oldred95

I'm kind of in a pinch here and I've already emailed dimented24x7 and fast355 is aware of what going on but I haven't heard from either of them and I'm in search in info. Basically I've converted to MAF and everything is done and correct except for the tuning aspect. For some reason it starts and dies. Watching the injectors and listening to them they fire like a machine gun and then drop off real fast and then stop spraying all together, this is all within a second or so. Something it telling it to shut the fuel off to the engine. I have a brief log of it doing this too. And I am using the MAF code from dimented and I double checked all my wiring and pin locations and that is all good. The MAF's condition is unknown but appears to be working and it starts and dies with and without the MAF plugged in. Without it plugged in should be defaulted to speed density. I have yet to try an old speed density BIN of mine to see if it will run on that but I'm thinking it will. Apparently I failed to get something set right in the MAF bin and it doing strange things. You can see as the MAF signal falls the vehicle MPH rises on the datalog. The PCM is seeing the MAF signal as a vehicle speed input. Also the injector PW starts out at 30.40 with the key in run engine off and drops like a stone as soon as it starts. I know whatever is wrong is in the BIN but I'm too green to know exactly what isn't right. Can anyone give me some insite to this or what it might be? And that is a playback of the MAF in operation, I just had the speed density BIN open to burn it to so I can try that tomorrow just to see if it will run on it.

Grim Reaper

IAC position is too high (150). It is hard to determine if this is a "symptom or a cause". Maybe it is trying to enter the "Idle Routine" but won't idle due to something missing.

Have you re-adjusted you IAC (as a starting point).

dimented24x7

iTrader: (2)

Sorry, didnt have a chance to check my mail over the weekend. As far as the MAF goes, it takes a couple hundred milliseconds after startup for the computer to set a code and switch to SD with the MAF unplugged. The first cell in the MAF table can be adjusted to provide extra fueling if needed when no MAF signal is present for startup, but that can be fixed later. The MPH thing may just be the ADS file. I think the MPH term may not have been updated to the correct address. Ill look into this and get back...

oldred95

I wondered about the IAC. I guess its worth mentioning that I also threw on a 454 TBI unit in the procress and made an adapter harness so I could easily switch back to the stock TBI and my IAC connectors would all be there. Well I went by the book and I'm sure I've got the IAC harness wired right but the IAC came with the TBI so its hard to say if its good or not but the IAC counts did move a little at one point. I'm using the IAC settings fast355 told me to use that he is using with his marine 2 inch TBI unit. Also I have my IAC park counts set at 255 if that matters. I liked the little spike in rpms it gave the engine at startup with the old TBI. I'll try and plug the IAC port tomorrow and see what it does as far as idling. When it starts it sounds like a MASSIVE air leak, similar to when the IAC opens all the way up like when you crank a rocker down and the engine stumbles and the IAC opens way up to keep it going.

dimented24x7

iTrader: (2)

As for the MPH, ignore it. I have a custom ALDL transmit table set up in my latest bin for my car that uses the trans. output speed as the MPH. Currently its reading the distributor reference period. The bin with the correct transmit table on my laptop, so when I go get it, Ill get the bin so you can snag it.

The IAC counts look ok. I think the computer is trying desperatly to stave off a stall. How big are your injectors? Not a bad idea to double check that before continuing on. Currently, the default values in the injector flow vs. vacuum table are set up for injectors that flow 10.2 grams per second. If you have smaller ones, itll be lean, and want to stall. To compound this problem, the stock calibration is set up to run lean. The open loop AFR at 30 degrees C is 16:1! If the injector constant is too large, the MAF table is off, and the computer wants to run at 16:1 when your off idle, it can cause some major problems. I recall having start/stalls when I first hooked up the MAF as well. It would start, stutter for a second or two, and crap out because the stock MAF tables where off. The only way to keep it going the first time I ran it was to pump the TPS sensor to make the computer think it needs TPS AE. GM makes a whole crapload of different MAFs with different calibrations. You may just need to recalibrate the table. Also check and make sure that the MAF wires are clean. They should be a shiny silver color. If theyre black and covered with crap, the sensor will underreport the airflow. You can buy a can of CRC mass airflow sensor cleaner at most autoparts stores to clean off the wires.

Also, careful with those option bytes. Yours appear to still be defined for the stock $0D code. The MAF ones are MUCH different as I customized alot of the code. See my MAF source code for more info on these. Also make sure that the option to use a manifold temperature sensor is UNchecked. This option is for cars with unheated manifolds that need additional compensation for the acceleration enrichment. You DONT want this to be checked off when your using a 4L60-E as the manifold temperature sensor and transmission fluid temperatur sensors share the same output, and the option bit tells the PCM which is in use, and what routines to skip or run.

oldred95

My injectors are now 46# running at 35 psi so a flow rate of 10.00 going by what the spread sheet I have says it should be.

The bytes you speak of are in the ALDL scan tool xmission address table correct? If so I show them to be correct with the MAF code you sent me because all I did was copy all my settings over from the old speed density BIN's to the new MAF code bin and burned it onto a chip. I just unchecked the MAT inuse Flag too.

dimented24x7

iTrader: (2)

Thats WAY too much park position, especially with the larger IAC those 454 units have. You want to have some of the air going through the TBI rather then around the TBI and all through the IAC or you'll have terrible fueling as the fuel will just puddle in the TBI or on the manifold floor, causing a lean cranking and sudden rich spike on startup. Having more of the air going through the TBI helps shear the fuel and atomize it. Also not allowing enough air to pass through the TBI bores prevents the PCM from priming the dry manifold when you first start cranking, resulting in longer startups and a start/flare/dip condition once it catches.
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Also, what address did you change when you changed the IAC park position? Because from the datalog, the park position is still set at 150 counts.

oldred95

LOL well it appears I don't have the IAC counts set to anything but stock afterall. I guess I never realized I didn't have an address for the IAC counts constant so I was just changing numbers but it wasn't really changing anything. Well this makes me look like an idiot. I guess I need the address for the IAC park counts. I'd look it up but I have a terrible time trying to understand the Hack or source code, whichever you want to call it.

Nevermind I found the IAC park address. This is it correct? L4EA6

dimented24x7

iTrader: (2)

Yes. For now, though, Id let it be while you get the fueling sorted out. If anything, you may want to reduce it. Also keep in mind that the IAC park position isnt the only thing acting on the IAC counts during cranking. If the engine temp is warm enough, the PCM will also move the IAC as soon as the PCM has power.
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Its a lot of info squeezed into one document. Theres so much there that even I cant remember it all. If you post up the parts you dont understand, Ill walk you through it so your not so overwhelmed.

RFmaster

I have a 'dumb' observation - why is fuel pump voltage reading 0.0 Units? Perhaps because of custom ALDL mapping?

//RF

dimented24x7

iTrader: (2)

Good observation, actually.

Double checked, and it is because he doesnt have the updated ALDL xmit table.

Grim Reaper

I assumed this is a "snap shot" taken just prior to startup as there is 0 seconds of running time. Typcially the voltage of the fuel pump on a running engine is the same (within .1 volts) as the battery. But just prior to "start up" it will be zero because the fuel rails are all pressurized and the fuel pump is not running. But once the engine starts, it should be the same voltage as the battery.

But, it does raise an interesting question as only oldred95 knows exactly at what point these scan results were taken. I also notice the O2 sensor has 0 mV.

Note: I posted just prior to dimented's post.

dimented24x7

iTrader: (2)

The first snap shot appears to be with the engine running as the MAF frequency is non-zero and the engine is at 1925 RPM. The O2 is 0 because of the xmit table he has. The table in the source code is there for testing the software on the bench or in the car. A sizable block of addresses is reserved for monitoring the software and hardware when testing, and returns 0 when datalogged.

From the snippet of the datalog, the MAF is working. As far as the injector PW goes, it will start out very high while cranking and get much lower as the engine speed builds. From the first datalog snapshot, the injector PW is correct for the given MAF flow and engine speed. I personally think its just lean. Scale the entire MAF table up by 15% and see what happens. For my MAF that I have, 3750 Hz is over 20 gms/second of airflow, so the calibrations do vary from MAF to MAF, depending on what year and model you got it from.

oldred95

Was still getting a MASSIVE vacuum leak sound even with the IAC closed and unplugged so I pulled the TBI back off and sure enough the gasket fits the adapter just fine. Flipped the TBI over and held the gasket to it and found that there was a good 1/2 inch gap at the rear of the TBI that wasn't being sealed. So I cut a new gasket for it and set it on the adapter and then noticed the adapter isn't machined right for a 454 TBI, yet that is what the adapter is made for and came off of, an early model 454 TBI. The sealing surface at the rear of the TBI isn't wide enough on the adapter. So I put my stock TBI back on and it starts and idles fine but that was with an older speed density BIN as well. It did some funky things to the transmission running a speed density chip with it wired for MAF but I got it back to the house and out of my dads way. I never even tried the MAF again but I think it is going to work now that I've got the vacuum leak fixed. I won't be back home for another couple weeks so I won't really know much more until then.

dimented24x7

iTrader: (2)

That will do it. Large vacuum leaks and MAF dont go together well.

As for it acting funky, if you forgot to check off the option to use the magnetic VSS in the old SD chip, then the computer would have been using the MAF signal as its TOS reference! Any time you want to use an older SD bin, b4 of option byte L5D02 must be set to 1. This will tell the computer to use the magnetic VSS TOS input thats tied to pins F4 and F5.

oldred95

I figured thats what was messing with the shifting but with my old man breathing down my neck I didn't have time to change the bytes and I just stuck a chip in it with a previous BIN for speed density. I think I've figured out the cause of the vacuum leak too. I am using a spread bore to TBI adapter plate from an 87-91 454 TBI truck and the 454 TBI I've got is for a 92-95 454 TBI truck. You'd think they would be the same but they aren't. The TBI I've got has two passages running along the back side of the bores and they extend past the sealing surface on the adapter plate and therefor causing a big vacuum leak. So I'm stuck with the old 1 11/16 bore TBI for a little while longer. But after I get enough ducting and what not I should get the MAF and filter setup done and I think it will be drivable. Thanks for your help guys. I guess I should be a little more observant but I learned something from it so I guess it all works out.

dimented24x7

iTrader: (2)

Heres the table for the ALDL.

dimented24x7

iTrader: (2)

Also, make sure you import the correct ratio for calculating the MPH from TOS RPMs from your stock bin. If this is off, youll have early or late shift points at part throttle. The constant is all the way at the end of the Constants/Scalars in tunerpro.

oldred95

I got the byte table corrected in my BIN. I should probably do the same to the original copy of the MAF code as well.


As for the ratio you are talking about the rpm vs vss ratio correct? As far as I know it is 40 rpm, or ppm, whichever it is. If so they yes I corrected that.


Also I was able to pick up the entire vortec 350 truck air cleaner system from the fenderwell to the throttle body minus the MAF sensor (it was in bad shape) for 15 bucks today. Should be enough to get the whole riggin up and running on my next trip home.

I also decided to go ahead and modify my adapter plate by building the flange up with JB weld and blocking it down so I can use the 454 TBI.