I am having trouble finding an Idle Air Control solinoid/valve for my 84 4cyl. Is there any source for just this year? I have had several shops order several diferent types but NOTHING matches what came out??????? The one that came out has about 12tight turns of spring and 3 dif angles on the pintel while most i have seen from orders have 3-4 turns of spring(much lighter spring also) and 1 or 2 angles on pintal???? What gives? Even local Pontiac dealer was mystified on why he could'nt find a listing for 84. Maybe this is not my problem? I was almost home when the engine started stumbling and stalled out but restarted in a very erradic idle forcing me to keep stabbing the pedal just keep it running. It died as soon as i got it parked and would not start again. Pulled codes and got 13, 34, & 35. Since then i replaced the fuel filter(Presure at almost 14psi after change), spark-plugs & wires, dist.cap & rotor, O2 sensor and air filter. This resulted in it starting again but would not idle and died. I have tried several IACs (one that cost twice norm and the ones from my 84 and 87 Vettes as well as an 85Fiero) but no change except won't start again. The IAC that i removed is totally frozen, can't turn or compress it. When i installed the engine it was from an 85 (wrecked) that i bought very cheep for parts since it had 28k miles and was running great. When it was first installed i found that the ecm would not run it so i switched out the throttle body for the original 84. In 7-8yrs it has run great and only the Fuel Pressure regulator needed replaced a year and a half ago. Please help. I am at a loss as to what else to try...My last idea is to try to adapt an 85 ECM that can run the the IAC right. Is there another option? Thank-you for looking in, I hope that some-one else has had an 84 IAC go out and found a replacement solution. Thanks Again, Todd F.
[This message has been edited by todd_vette (edited 06-10-2006).]
Hello, and welcome to the forum! The idle air control valve on the 84 Fiero is the same as the one used on other 300 series throttle bodies (Fieros from 84-86 and some other pre-87 GM cars). According to my 84 factory service manual, the distancefrom the main body of the idle air control valve to the tip of the cone should be no greater than 28mm (1-1/8 inches). There should also be an o-ring gasket between it and the TBI body. After the engine is started and reaches operating temperature, after the car has been driven over 35mph the ECM will reset the idle speed. The sensor itself should be tightened to 13 lf-lbs.
Swapping in an ECM from an 85+ Fiero will not work, because most of the 84's interior wiring is different from the later years.
There is also an idle speed adjust crew, but it is adjusted from the factory and should never be touched again, and is covered wth a plug. Might want to see if someone messed with it.
The cap is still intact over the idle adj. screw. Any good ideas as to if it is the IAC or some-thing else? The car ran fine for years then in a few seconds stumdled to death. Is there any way to find out if the 84 ecm uses different signals to the IAC from the 85+? Is there a GOOD source for wiring diagrams on the net for 84 and 85? How do you test the IAC on the Fiero? What tests can i do on the injector also? Please remember that i am more used to tpi. Thanks, Todd F.
[This message has been edited by todd_vette (edited 06-10-2006).]
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09:49 PM
befarrer Member
Posts: 1962 From: Westlock, Alberta, CANADA Registered: Aug 2002
Any ECM from 84-85 will work in an 84 Fiero, I have an 85 auto ECM in my Fiero, and my dad has an 86 5-speed ECM in his 84 Fiero that he put an isuzu in. 87-88 wont work because of the DIS. The only issue I can see is that if your car is a standard, and you put in an 85 or 86 ECM, then you will always have a shift light on because 85+ 2.5's had 5 speeds.
------------------ 84 Fiero Sport Coupe #1192 :: 86 Fiero Base Coupe Quad 4 HO :: 84 Chevette CS 4 Door 1.6L HO I got 2 HO's!!
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11:12 PM
Jun 11th, 2006
lurker Member
Posts: 12355 From: salisbury nc usa Registered: Feb 2002
Whats up with the 85 being 41.79 bucks & the 84 being 107.00 bucks
Code 13 Oxygen Sensor Failure When the ECM detects there's no variation in the voltage sent by the Oxygen Sensor during normal operation of the car, it wil set Code 13. Usually this means the sensor is disconnected or it needs to be replaced. Also check for a sticking or misadjusted Throttle Position Sensor.
Code 34 Manifold Absolute Pressure (MAP) Sensor The ECM will set code 34 when a problem with the MAP sensor is detected (unusual high vacuum/low pressure). Code 34 usually indicates a defective MAP sensor. Check all connections and replace the MAP sensor if necessary.
Code 35 Idle Speed Error The ECM will set code 35 when the engine speed is 75 RPM above or below the correct idle with closed throttle. This condition must be met for at least 45 seconds before the code is set. If idle speed is too high, check for vacuum leaks. If idle speed varies up and down, your engine might be running too lean (high air/fuel ratio). Check for low fuel pressure or water in fuel. If idle speed is too low, your engine might be running too rich (low air/fuel ration). Check for high fuel pressure or leaking/sticking injectors. Also, check all connections to the IAC and replace the IAC if necessary.
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11:04 AM
todd_vette Junior Member
Posts: 9 From: Pueblo, Colorado, United States Registered: Jun 2006
Yeah, WHAT IS UP WITH THE PRICE?!?!?! I have bought both of the ones pictured (except that your 85 pic seems a little diferent pintal shape?) to the tune of $180+ local + tax. I did change the o2 sensor with no change(it was over-due to change any-way). All the wires have been checked and rechecked. I did find where i pinched off the EGR vacuum line when installing engine, but it has been like that for years, Why would it act up now? What is the resistance value on the injector? And what base line voltage is best for TPS in closed possition and WOT? I cant get it to run long enough to pull values with Diacomp lap-top testing.
Currently in car is the 85(from standard trans car) and the 84 throttle body. The 85 TB was incompatible with my 84 Auto trans. ECM (?WHY?). I tried the MAP from my 84 Vette on it already but this brought no change...I was even lazy and put the Fiero MAP on the Vette and it works. Any other ideas?
[This message has been edited by todd_vette (edited 06-11-2006).]
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08:22 PM
Jun 12th, 2006
todd_vette Junior Member
Posts: 9 From: Pueblo, Colorado, United States Registered: Jun 2006
I got it to run for about a minute today while playing with my Auto-XRay reader. Real strange that its showing faulty O2 sensor(I put new one in the other day) and flaged a lean sensor on it to boot???? The funny thing is that i was playing around switching out the pile of IACs i have collected this week...It started on the one from my 87Vette????? Since the Vette ones are shorter it makes sense that it was lean...The pintal couldn't close. It started on stepper # 128 and smoothed out some at #58-62(it was jumping fast around there). I wonder why the ecm didn't close it at a higher step number? I am realy wondering about the MAP so i will try to start it again and run a capture on the MAP maybe i will see something. I wasn't sure about getting .78volts from the TPS also(ran up to over 4volts when pedal pressed all th way). If the XRay is reading all this through the ECM doesn't that meen that the ECM is ok? I have to go back to work tonight and i REALLY don't want to take the Vette(it's been hurt enough)! I hope some-thing gives here. Any-body have any other ideas after the IAC???? What values should i be getting from TPS, and MAP? please fill me in. Thank-you.
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04:16 PM
Dec 20th, 2006
DMaxME Member
Posts: 184 From: Rochester, NY Registered: Dec 2006
My duke is giving me all kinds of crap, it origionally had some problems with running, untill i rebuilt the throttlebody and cleaned the injector. it ran fine for 100 miles, but now it has no idel, as in if i let off the throttle it dropps to stall, but i can hold the throttle and idle the engine smoothly at 800 rpm, the engine wants to be there, but i'm guessing the IAC is stuck or something. so this weekend i'll change it, hopefully thats the only problem
84 IAC motors are different from ALL OTHER fiero IAC motors, it may look the same, but they are different, my 84 duke with 39k miles never did run right, and gave me the IAC code, i tried IAC's from many different types of fiero's ive parted out over 20 fiero's finally i got a friend to send me a 84 IAC from a known good motor, popped it in and it worked fine, i hadnt parted any 84's out and therefor didnt have any 84 IAC's the price at rock auto is different because the 84's are much harder to find, i think the 2.5L S10 and camaro/firebird from 1982-1984 will work as well if they have a IAC, otherwise a citation may also work.
find a 84 model IAC, i may have one im not sure if my current 84 parts car has it or not, either way i cant test it cause the motor is bad.
