Fredless

After finally finding the pigtail for the IAC, buying a dremel tool I finally did this swap. Also grinding off the linkage from my spare SBC TBI and grinding off the 454 Linkage, and having the SBC linkage tack welded on the 454 throttle shaft.

Took me about 4 hours, which includes boring the manifold and ultimate TBI'ing the 454 TBI.

I matched up perfectly the wires, and triple checked the A.B.C.D. wires and crimped them in. I also did the IAC reset procedure thing and waited 30-45 seconds till it stopped making its little noise. Cleaned it also, really well. Also cleaned up the TPS. Just a little info, this was bought on ebay and was a junkyard 454 TBI.

Anyway, I cranked it up a few minutes ago at 11pm and it started idling high and seemed like it was going higher in a span of 5-10 seconds so I cut it off quick. Did the IAC reset, and cranked it up WITHOUT the IAC hooked up and it still idled extremely high and seemed like it was going higher, so I cut it off again. Keep in mind the TPS was hooked up.

Any ideas what is going on? I made sure the shaft wasn't sticking high, it shuts all the way closed (well the way Rochester set it). Could the TPS be causing this? I really don't know what that damn thing does. Does the TPS control Idle in anyway?

If the TPS is a possibility in causing this problem, please post and I will put my SBC TPS on the 454 because they are the same thing.

IROCaholic

What injectors does it have? I think the 454 tb came with 85 lb injectors , that is to much for your setup, also have you checked the gasket between the throttle body and manifold for leeks?How high are we talkin here like 2500 or higher or around like 1500. My car jumps to like 1500 when I start it cold and after it warms sits at like 850.So if its not incredibly high try letting it warm up for like 5 min. I really dont know much about the tps and IAC stuff though so I hope someone else can help you there. Good luck.

Fredless

I put my 65pph cop injectors in there, I knew the 454 injectors would be way to much without a chip.

Gasket - I had a new one in my rebuild kit, but I used the dremel tool and rounded the holes out to match the TB.

I don't know if thats causing it or not? Its a pain in the butt to find parts for the damn 454 TBI! Every idiot behind the parts counter is like whoa whoa what car are you putting it in, i'm like a 92 camaro BUT I DO NOT HAVE THE SBC TBI! Then they say "ohh well this is the part you need and of course they give me a part for the stock camaro.

I have NO clue what year this TBI came out of, obviously 90 up because it has the round TPS like my Camaro. So I tell them 92 C3500 1 ton truck and they CAN NOT FIND **** for it.. It pisses me off.

IROCaholic

I dont know what year truck came with the 454 tbi either, that sucks, But what rpms is it idleing at , like I said if its not to high i would try and let it warm up some, also just to be safe try using some sealant to seal the gasket to the thottle body and manifold , mine busted a while back and the damn thing was idleing at like 1900 rpms. Good luck.

lykan

Hold a sec, there is a thread here a guy had the same exact problem, found out it was in the wiring even tho it looked ok, a voltage check found out it wasn't read this post, let me find it...Here it is! this should answer all your questions


454 TBI swap blues is here!

Fredless

I used my holley neck down gasket and slowly and extremely carefully shaved it out to 2 inches. Still did the same thing.

I've read that post since I started this project and tried three different wiring methods for the IAC

The marked way (stock hookup)
A=Blu/wht
B=Blu/blk
C=Grn/wht
D=Grn/blk

Idled extremely high around 1900-2000rpm

The way the guy did on that post (sniperdsl)
A=Blu/blk
B=Grn/wht
C=Blu/wht
D=Grn/blk

Car wouldn't even stay turned over, even with IAC disconnected, shuttered and died. The IAC also did not function when I did the reset procedure

Here is how I have it hooked up now:
A=Blu/blk
B=Grn/wht
C=Grn/blk
D=Blu/wht

Same exact problem as the first time. I also switched the TPS's out and still idling.

I let it idle at 2000rpm for about 3 minutes, did not even slow down a tad

What the hell?

TechSmurf

You need to look at the diagrams posted on '454TB Swap Blues' a little closer.. The way Sniper_dsl ACTUALLY did it was:

A: Blue/White
B: Blue/Black
C: Green/Black
D: Green/White

OR - simply take the "marked" way as you posted it, and swap the green wires around. Done.

Fredless

Ok throughout all the posts in there it was hard to find out which way he did it. I did not try it that way yet. I'll try it tomorrow.

My question though, why does the car idle high right off the bat with the IAC hooked up and disconnected? It seems like having the IAC hooked up doesn't do a damn thing.

Pablo

iTrader: (1)

bottom out the iac by shorting the a and b pins of the aldl, when you look down and see the iac all the way extended disconnect it. Then try starting it.

It should idle low and if its cold may require you go give it some throttle to stay idling. If not you have a vacuum leak, it sounds to me like you have a vacuum leak from what youve described.

Fredless

Ok, I DID HAVE A BIG *** Vacuum leak. I noticed earlier today that the shute for the IAC to the driver's side bore HANGS OVER THE TBI plate on the GMPP Vortec TBI manifold! This manifold sucks even worse now! I hate it more!

To jimmy rig it, I dug my 454 TBI gasket out of the trash (which I thought wouldn't work, but I just put it on backwards damn..i'm dumb sometimes) and it fit but of course the gasket hung over the back. Started the car up, and it idled lower and if I pushed the gasket up, it would idle lower. So I thought ok, i'll fiddle with it. I did, and tightened the back bolts down first, really tight and it seated better, but not sealed. So, to jimmy rig it just so I could get to work today, I used RTV to seal it back there (I KNOW PLEASE DON'T YELL!) and let it dry for 2 hours. Did the IAC reset, procedure, enough minimum air. Plugged it back in and it idled PERFECTLY, better than it did with SBC TBI. It ran PIG *** rich with the 65pph injectors, so I scrambled to put the 305 injectors back on before work. Made me 20 minutes late but I did it.

So I'm ecstatic at this point, runs fine or so I think. I put in Reverse and it starts idling high again! 1250RPM idle while in gear if you do not apply any pressure to the pedal. Hell, thank *** I have the 2100 rpm stall converter so it doesn't slam into gear. I get to a stop light, still idling high. I throw it in neutral and the bastard surging idle comes back as it idles around 600rpm like it used to with the SBC TBI when I left it in drive at a stop light! I used to have to throw it in Neutral to raise the RPMS to get rid of that annoying *** surging idle. So now in gear it idled higher, neutral, idled lower!

So I go home tonight at 10 pm, its back to idling high as hell and stays that way. If i'm on a flat road, the car does not go below 1250 RPM or abouts and will cruise at 45mph, like having cruise control again! AND get this, if I press the brakes it will idle about 1400 rpm! What the hell?

Argh..Nightmare. I'm using Sniper_dsl's way of hooking up the IAC by the way. I'm going to switch it back to stock tomorrow and see how it goes. If this does not work, I'm going to see if my friend who helped me do my motor swap will trade me the 454 TBI for the Holley 670cfm back. He has the flat Holley 300-66 manifold that was mine. So he will not have any gasket hang-over problems like me.

Fredless

Ok solved all Vacuum leaks.

The problem is the bastard IAC sensor. All I can do is get it to work correctly one crank, BUT as soon as I put it in gear, the IAC retracts all the way and stays like that!

Also, whenever you step on the brake at lower speeds (around 45mph) the rpms actually go up 200rpm. Let of the brake, it goes back down to 1500.

My friend and I can only think its the 350 TBI chip from TBI chips.com going crazy. With the SBC TBI it did have a surging idle but at least it did not do this.

What do you guys think? Or another sensor possibility?

Fredless

Well Nevermind. My old 305 JET Stage 2 chip did not fix a darn thing.

Same old problem, reset IAC. Runs fine, then put it in gear and its screwed all over again. By the way, I bought this IAC from Autozone...Dunno if I should've spent the 90 bucks on the GM one.

Fredless

Ok since FL-Thirdgen and this site too can not solve this weird problem, and my dumbass can't either I'm throwing in the towel on the 454 TBI. I'm going to put my SBC TBI back on.

Thanks anyways guys!:hail:

lykan

are you sure your iac is still good? Youi hve had wires connected to it in quite a few different ways i figure...maybe it didn't like one combination?

Also a lot of wiring can be diffeenet colored even on the same year.. have you taken a volt meter to the wires to identify them positively instead of just going by color wire?

I wouold figure if you're at your wits end you might as well try a volt meter/ohm meter..if you know what the voltage to each of your 454TBI connections is, you can mark them.

Then take the volt meter, and test each one one your exsisting in car wires to identify them, and hook them up accordingly?

A lot of times wiring things up from scratch it would seem I had everything right(every possible comb it would seem.), and it just didnt work.. upon getting out the volt/ohm meter, the solution became obvious.

Am i making any sense? if nto I ll try to explain better i can be confusing... I know a 454 TBI will work on your car.. it's just a matter pof wiring it correct... I would hate to see you give up when you are so close.. sounds like a lot of work invested.

Fredless

Well one, where to I put the voltmeter on?

The naked wires or down the pigtails pins when its connected to the wiring harness?

Then when I get those readings, what do I do?

lykan

Well, if it is possible, find out what they are supposed to be.

Let's see how do I explain..
Perhaps find a running 454TBI(or a manual that explains voltages/resistance for each 454 connection) on a 454 motor find out what voltages and resistance is needed/standard for each connection.

Then take your 350 connectors, determine the volatge/resistance for each wire, match those to the 454 TBI?

I think this is how the last one was done. I'm no expert, but I am assuming if you match the correct output from each wire on the 350.. to the required input on the 454 TBI you should have it running correct.

I know the last swap had the same issues with the IAC, but they were solved.. it seemed none of he wires made sens as per schematic, but when hoked up it ran right.

67 ss

Do you have a scanner to be able to watch iac counts? First thing you need to find out is if the computer is commanding the iac mtor to open up causing that high idle. The way you describe it to me sounds like the computer is seeing to big a change in the map sensor when you drop it into gear and the computer thinks there is a load on the engine and opens the iac. Chevy trucks used to do this when they had bad torque convertors in the tranny.
Try this if you can get a hand held vacuum pump. Start the engine let it idle normal then unplug hose to map sensor put vacuum pump on it and pump to like 17 " of vacuum. Then put it into gear and see if problem is still there.

Good luck

va454ss

iTrader: (1)

Could the MAP sensor be bad?

Where is your MAP located?

Ideally, your MAP should be located higher than where fuel enters the TB.

Fuel vapors can ruin your MAP sensor.

Fredless

On the map sensor, I left it unhooked for some odd reason, I think it was one of those times I disconnected the fuel lines to remove the injector pod.

Anyway, the car ran without it hooked up! Noticed it was disconnected and hooked it back up and nothing. I remember a long time ago (still had the L03) I accidentially unhooked it while trying to find the hose the controlled the A/C vent selector and the car died, immidiately. I don't think it does that now.

My torque converter was installed in early August of this year...No way its bad.

Fredless

new MAP sensor only changed one thing, it now only idles high HALF the time.

Put it in gear, it idles high, put in park or neutral, it goes down....What the ****?

And how could gas vapor ruin it? Of course gas vapor gets into it, all the time. The vacuum port leads to some part on the butterflies and thats where the air/fuel is first mixed...Some gas vapor is bound to get in there.

va454ss

iTrader: (1)

Correct.


But, once the vapor condenses, fuel could settle in the MAP.

If it is above the point that fuel enters the TB, once it condenses, the liquid will run away from the MAP, not to it.

Fredless

Well any other ideas? New IAC and MAP sensor...Now what? And why the hell does it only idle high in gear and then once you throw it back into park or neutral, its fine?

It used to be once you throw it in gear, thats it buddy its idling high until you reset the IAC all over.

Pablo

iTrader: (1)

bottom out the iac and just unplug it, who needs the blasted thing anyways

might need to give a little gas pedal when starting it in the mornings

Fredless

LOL it will stall at lights then...F*ck this I'm buying the stock pigtail and going back to the SBC TBI. This has been a nightmare.

seanof30306

iTrader: (4)

1. i don't think ou should give up. plenty of people have done this swap and made it work. you're missing something.

2. there IS an easier way, however. send your small block tbi off to this guy http://users3.ev1.net/~thor10/tbodytest.htm

for 169.00, he'll send you one bored out to 2" with new throttle shaft bearings that will bolt up exactly like the stock one.

you can then turn around and sell your 454 tb. they go for 150-200 on ebay all the time, so you'll be essentially cost-neutral on the swap.

Fredless

Thanks Sean. I think I will do that. I already put my SBC TBI back on and I forgot how damn good the car ran before LOL.

I also scored my friends old 55pph injectors so it runs really good now. I was using the 40pph injectors that came with the 305 with my VAFPR.

Thanks for all your suggestions guys!

freaky

i'm in the exact same boat . just hooked up 454 tbi an it want to idle high . o steps showing on the ebl wud idle ats about 1800-2400 rpm 14 % dc voolts on the injecter