Help with fresh start up. Olds 455 MPFI $0D

[BigBanks78]

Can anyone help me adjust the crank, start and run, iac and idle settings? What do you guys do when starting from zero? The below paragraph is just issues I'm having and can be disregarded if it's to long, I guess I really just need a step by step of what to do to get things close enough to start driving to tune it. Maybe a link to a .bin that has the pe hack and all the cool mods installed?
I have my Regal running but its using so much fuel its unreal. Just starting and trying to get the Idle off 10afr has used 1/2 a tank In several start ups. I'm just wondering if I took to much off the idle ve and the computer is compensating. its in open loop so I didn't think it would But I have gone back and forth with the injector settings and ve settings trying to get it from not starting because not enough fuel at start up to straight 10's on the meter. I have 48# accel ls style injectors and a 400lph (or close) boche fuel pump so I wouldn't have to upgrade later if need be. Fuel pressure is at 43#'s or close. It idles at 1200 rpm 10afr but goes to 19 afr if I hit the throttle. Ive moved the ae settings and always get the cough at first touch of the throttle. I started with a .bin my dad is running his olds 403 mpfi with but I have a ls throttle body, he has a 4 barrel carb type TB. I took the iac motor out and plugged the hole and the iac is all the way up and when i hit the throttle it pushes the valve in. I am in the opinion that the iac is doing the opposite of what it should b doing, so I checked the wiring and is correct. Would making a log and running through the spreadsheet help with these issues? My dad did not tune his the way I have read you are supposed to, he made the afr meter read what he wanted from the ve and didnt use pe at all. Throttle blade is closed all the way and dies if i plug the iac inlet hole.
Thanks for the help

[dave w]

The attached show how to set the TBI IAC.

Possibly the below procedure will verify the IAC is working correctly / wired correctly by verifying the IAC pintle is fully extended. Seems likely the IAC will need to be removed to verify the pintle position.
1- Engine warmed up, key OFF, tranny in PARK
2- Put a jumper wire from pin “A” to pin “B” on the ALDL
connector (should be the black wire & white wire) A metal
paper clip works good for this.
3- Turn key to ON, do not start engine, wait 10 seconds. This
will extend the IAC pintle and close off the air passage in the
body of the TBI. Remove the electrical connection to the IAC
by pulling it straight out. Turn the key to OFF and remove the
jumper from the ALDL connector.

[BigBanks78]

That's great, very helpful to know what the counts and tps voltage should be! This helps with my truck as well. Thank you I will update after i try this. Not knowing the target data or correct readings is my main issue... Again thank you very much!!

[1project2many]

Can anyone help me adjust the crank, start and run, iac and idle settings? What do you guys do when starting from zero?

We can try. cranking and startup can be tough. Luckily idle and running settings are usually a little easier.

That's great, very helpful to know what the counts and tps voltage should be!

TPS should be below .72V. IAC counts stock are usually around 25-32 but in the beginning of tuning this isn't as important. And the more modified your engine is, the more likely you won't see stock IAC numbers.

I have 48# accel ls style injectors and a 400lph (or close) boche fuel pump so I wouldn't have to upgrade later if need be. Fuel pressure is at 43#'s or close.

Did you change the injector constant to match the injector? Did you change the injector corrections as well? These can make a big difference in fuel delivery. Some people spend years chasing their tails b/c they don't get these right in the beginning. I usually set the injector values then leave them alone.

I took the iac motor out and plugged the hole and the iac is all the way up and when i hit the throttle it pushes the valve in. I am in the opinion that the iac is doing the opposite of what it should b doing, so I checked the wiring and is correct.

That definitely seems backward. Are you able to see IAC direction or IAC counts in the scan data to confirm which way the ECM is commanding the IAC to move? Dave's method to check IAC operation is pretty easy. If the IAC really is operating backward you need to swap two wires in the IAC connector. It doesn't matter which two, just swap two. I usually swap the blue and blue/white or blue/black. Some IAC motors are wired differently internally and require this change.

I'm just wondering if I took to much off the idle ve and the computer is compensating. its in open loop so I didn't think it would

The computer does not compensate for AFR issues in open loop so no need to worry about somehow adding issues to the tuning process.

Would making a log and running through the spreadsheet help with these issues?

It sounds like you have some more troubleshooting to do, but it can be very helpful to take time to write down changes and settings. First, it gives you time to sit and think. Second, you can end up changing so many things that you forget what you've done.


As far as the actual tuning, Cranking can be very challenging. With a "completely from scratch" build I like to have a fuel pressure gauge available to put on the system during cranking, at least in the beginning. Why? I once spent an entire day trying to make a car start by adjusting everything I could think of in the ecm when it turned out the way the fuel pump was wired, it wasn't getting enough power during cranking.

Are you using a wide band O2 or just the stock style O2 sensor? Is the sensor heated? Is it getting warm enough to read accurately? Either can work, but I like using O2 voltage for a NB sensor instead of AFR. NB sensors are not accurate for AFR outside of stoich.

Timing is a really big player in cranking. What is your timing set to? Setting the distributor more advance during cranking is ok, just be careful not to go too much. I've worked on engines that liked 10 degrees base timing. If that's what works best, I'm ok with using it.

I like to get the VE and timing good at idle and off idle then work on cranking after the fact. It's ok to use a little starting fluid or a starting aid to get the engine to light off, just keep safety a priority.

Do you have something like "desktop dyno?" I've used that to create a starting VE table before. The shape of your VE curve will end up close to the shape of your torque curve. DD doesn't generate a torque curve at low rpm but if you start with 0 VE at 0 RPM you can fill in th emissing numbers to create a rough calibration.

[BigBanks78]

Ok I have the injector constants set for 48# now, I was moving the # down to move the whole fueling around trying to get the maps in the middle. I read to play with them to find a good % like if the ve is to close to the top move the # down. I got the offset from the website and set them but only got the offset for running voltage so i sloped up for less voltage and down for more. I do not know about "injector corrections". I am about to start warming the car up now to reset the iac. I wasn't looking at the data stream while doing the start up and started thinking like u send and wondered if I closed the throttle plate so far that the tps doesn't read until its opened and yes i can push the pedal down what i'm guessing is 2-3-% before the tps registers as moving in the data stream so hopefully doing the iac reset and making the tps adjustable that will fix the cough. I have an AEM wideband on it and a fuel pressure gauge in the fuel rail, I still have to make an extension for the 1 wire O2 for the long tube headers O2 bung location. I did turn the distributor at first to the best place to get it to start and left it until I can get it idling correctly to set initial timing. I will try the Desk top Dyno. Thanks for the info I'm going to check the iac now, I will update :)

[BigBanks78]

Hey dave I didn't read in that pdf if I needed to disconnect the ignition bypass wire to do the iac reset. I tried it on my truck last night and couldnt get a stable idle because the timing was fluctuating.

[BigBanks78]

Ok made progress. The iac isn't long enough to reach the bottom of the air port so I made a spacer on the lathe. After resetting the iac and setting the throttle blade I had to cut out a bunch of the tps to twist it enough to register then add 15% or so to the Idle ve to get it into the 14's. I guess revving 12-1500 at idle kept it in open throttle ve or who knows y it was a flat 10 afr. I green lock tighted the spacer in but I guess it didn't dry because it came up the bore a bit and got stuck passing a bunch of air through. Its hot and I drove it back down with more green stuff and am going to let it sit over night to see if it sticks, may brad it in... and the fuel pump does stop while cranking so I gotta see why thats happening. I'm getting knock data in the data stream at idle and O2 sensor data as well, the O2 sensor isn't plugged in.I have noisy aluminum roller rocker arms so wondering if thats it or electrical. More bugs. BUT oh boy it sounds GOOD! :)

[dave w]

Something seems odd to me, why would a LS IAC not bottom out on a LS Throttle Body.

Does the LS throttle body have a LS IAC.

I've seen "swap meet" LS Throttle Bodies that knowingly had or not knowingly had incorrect IAC parts.

[BigBanks78]

I wasn't sure if It mattered so I took an iac from a tb I have in my salvage shed. I have 4 I was comparing and all had different shaped heads. I can try and find an LS style this weekend. Its an ebay TB.

I wasnt getting the idle low enough after the first iac reset so tried it a couple times and wasn't getting the iac to stay out so I switched the 2 HI wires and got the idle to 850-900 then turned distributor back till it idled about 750 then it wouldn't start without carb cleaner to help. I'm not seeing the iac move much so I'm going to change the iac before I go any farther and try to figure out if maybe my rocker arms are to loose making the knock sensor sing. But it drives and the idle isn't bad or pushing through the brakes. Ive driven it back and forth to work the last couple days working to get the ve in the general area. drove it to get lunch yesterday and gassed it a bit, it threw me back in the seat so am definitely excited :)

Any way on the 2 HI iac wires, did I switch the wrong wires? The first 2 wires you specified were a HI and a LOW on the diagram. Also I unchecked the "Crank Fuel All Injectors Each DRP", I didn't see if it ran all injectors while checked or unchecked. seemed like it blew more black smoke for longer after start after I unchecked it so guessing I turned on "all injectors". I'll get some of this stuff straight in the mean time. Thank you!

[1project2many]

Sounds like progress. Any two wires can be switched so that's one you can't get wrong. Does the ECM think the transmission's in drive all the time? That will add some timing and can make RPM a little higher. Same if it thinks A/C is on. Knock sensor isn't used during cranking so shouldn't be part of startup issues. Maybe the distributor needs to be advanced but the "reference angle" or "base timing" value needs to be adjusted to match so it will start easier and idle correctly?

[BigBanks78]

I haven't had time to look for another iac but I'm thinking it's not acting correctly. It only moves when I hit the throttle, stays at zero steps no matter how low the idle is particularly after cold start when it idles so low it barely stays running. I'm gonna try hooking up an iac externally an see how it moves. It still won't start without spraying carb cleaner in a vac tube. Turned the "Crank Fuel All Injectors Each DRP" off and back on. Adjusted the "Crank BPW vs Temp" down a little and up a little a couple times, not seeing a change. I may up the timing at 400rpm again, that seemed to help but still not starting on its own. It did start on its own more times than not when i first started but it would kick back like the timing was to advanced. After it warms up it runs fine and it will start unless I leave it sit for a while then it takes a bit. Also I have things hooked up correctly as far as I can tell but the fuel pump stops when I hit the starter and sometimes doesn't kick back on after I let off the starter, Ecm is controlling the pump relay. I will set the initial timing here soon, i have twisted the distributor back and forth a bunch missing with starting so probably need to start over based on where its sitting now. Oh and I found out that if u curl the knock sensor into a circle trying to take up a bit of slack it creates an electrical feed back signal and the ecm sees it as knock...