I am trying to find out what the differences there are in the Idle Air Control valve from one year(84) to the next(85). I know that the length and pintal shape are critical to close off the by-pass correctly. But i want to know if there is a difference in the stepper signals? Are the signals changed by voltage or number of pulses to a given length of travel? What i am working on is an exact looking copy of the throttle body on 84 Corvettes but can't find answers on how to replace an 84 IAC that even the GM dealers can't find a replacement for. Will changing the IAC to a similar one work or will it require a new ECM or Chip?
Thank-you for helping,
Todd F.

 

Is there some thing wrong with using the GM 17078832 (A.C. Delco 217-406) part number called for?
The procedure is well covered in the 1984 FSM, but it is no different for an '84 than any of the other Corvette IACs. Lefty loosey, and righty tighty. Don't forget to retract the pintle before you screw it back into the TB.

RACE ON!!!

 

CFI-EFI,

You are just the guy i need to answer this puzzle... I am sorry that i am using the Corvette Forum to get an answer on a non-Vette...But no-one on the fiero forum seems to have any clue on ecm functions. The TB on my 84 fiero is identical to the TBs(Main one any-way) on my 84 Corvette. My problem is that i can't find an IAC for 84 and they only list ones for 85up. The engine was from an 85. When i installed the engine i found that the ecm would not run it untill i put the 84 TB assembly in it. Now i am thinking that i may have to use an 85 ecm. But i don't know if the different ecms run different values to make the various sensors, switches and/or injectors function.
Thus i am back to my question...Do different ecms run different signals to match certain IACs? Or are the IACs all operated with the same signals and the only change was in length and/or pintal shape?

 

I think I understand the question, but I don't have enough specific knowledge of ECMs to give you an answer. The parts numbers I gave you are listed to fit 1982 and 1984, Corvettes, only. Delco doesn't even to show these numbers to fit the Crossfire F bodies, let alone a Fiero. I expect they would work in a broader application than they are listed for, but any guess I might make would be merely idle speculation.

For a 1984 Fiero with a VIN code "R" engine, use a Delco 217-405 IAC. For a 1985 Fiero with a VIN code "R" engine use a Delco 217-437 IAC.

RACE ON!!!

 

That is what I am trying to do too.
I wish that i could get the thing to run long enough to put my Diacom on it to verify that the IAC is the problem. I need this stupid little car for making money. I hate using my 84Vette, it is gettting messed up from start & stop and dragging stuff in and out of the back. To top it off some-one hit and ran the right rear quarterpanel Wedensday night .
Is there any-one who burns chips that might know if there are different stepper signal types in various years. I would realy be behind if i spent a week hacking and splicing in an ECM to find out it won't work.
Thanks for trying.

CFI-EFI, I tried ordering the 217-405 thru local but it is not correct either (@ $127+ you would think it would be). It is the 4cyl. I also had an 86 6cyl which uses ALOT of the same parts as my 87Vette. You would think that some-thing would match up.

 

If I understand you correctly you're just trying to figure out if you need to change the signals coming from the ECM to drive the IAC motor. I don't believe there should be a problem. Every ECM I've looked at uses the same signal pattern (with differently phased signals to the windings to run the pintle in or out). I'm currently using an early 90's two barrel 454 TBI on my '84. My only modification for the IAC change was making a short cable to adapt the different connector configuration. Just for amusement, I also put a one barrel TBI (and ECM) on my dad's 1937 John Deere tractor after he wanted to make it run better than it did with the stock carb. I mixed and matched parts from different GM vehicles and didn't have to modify any hardware or software to accomodate the IAC (I did have to modify all the VE and spark calibration tables though).
In a nutshell, every IAC motor I've seen is just a two winding stepper motor. The ECM will output 255 signal steps at shutdown to guarantee that the pintle has completely closed, and then it will reverse the pintle direction a calibrated number of steps to allow the engine to start without depressing the pedal a bit. All in all, you should be able to find an IAC off another vehicle (junkyard perhaps) that will have the same connector size and insertion threads to minimize the work you need to do to get your car running.

 

The 217-405 is for the 1984. Since the engine in your '84 is an '85, could that be the reason the IAC didn't fit? Are both your car and the '85 engine VIN code "R"

RACE ON!!!

 

Since i had to put the 84 throttle body on to make it run(which it did great for 6yrs)it has the 84 TPS, Injector, MAP & IAC. I am just afraid that i will have to change all of those to switch to 85 ECM. It figures that i threw out the old TB (& a whole lot of other old stuff) this last winter while cleaning the garage to make room for working on my 87 Vette.
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.
The Vin code R was used on all 2.5L 4cyl.

 

I think that we are on the same page...When you say,What does the different phasing equate to in the actual running in and out of the pintal? Does a different phase equate to a different amount of length that pintal is pushed for each step or some-thing else?

 

Steppers with four wires really should all act the same. The connections are for the 84, outer two pins one winding, inner two pins the other winding. You can reverse the rotation just by swapping the two wires of a winding, doen´t matter wich winding, the inner or the outer two wires. I think that you should not expect other electrical problems other than the rotation direction.
I don´t really think that the car should lean when the IAC does not close completely, just maybe when cold. That you have to ask around. The car just should idle faster and you will have problems with the minimum air adjustment because, as soon as you pull the plugs out of the air bleed holes, the IAC motors may not be able to adjust low enough to set the idel low.
The AFR is set by the oxygen sensor (When in closed loop).

 

Thank-you Nico,

I am out looking at other areas now and am fairly shure that this should not be an issue and saves me from switching ECMs.
?????Now what??????

 

Hey Todd how are you. Long time no hear. Get rid of those fiero's and buy a real car!! Still building Lambo's??

Mal

 

MAL,

Hope you respond. Actually just spent 4yrs on my house and my mom's house. Completely gutted hers and you saw pics of the second story on mine before it was done. Now i am desperatly trying to get my 87 Vette done. I am almost ready to send it to paint, if i can get 6K+ for it. Actually i will be trying to start it as soon as i get the fiero running. Would have had it done this week if i hadn't had this pop up. So the Lambos haven't had a wrench on them since early 01. So what more do you want...I can only do so much...The 87 probably would have been done a couple months ago if i weren't so a-retentive about it and forgot how every-thing goes together. What hurt was putting water in it last month and found that the pretty polished water pump leeks worst than you after 2 pitchers. So every-thing came apart and goes slowly back together. Are you ever coming out this way again? I'll buy the beer!

 

No plans to go that way in the foreseable future. Anyway finally blew the engine in the 91. Local machine shop building a 500 hp 383 for me now. Can't wait to get it late August. Long line waiting. Recently )last summer) got a V8 Corvair. Still have 87 Vette Conv. Also a 2002 T-bird. Did you ever sell your mom's house? How is your eyesight?? See ya.

Mal

 

Todd,

Just to let you know a local small time used car lot here by my house has a lambo kit on a fiero chassis. Can send digital pics of ya want.

Mal

 

The house has turned into a LOOONG leagal nightmare....I don't really want to get into it right now.
I am just trying to finnish up the 87 Vette and the Prova Countach before i go totally blind, ie my eye is fading again(left one, the right is long dead). PM me or email me at todd_vette@hotmail.com I am about to close my highstream mail the end of the month. The phone # is still the same. I hope the 91 engine comes out great to match the body.
Take care.
if you get a chance check out below...still need body done and painted, interior comes after that.
http://todd-vette.tripod.com/mycarpics/