Swapping in a 95 TBI 454, adios 91 TBI 350

[Hopper]

Hello everyone,

New to site, new post, hoping for some help.

I been beating up the google search bar and kept liking what I have found on this site. You guys have lots of good info. I believe I have all aspects of my swap figured out other then the best route for my computer. I'm swapping out my worn and high mileage 91 TBI 350/4l80e for a 95 TBI 454/4l80e. The engine comes complete top to bottom minus the wiring harness and the computer due to the fact the truck had a cab fire and those items where trash. I hope to use my factory harness and....

Is my best option to have a chip made/burned and put it into my computer? (Is that a dumb question?) or should I look for a 454/4l80e factory computer and just run that as is? or get the right computer and still have a PROM burned? Is there a computer code I can use in reference when looking for the correct computer?

These might be very simple things that I can still search and find but I've been sifting through so much I need a break. I know some of you know this info like the back of you hand. Thanks for any help given.

[myburb]

My opinion would be to switch to computer that came with that setup. Would probably have been 7427 running $OE or $31. If you can't find a harness you could probably modify your original. I think on the net there is articles on repinning.

[dave w]

I like the option of re-pinning the 91 TBI computer connectors so you can use a 95 454 computer. Here is a link to how I did the conversion: http://www.gearhead-efi.com/Fuel-Injection/showthread.php?173-1227747-to-16197427-Conversion-PCM-Swap-with-Wiring-Pinout-Directions!

Basically re-pinning allow you to use the 95 454 computer with the 91 harness. A few from the original 91 harness might need to be lengthen?

The 95 454 throttle body might need a 700R4 TV cable bracket modification?

dave w

[Neukam]

Repining to the later pcm is probably your best option using a 16197427 or 16196395. If you're going to use the transmission from the donor, you may have to change the connector for the transmission as well. I'm not an expert on the subject, but there were changes to the 4l80e over the years. The PCM doesn't need to be specific to a 454, but the memcal does. The memcal contains the code to run the engine and transmission as well as the knock filter circuitry and limp home mode circuitry. A new chip can be burned to replace the one on the memcal to change the calibration, but it must be a v8 memcal, and I'm not sure if the 454 used the same knock circuit, so it would be best to start with a memcal that matches your setup.

Info about transmission differences: https://youtu.be/Bjap2Th8tIE

Info on $0E: http://www.gearhead-efi.com/Fuel-Injection/showthread.php?337-16196395-PCM-Information-OE

[dave w]

I watched the transmission video posted above. Awesome information on the mechanical differences of the 4L80E. :thumbsup:

I'm wondering what internal electrical / electronic differences there might from the early 4L80E 1991 - 92 vs. the 1993 - 95 ($OE & $31) electrical / electronics.

dave w

[Neukam]

A transmission guy would know better than me, but it is likely to be electrically the same internally. They probably had issues with the old style connectors leaking or breaking and redesigned it. Don't take my word for it, though. Do your own research. Maybe call Baumann Electronic Controls. They sell aftermarket transmission controllers for these transmissions and others. They would know if there's any differences in the electronics or control strategy.

[dfarr67]

Did these 454's run knock sensors? If not- why not?

[dave w]

Did these 454's run knock sensors? If not- why not?
Some early TBI 454, mostly 1987, did not use Knock Sensors.

The wiring schematics for the 1993 - 95 454 / 4l80E show Knock Sensor wiring. Note: 1993 - 95 TBI 454's have the Knock Sensor module inside the computer memcal, not mounted on the engine.

dave w

[Neukam]

I'm not sure. GM may have decided to just run a very conservative timing map and not use knock. On small blocks with knock sensor, I believe the PCM will advance the timing at WOT and listen for knock as a way to self test the knock sensor and related circuitry. Perhaps GM didn't want to run the self test routine on an engine in a heavy vehicle, in a high load application. Does your donor not have a knock sensor? On the small blocks they were on the right side of the block down low where the coolant drain would be. I don't know about the big blocks.

[Neukam]

Note: 1993 - 95 TBI 454's have the Knock Sensor module inside the computer memcal, not mounted on the engine.

In case you didn't know, Dave is referring to the knock filter/sensing circuitry being on the memcal as opposed to using an ESC module mounted to the engine, as used in earlier trucks (or near the ECM in earlier vans). The knock sensor itself would still be mounted to the engine.

[dfarr67]

Mine has an upgraded ESC module (carb application) now mounted on on the firewall due to TPI but have head about 454 applications that did not. Seems strange that a HD application doesn't have the protection afforded to other models. Davew, any updates on your LS conversion thread?

[THEFERMANATOR]

For the trans, it goes 91-93, then 94+ as far as controls go. Yes the harness changed mid year 93, but the pcs and valve body did not change until 94. So use the correct programming for your trans as 91-93 requires a "cleaning cycle" every 10 seconds to keep the pcs clean and functioning. Every 10 seconds it goes max line pressure to stroke the pcs to clean it. There is an accumulator/buffer circuit built into 91-93 valve bodies to slow line pressure response so the cleaning cycle doesn't damage anything.

Also of note, all v-6's, small block's, and big block's to 93 ran low pressure injection(8-13 psi), but 94/95 454's ran high pressure tbi(32-38 psi) injection, and the stock injectors in a 95 are actually some of the smallest used, but compensated with higher fuel pressure. So make sure which injectors you're using and use the correct fuel pump capable of supplying the needed pressure(most run the 96/97 vortec pump for overkill, or a tpi pump). Tbi pumps are lucky to hold 13 psi from my experience, 94/95 454's had a different pump(40 psi), tpi's another(50 psi), and 96/97 vortec's used the highest pressure pump(65 psi). Running the wrong combo can lead to some NASTY hiccup's and extreme lean out.

[Fast355]

For the trans, it goes 91-93, then 94+ as far as controls go. Yes the harness changed mid year 93, but the pcs and valve body did not change until 94. So use the correct programming for your trans as 91-93 requires a "cleaning cycle" every 10 seconds to keep the pcs clean and functioning. Every 10 seconds it goes max line pressure to stroke the pcs to clean it. There is an accumulator/buffer circuit built into 91-93 valve bodies to slow line pressure response so the cleaning cycle doesn't damage anything.

Also of note, all v-6's, small block's, and big block's to 93 ran low pressure injection(8-13 psi), but 94/95 454's ran high pressure tbi(32-38 psi) injection, and the stock injectors in a 95 are actually some of the smallest used, but compensated with higher fuel pressure. So make sure which injectors you're using and use the correct fuel pump capable of supplying the needed pressure(most run the 96/97 vortec pump for overkill, or a tpi pump). Tbi pumps are lucky to hold 13 psi from my experience, 94/95 454's had a different pump(40 psi), tpi's another(50 psi), and 96/97 vortec's used the highest pressure pump(65 psi). Running the wrong combo can lead to some NASTY hiccup's and extreme lean out.

Not all V6s or small block V8s used the low pressure system. The later model vans and some trucks with the speed governed TBI units built like the 2 ton truck 366/427 TBI units also had high pressure fuel systems.

[Hopper]

So locally at a salvage yard, I have found a 94 2wd 454 4l80 in their inventory that got dropped yesterday. I'm going to run and try to salvage the computer and harness before it get pillaged. The concept is this should do everything I need as they should be almost identical. The only difference is I am 4wd. The transfer case holds the speed sensor and the 4wd indicator light for the harness. As long as I extend the speed sensor wiring, all working functions should be normal. Am I missing anything? Does the 4wd indicator run through the ecu?

[THEFERMANATOR]

So locally at a salvage yard, I have found a 94 2wd 454 4l80 in their inventory that got dropped yesterday. I'm going to run and try to salvage the computer and harness before it get pillaged. The concept is this should do everything I need as they should be almost identical. The only difference is I am 4wd. The transfer case holds the speed sensor and the 4wd indicator light for the harness. As long as I extend the speed sensor wiring, all working functions should be normal. Am I missing anything? Does the 4wd indicator run through the ecu?

On 94+ the 4 low input is connected to the ECM so it knows when it is in 4 low to modify the speed sensor reading by the low range ratio. Not sure if the 2x4 BIN file will have the 4 low tables in it or not, so you may have to find a 4x4 BIN file to use. You will have to modify your trans some to work with a 94/95 control system as there is no way to add in the cleaning cycle for the PCS into the 94/95 code that I've ever heard of. But it's not hard to change the force motor and internal harness to make it work.

[THEFERMANATOR]

Not all V6s or small block V8s used the low pressure system. The later model vans and some trucks with the speed governed TBI units built like the 2 ton truck 366/427 TBI units also had high pressure fuel systems.

I was speaking of pickup's, but everything I had found said that all vans also stayed with the low pressure system, even the rare 96 TBI vortec. I know that non road going TBI switched to high pressure injection in 94. Used to work on boats and some of those ran as high as 60 PSI on the TBI set-ups.

[Fast355]

I was speaking of pickup's, but everything I had found said that all vans also stayed with the low pressure system, even the rare 96 TBI vortec. I know that non road going TBI switched to high pressure injection in 94. Used to work on boats and some of those ran as high as 60 PSI on the TBI set-ups.
Nope I have played with some that had the 30 psi system. Used the weird TBI with the governor on the side.

[Fast355]

1995 G30 cutaway van school bus engine.

[Hopper]

Well, this has been both fun and educational. Joking, not so fun unless fun stands for frustrating. ��

I went the route of the 454 with factory wiring harness and computer from the donor motor. I have spent lots of time chasing wire and checking diagrams. Suburban runs and drives around the lot but here are the issue I have yet to find the end to.

Will not come down off high idle. 4 wire iac and the diagrams show all its wires straight from the computer.

Back fires and wont gain rpm unless the throttle is slow and smooth. I feel once these are fix I may have other things to work through as well.

Any advice on thing I should be looking into?

[stew86MCSS396]

For the trans, it goes 91-93, then 94+ as far as controls go. Yes the harness changed mid year 93, but the pcs and valve body did not change until 94. So use the correct programming for your trans as 91-93 requires a "cleaning cycle" every 10 seconds to keep the pcs clean and functioning. Every 10 seconds it goes max line pressure to stroke the pcs to clean it. There is an accumulator/buffer circuit built into 91-93 valve bodies to slow line pressure response so the cleaning cycle doesn't damage anything.

Also of note, all v-6's, small block's, and big block's to 93 ran low pressure injection(8-13 psi), but 94/95 454's ran high pressure tbi(32-38 psi) injection, and the stock injectors in a 95 are actually some of the smallest used, but compensated with higher fuel pressure. So make sure which injectors you're using and use the correct fuel pump capable of supplying the needed pressure(most run the 96/97 vortec pump for overkill, or a tpi pump). Tbi pumps are lucky to hold 13 psi from my experience, 94/95 454's had a different pump(40 psi), tpi's another(50 psi), and 96/97 vortec's used the highest pressure pump(65 psi). Running the wrong combo can lead to some NASTY hiccup's and extreme lean out.

@Hopper If any of the above statements regarding fuel pressure is true, I'd be questioning if you are running the correct fuel pump. I will say with 100% certainty that your '91 350 uses the lower 8-13 psi fuel pump. You need to determine which injectors you have in your 454 TB and run the correct fuel pump accordingly.

[Hopper]

I think the iac was stuck. After removing it and shoving my finger in the iac hole in the tbi unit. It came down off high idel but now is running super rich. I don't think the vacuum advance disconnect wire is working for timing it also. The timing isn't changing between connected vs unconnected.

[Hopper]

So I think I'll be taking it to a shop this week unless I can figure out the malfunction. Swapped the 92 ecm with the 91 ecm and right on start up the rpm's dropped down to around 700. Seemed to run super clean for about 10-15 seconds before developing an issue. Obviously, I still have a sensor issue as it make the engine run rough. but runs way better with the SBC ecm. Under closer inspection, the 92 ecm is a ac delco remanufactured replacement. Not sure why and it has a hypertech chip in it. This I knew. This was a running truck that I drove to the shop before removing the drivetrain for the swap. It seemed to have a miss but I chocked that up to the rig sitting for years. bad gas, bad clogged injectors, just a tune up in general. It still ran good with good power. any thoughts? thanks.

[stew86MCSS396]

@Hopper If any of the above statements regarding fuel pressure is true, I'd be questioning if you are running the correct fuel pump. I will say with 100% certainty that your '91 350 uses the lower 8-13 psi fuel pump. You need to determine which injectors you have in your 454 TB and run the correct fuel pump accordingly.
Have we established that you’re running the correct fuel pump? Here’s an interesting read regarding the IAC…

http://www.gearhead-efi.com/Fuel-Injection/showthread.php?4888-5-7-to-7-4-tbi-swap

[Fast355]

@Hopper If any of the above statements regarding fuel pressure is true, I'd be questioning if you are running the correct fuel pump. I will say with 100% certainty that your '91 350 uses the lower 8-13 psi fuel pump. You need to determine which injectors you have in your 454 TB and run the correct fuel pump accordingly.

If everything is straight off a 95 he does have the wrong fuel pump if it is still using the 91 fuel pump. At the most the 91 fuel pump will run 15 spi. The injectors used in the high pressure 454s have the same flow rate as a LB4 4.3 V6 when run at low pressure. Obviously not enough to feed the 454. Luckily a 96 Vortec pump will bolt right onto the TBI sending unit.

[Hopper]

I have replaced the fuel pump with the mentioned vortec one. i haven't check fuel pressure but i assume with the replacement and the new fuel filter I installed. Lack of fuel isn't the problem unless the computer is having the injector spray enough. They do have a nice even flow with even spray. As I have mentioned in another post. I have no CEL. I don't know if there is a wiring issue which could be but I wonder about the computer as well. The whole computer is a factory replacement according to the sticker on it. the issues I can get passed right now is the trans is in limp mode and the aldl isn't working either. I borrowed a scan tool and it can't connect. i feel this is part of my CEl issue.

[THEFERMANATOR]

Have you made sure your ALDL plug is wired correctly? I know early trucks ran the serial data to pin E where the later PCM's ran it to pin M. I ran into this on the 7427 swap I just did where I couldn't communicate with it. Swapped the wire from E to M and it worked perfectly.