Bulldog92

iTrader: (1)

Take a look at the pic below...see the square-shaped, four-pin connector with the blue and green wires running to it? That is the plug that connected to my old 305 TBI on the rear passenger side of the TBI unit. I believe this is the IAC sensor. The 454 TBI unit (from a 1995 C3500 pickup) also has a four-pin connector, which is shown, but as you can see it is flat and completely different. Does anyone know the P/N for this connector and how to wire it up (i.e., where do the blue and green wires go?). I'm hoping somebody has this locally so I can fire this puppy up tonight...that 350 HO is just dyin' to run!

snflupigus

splice em

https://www.thirdgen.org/techbb2/sho...ight=iac+wires

you're not putting a 454 on a stock 305 are you...?

whats going to happen is... youre going to have lag off the line because the pumpshot for your injectors will be wrong for the amount of air now entering the the engine when you gun it off the line... then you'll be lean and get some knock counts... your computer will retard the timing, and your car will be slower. You will however hear an exhaust tone difference and your high rpm power will be increased. If you can have someone tune your prom again to compensate for the airflow changes you're car will love you, but untill then, stick with the small block tbi its more than enough for a stock 305.

ask me how i know this

wait... i read your post again... your sig is out of date isnt it 350ho what???? nevermind... have fun tuning, hope you have the tools..

good luck.

Bulldog92

iTrader: (1)

Sorry for the confusion...I've been converting my car over to a 350 HO/T56 for the past couple of weeks as time permits. I'll update my sig once it's actually running.

I read the thread you listed, but it looks like it was talking about a Holley 670cfm TB, not a 454 TB. I guess I'm a little confused...how can I splice into a connector I don't have? I think that the thread was talking about the IAC connector that comes with the Holley TB unit.

Oh, and I finally got in touch with a dealer and the GM part # for the IAC connector is 12085506 and it is $34.26...geez. I thought I saw an old thread where you (snuf) scoured a junkyard and found some of these IAC connectors. Got any left or any advice as to what cars had them? I'm really tired of spending big bucks for cheap little connectors (already paid $50 for two connectors on my T56!).

snflupigus

i have the female connectors that will plug dirrectly into your stock male iac connector... however, i do not have pins installed etc.. a gm tech could do it for about a buck if i sent you the plug. they have a delco connector kit, they are required to. Ill check to see if i have that plug.

Btw, the wires are the same on the holley.

However... i thought you had a 305. For a 350, its straight accross wiring. pin a-a, b-b etc... no swapping blues.

ill get back to you tonight. dont even think about spending 35 dollars for something that cost 2 bucks. tell that dealer to go ... well, you know.

Bulldog92

iTrader: (1)

Sweet...look forward to hearing back from ya

Bulldog92

iTrader: (1)

Well...I went ahead and bought the connector since I'm trying to get the engine running this weekend. Everyone, please note: 12085506 is NOT the right GM part number for the IAC connector on a 454 TBI. That is actually the connector for the 305 TBI that I already had. The GM catalog that the dealer has is not correct...it is supposed to be P/N 12126487 and the list price is $39.48, but you can get it for $19.74 + $7.95 S/H = $27.69 from www.gmpartsdirect.com if you're willing to wait about a week to get it.

So...now I need to know how to wire this puppy up. The GM connector comes with four white wires and I need to know what goes where. With the clip on the connector facing down, can someone tell me where the following wires go from left to right?

Green w/black stripe
Green w/white stripe
Blue w/black stripe
Blue w/white stripe

Any help will be much appreciated...thanks

snflupigus

Sorry I didnt get back to you in time. Like I said, I could have made you one for about 5 bucks. Im sorry, but it would have required a 35 minute drive there and back just to get the parts for connectors... if I was already going there I would have made one for you.

But here is how you wire it up...

On the connectors there are letters. These letters are molded into the plug on the side where the clip is.

blue w white stripe is A

blue w black stripe is B

Green w white stripe is C

Green w black stripe is D

Again, looking at the connector with the clip facing DOWN like you asked (which is not where the letters are)... & reading from left to right.........

grn w/ black
green w/ white
blue w/ black
blue w/ white

This is how you would wire it for a 350. For a 305 - you swap the A & B - (or blue wires).

Let us know how she turns out.

Again, sorry about getting back to you so slow. busy weekend... and i do not have a spare plug at my house from the junkyard - otherwise i would have sent em to you. But hey, whats another 35 bucks in a project that runs over 5 thousand?

Bulldog92

iTrader: (1)

THANKS!!!

Man, you are just in time...I'm about to head over to the warehouse and try and finish up my car. I will definitely let you know how it goes...thanks again.

PaulD

try whiteracing.com for the connectors at a much lower price than the General. If it isn't pictured, they got 'em anyway. I got my IAC and TPS connector there for my BB unit. Haven't put it in yet, though.

BMmonteSS

Would it be possible to just swap the 454 iac for a 305 iac since the conector is about as much as a sensor?

snflupigus

no. the mount is different. the sb tb has a screw in iac and the pintle is smaller. the bb tb has a iac that has 2 screws and an oring to seal it up - it doesnt screw in. the pintle on the tip of the plunger is also larger.

Bulldog92

iTrader: (1)

Yeah, I already thought about swapping the IACs...snuf's right...they are totally different.

Well, we fired the new 350 HO up last night with the 454 TBI. Man, you would NOT believe the Niagara Falls that was goin' on inside my throttle body, even at idle! I MUST have something wrong here...she was dumping so much fuel it was almost inconceivable. She's running REALLY rich. I now have **** on my ground effects from the break-in we did last night. I realize that I now have 80 lb/hr injectors with the 454 TBI, but I thought it would cut back at idle.

Here's what it does: I fire it up, it acts like it's going to idle OK for about 10 seconds, and then it revs up slightly on its own for a couple of seconds and dies.

This may all go back to my misunderstanding your IAC connector wiring instructions, snuf. I'm not familiar with the idle air controller, but I would guess that it attempts to monitor the air at idle, right? If so, sounds like my problem could definitely be attributable to hooking the IAC up wrong. Anyway, you said...

Did you mean this is how you would wire it if you NOW have a 350 or if you had a 350 in the first place (such as a Chevy truck)? I originally had a 305 TBI and have now swapped to a 350 HO with a 454 TBI on it. I didn't swap the A & B wires, but now I'm thinking I should have...should I? Let me know when you get a chance.

I'm about ready to slap on the old 305 TBI just to get the car out of my buddy's warehouse...man, I hope I don't have to do that...anyway, thanks for your help.

UPDATE: OK, I finally found an old post that talks about a problem similar to this. It appears that my stock L03 chip simply will not properly operate these massive injectors. I was hoping that the car would be functional with the stock chip, at least to the point that I could drive it about 1/2 a mile to my house. I was optimistic since JPrevost was able to use his stock chip at first, but he had a Holley TBI that has 65 lb/hr injectors, I believe. That may be the difference. I knew I would need to burn a new chip to get it optimized, but I was not aware that it was necessary to get it functioning at all. Anyone have any thoughts? I still think I have my IAC wired up wrong, though...

JPrevost

Unless you can lower the fuel pressure you'll be washing the cylinder walls. Modify the regulator to be adjustable and turn the pressure WAY down. Use winaldl to get you a nice light throttle BLM in the mid to high 120 range. That way you aren't overly rich but if you do rev quickly above peak torque you don't run it too lean. Better rich than lean (in most cases).
I was able to drive the car and motor 540 miles to break it in with the stock 305 calibration. It got great gas milage with those 3.08 gears in the rear .

Bulldog92

iTrader: (1)

Thanks for the advice, Jon...I'll go ahead and do the AFPR mod this afternoon and see what happens. I don't have a fuel pressure gauge, though...maybe I can pick one up at the local parts store. I just want to make sure I don't take the pressure TOO far down.

Do you think this will address my problem with the engine dying after 10 seconds @ idle, though? Let me know your thoughts on that one when you have another minute...thanks

snflupigus

i think that the swap is for the iac not because of main harness or ecm differences. dont swap em. i dont think that is it.

the iac does not monitor anything, it is not a sensor. it is a stepper motor. it does what the computer thinks needs done to adjust incoming air to match the fuel at idle. my guess is that your ecm cant even begin to adjust the air enough and was trying its hardest to get the fuel down instead...

you've entered the twilight zone, (constant tunning) Its going to be a while before this beast is running as smooth as it came from the factory. im sure jon will help you. this is now out of my league because i dont yet have the first hand experience in tuning a swapped 350 like he does. I've fallen behind by a year or so in this area now.

Bulldog92

iTrader: (1)

Thanks, snuf...I think you're right, it wasn't the IAC connection.

Here's what I ended up having to do. Jon, I took your advice on reducing the fuel pressure. I started going through the steps to convert the regulator so that it is adjustable, but I discovered that the 454 TBI regulator is very different from that of a 305 TBI. Check out the pic below...you can see that the 454 unit (on the left in the pic) doesn't have the tab coming out the side, there is no bung on top, and the spring is about twice as stiff as the one on the 305. I figured that this super-stiff spring in the 454 regulator was probably resulting in some seriously high fuel pressure, so I decided to change over to the 305 unit. I made it adjustable and cranked the fuel pressure way down by letting out on the spring quite a bit.

I threw everything back together, fired it up, no more idle problem. Jon, you da man. :hail:

I was able to drive it home, although I discovered I managed to foul a plug during this whole process because it was missin' like a big dog. Oh, well...that's an easy fix compared to everything else I've gone through in the past couple of weeks. One other thing...the hood doesn't fit, which I was expecting. I bought a drop-base air cleaner, but it won't seat properly due to the throttle linkage on the 454 TBI sticking too far out. I'm going to try to get that taken care of, try the drop base, and see if that gets me the height reduction I need to close the hood.

Of course, the next step is to start tunin'. I have already installed a 350 knock sensor and ESC module, so at least that's taken care of. Hmmmm...that may also have contributed to me giving the stock 305 bin fits (ha). I'll start with the ANLU bin as Jon recommended and go from there, I guess. Fortunately, I already have a chip burner at work...just got to figure out how to use the thing. I have already downloaded the GMECM software as well as several different bin files (along with the 6Ev010.ecu file that Jon created). Everybody seems to use TunerCat, though...maybe I should start with it instead. Anyway, I'm determined to get this car running well, so whatever it takes. I'm sure I'll be spending a lot of time on the PROM board now...

snflupigus

your next investment.... fuel pressure gauge - and aldl connector

Low C1500

If anyone is having trouble getting the IAC and TPS plugs to match there new throttlebodys, just go to any wreckers, Those style plug connectors are on most gm cars from late 80's to mid 90's. I got two sets and it cost me $5.

HarryJ

OK, I am confused a little...

I have '91 Caprice that HAD a TBI 305 and I am swapping in a '91 TBI 454. I ordered P/N 12126487 for the correct plug, but now I need to know how I wire it up.

THANKS!!

Low C1500

On your new plug the wires will be labled ABCD, then match the letters to your original wire colors.

HarryJ

Dang! GM P/N 12126487 is currently not available through General Motors, at least that is what gmpartsdirect.com told me today when I tried to order it.

Well, guess it is back to the boneyards.

snflupigus

again, i have the female ended plugs for where your stock iac would plug into... then you can wire on a new connector that goes INTO your new 454 iac - but i suggest just splicing unless you think you might put a stock one back on someday. LOL

Bulldog92

iTrader: (1)

HarryJ: I would try going to a local dealer for the connector if you can't locate one in a junkyard. They will likely be able to get one from a warehouse somewhere, but you'll just pay a little more for it.

rockinw

Howdy, I have installed a new GMPP HT 383 in my 93 Suburban. I have a Holley TBI but would like to try one off a Big Block that I also have. How do you get around the difference in the TPS and IAC plugs? Does anyone make/sell a jumper wire/plug? Kevin