp sensor operation as the idle has a direct tie into that and if it's biased toward the low side it can cause a higher than normal idle. There's also the very real possibility that having sat for 5yrs and you not knowing the history prior to this that you have a failing tachometer that is reading several hundred rpm higher giving you the impression the engine is idling to high after warm up when it may be on point.
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Dustinx22
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Report this Post01-22-2013 11:40 AM Click Here to See the Profile for Dustinx22Click Here to Email Dustinx22Send a Private Message to Dustinx22Edit/Delete MessageReply w/QuoteDirect Link to This Post
The car has 36,000 miles so idk if the electronics are going.
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kev63rod
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Report this Post01-22-2013 09:40 PM Click Here to See the Profile for kev63rodClick Here to Email kev63rodSend a Private Message to kev63rodEdit/Delete MessageReply w/QuoteDirect Link to This Post
dont know if it makes you feel any better but my 87 2.5 will idle 2000-2200 when its cold but after it warms up it drops to 800 or so. it does take it a while to warm up. i searched all over for a vacuum leak but havent found one.
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FieroMaster88
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Report this Post01-22-2013 09:55 PM Click Here to See the Profile for FieroMaster88Click Here to Email FieroMaster88Send a Private Message to FieroMaster88Edit/Delete MessageReply w/QuoteDirect Link to This Post
The duke in my Indy idles high for a couple minutes on cold start. Actually every duke powered Fiero I've ever had has idled high cold.

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88 Coupe: 2.0L Turbo 4 Cylinder, W2A, T25 Turbo.
84 Indy #64: Restoration Project!

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Dustinx22
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Report this Post01-24-2013 02:23 PM Click Here to See the Profile for Dustinx22Click Here to Email Dustinx22Send a Private Message to Dustinx22Edit/Delete MessageReply w/QuoteDirect Link to This Post
Warm mine runs at about 1100 which is still high. I know. Any places the engines are know to get air leaks?
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bobace455
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Report this Post01-12-2014 10:06 AM Click Here to See the Profile for bobace455Send a Private Message to bobace455Edit/Delete MessageReply w/QuoteDirect Link to This Post
I am wondering as well. 2200 when cold and takes about 4 min of running that high before it will switch and go down to 800...pretty drastic change. it is the last think left to fix on it (86 2.5). TB is bolted down tight. Egr is unplugged because when it gets vacuum and is working the engine runs poorly- starts chugging. So I just plug the vacuum line to it. All new vac lines and tested canister and it is not leaking.
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georgie
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Report this Post01-12-2014 04:47 PM Click Here to See the Profile for georgieClick Here to Email georgieSend a Private Message to georgieEdit/Delete MessageReply w/QuoteDirect Link to This Post
The best way to find a vac leak, is to get a small hose that is 4 or 5 feet long an when your motor is running put one end to your ear and the other end move it all around your vac hose's an the motor you will hear any leak's on your motor! It work's an it's free or very cheap. Good luck
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theogre
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Report this Post01-12-2014 06:44 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
Cold start idle... 2000-2500 is normal weather is cold. ECM slows to normal after running a few minutes.
Even PROM TSB numbers does this.

If you have not drive the car then expect to have high idle.
If you have drive the car for 35mph 1-2 minute then You likely have vac leak

If idle screw is sealed then likely won't help fooling w/ screw.
Setting idle stop is only for replacement TBI, etc.
See my Cave, Idle Stop

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phonedawgz
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Report this Post01-12-2014 09:59 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
I could do a reduced cold idle speed chip for the 84 - 86 2.5 ECM but I don't have the definition for the 87 - 88. I am researching this however.

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LornesGT
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Report this Post01-12-2014 10:11 PM Click Here to See the Profile for LornesGTSend a Private Message to LornesGTEdit/Delete MessageReply w/QuoteDirect Link to This Post
I was think about buy that from you when things are put back together, but it also comes with EGR delete, right?
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phonedawgz
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Report this Post01-12-2014 10:51 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
After further review........

It looks like I can take care of the 87 - 88 2.5 ECMs also.

2.5 EGR valves are not controlled by the ECM so I can't just program out the EGR function of those years.

Hit me up if anyone is looking for a reduced idle PROM. - $55 shipped. Includes a new carrier for ECMs that have the PROM in a carrier.

[This message has been edited by phonedawgz (edited 01-12-2014).]

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theogre
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Report this Post01-13-2014 12:32 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
87+up
EGR is not Controlled by ECM but GM program Ignition timing to expects EGR flow and Engine can knock w/o a working EGR valve.

When cold is NORMAL to get high idle when ECT sees low coolant temp. 0°F and starting cold then expect 2000+ RPM when AT is Park/neutral or MT out of gear etc.
ECM is trying to make sure engine won't stall.
Should slow idle to ~1100 in a few minutes then to normal, ~900, when engine is warm.

Idle speed is 1000 RPM when ECM scan tool is attach. ECM can run w/ scanner but can affect Idle speed and other settings.

TSB on PROM...
See my Cave, PROM TSB notes
If you have high idle at odd times then maybe you need update PROM.
Most cases I've seen... Most high idle is vac leak etc.
New PROM versions can fix the knocking, mostly ~half throttle w/ some engine loads.
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