Question: 94 PCM to 91 ECU

[893508]

I'm purchasing a 94 LT1 6 Speed
I would like to install my L98 Holley stealth ram 520+ hp engine in this 94 c4..
My questions are.
(1) will a 90 - 91 TPI engine harness and ECU feed the ignition, interior, dash correctly without issues..
(2) or availability of after market harness kits to convert the LT1 harness to TPI
thank you in advance

 

[vetteoz]

My questions are. (1) will a 90 - 91 TPI engine harness and ECU feed the ignition, interior, dash correctly without issues..

Maybe.
Without comparing the wiring diagrams side by side there may be differences between the years in dash to engine bay connections not to mention the CCM is year specific

(2) or availability of after market harness kits to convert the LT1 harness to TPI

You could possibly run a standalone engine harness to suit the 91 '727 ECM and leave stock wiring to inside
LT1 has completely different electroniics on account of the Optispark
You know the stock HSR won't fit under C4 hood without mods?

 

[893508]

thank you for the response
Yes I'm aware of the LT1 optispark. I have a parts 93 z28 part car. I know fbody's convert to carb setups. there must be an adapter from optispark connector to HEI??
I have herd the HSR will not fit under the hood.of a C4. it would have to be the front section of the hood? I measured my TPI height before I upgraded to my HSR. the TPI is a 1/2 taller except the TB area where it angles downward.
I guess I will need to sell my hood for a ram air type..
do you know of anyone using a stand alone harness converting the C4 LT1
sorry to drag this out.. my engine is awesome.. and I want to make it's new home in a c4 I guess i will need to Pick out a 90 - 91 C4

 

[Schrade]

A perfectly tuned original C4 motor is awesome - LT1, L98, X-Fire too. Know why? Cause hardly anybody keeps 'em tuned right.

If your motor is worth a few bucks, sell it, buy FSM, ALDL scanner, fuel pressure gauge, multimeter, and proper tools for tuning your vette.

Diagnosing and fixing a problem burn in a vette is fun, and makes you a better thinker and problem-solver. Smarts ALWAYS goes farther than $$ too.

That's my opinion...

 

[vetteoz]

there must be an adapter from optispark connector to HEI??

No there isn't because the Opti uses a reluctor wheel which the HEI doesn't .Completely different electronics

 

[vetteoz]

I have herd the HSR will not fit udder the hood.of a C4. it would have to be the front section of the hood?

My turbo project

Holley Stealth Ram C4 L98 Version

 

[893508]

A perfectly tuned original C4 motor is awesome - LT1, L98, X-Fire too. Know why? Cause hardly anybody keeps 'em tuned right.

If your motor is worth a few bucks, sell it, buy FSM, ALDL scanner, fuel pressure gauge, multimeter, and proper tools for tuning your vette.

Diagnosing and fixing a problem burn in a vette is fun, and makes you a better thinker and problem-solver. Smarts ALWAYS goes farther than $$ too.

That's my opinion...

would you sell this engine?????
here is a link of my engine in a 89 TA 0 - 110 <>sloppy cameraman note the spedo
another of me vs A STI just as fast as a LT1<> notice the gap in less then 2 sec

YouTube - 89 trans am 357 holley stealth ram

YouTube - trans am messing with a sti

it would take alot of work to make any LT1 remotely close to my engine..
My buddy has a C4 & C5 his C5 can beat the first gen Z06. I can beat him
with my 5speed vs his 6speed
my engine deserves a C4

 

[Rex S]

Since your car will be a 94 does it still need to smog? If so you can't go backwards with an engine swap, only newer engines are allowed. To big of a visual difference in an LT1 & and L98.

 

[Schrade]

would you sell this engine?????
here is a link of my engine in a 89 TA 0 - 110 <>sloppy cameraman note the spedo
another of me vs A STI just as fast as a LT1<> notice the gap in less then 2 sec

YouTube - 89 trans am 357 holley stealth ram

YouTube - trans am messing with a sti

it would take alot of work to make any LT1 remotely close to my engine..
My buddy has a C4 & C5 his C5 can beat the first gen Z06. I can beat him
with my 5speed vs his 6speed
my engine deserves a C4

I'm sure it's a nice setup.

Power is addicting - you get some extra, next thing - you want MORE yup.

Someone else already has more UH huh. There'$ no end to that race. It can get you broke, and in trouble.

Anybody can bolt on parts, but who can TUNE a motor ? A clean burning, un-carbon fouled motor, dialed in with a scanner is a winner EVERY time.

That's just me tho'...

 

[893508]

Since your car will be a 94 does it still need to smog? If so you can't go backwards with an engine swap, only newer engines are allowed. To big of a visual difference in an LT1 & and L98.

NY the 94 is exempt
I have been tunning for 6 years
if you looked @ the vid there there is a AFR meter installed
my plugs burn perfect and here is a vid to show my tune cold day start no
pollution of any kind

YouTube - start idle rev walk

there must be a way to install the 91 PCM and engine harness in a 94
witch i know will go in it's all under the hood.. the ignition can not be that much different

 

[893508]

I'm sure it's a nice setup.

Power is addicting - you get some extra, next thing - you want MORE yup.

Someone else already has more UH huh. There'$ no end to that race. It can get you broke, and in trouble.

Anybody can bolt on parts, but who can TUNE a motor ? A clean burning, un-carbon fouled motor, dialed in with a scanner is a winner EVERY time.

That's just me tho'...

I may be new in here but!! but what kind of response is this above???
I'm positive it's a great setup!!! more then just bolt ons
my rods are minus 3 +LBS total.. floating pins, drilled to oil the wristpins,
zz4 crank. complete balance assembly, the HSR I modified to accept a 1206 race port to match my 1206 patriot heads, I built my own fuel rails, moded my own AFPR all -AN lines
and of course you alway's want more HP. but why start from scratch when you already have a dialed start

 

[vetteoz]

the ignition can not be that much different

Read my lips. Optispark is completely different.

 

[vetteoz]

there must be a way to install the 91 PCM and engine harness in a 94

Best way would be to install standalone harness for 91 ECM for engine management only ;keeping 94 wiring for dash and functions like A/c

1990-92 TPI Fuel Injection Wiring Harness : eBay Motors (item 190388418393 end time Apr-18-10 20:15:00 PDT)

 

[gmjunkie]

Best way would be to install standalone harness for 91 ECM for engine management only ;keeping 94 wiring for dash and functions like A/c

1990-92 TPI Fuel Injection Wiring Harness : eBay Motors (item 190388418393 end time Apr-18-10 20:15:00 PDT)

 

[Schrade]

NY the 94 is exempt
I have been tunning for 6 years
if you looked @ the vid there there is a AFR meter installed
my plugs burn perfect and here is a vid to show my tune cold day start no
pollution of any kind

YouTube - start idle rev walk

there must be a way to install the 91 PCM and engine harness in a 94
witch i know will go in it's all under the hood.. the ignition can not be that much different

You can do anything you want to do uh huh.

You have no idea how much work will be involved NOPE. I'm not referring either to dropping the motor into the mounts, or matching up the tranny.

I'm talking about re-pinning connectors (not just unhooking a harness). The PCM alone has 128 pins in the 4 harness connectors. A few are not populated.

To do what you want to do, done right, you'll have to SIFT your way through the FSM and identify the pinouts YUP. Take a good look at the diagrams that oz posted. I know them WELL uh HUH. And there's LOTS more where they came from. Count on having to pull a few dozen at the ECM. Then there's the CCM in the dash, which relays info from the ECM, through the CCM, and then some of that info goes to the gauges (more connectors to identify and re-pin), and don't forget the ABS module, and DERM module, and a few others too.

I built a computer once, and had to re-pin the front panel harness power connector to the motherboard interface. 3 pins out of 7 in the 8-socket connector. It took me an hour to get the connector pin ID's, and pull the wire ends out of the connector without breaking the spring locks, and get them in the proper sockets. I can not imagine trying to do this at the CCM harness connectors, and a few other places. hnoeshnoeshnoes I can show you pictures of tracking an LT1 harness, complete with backprobes of ECM connectors. I'd rather do retirement planning than do that again YUP.

Of course, you can just gut everything, and have a motor, tranny, and some analog gauges, and a few hundred feet of copper wire just riding along with ya' not doing anything...

 

[893508]

Ok Now !!! were getting some better feed back
I enjoy working on all electronic projects
I'm very comfortable with wires and harnesses. I have plenty of practice on fbody's and working in the cable field and network and optical cabling field
schematics are easy enough. my profession is in IT.
tracking wires using a toner & multimeter and looking at the pine-out schematic makes life easy!!!
so in your opinion would you install the stand alone or do the re-pin
the ABS is on its own management..
If I gut all the wiring should I wrap that around my exhaust tip like wedding streamers at least I'll be grounded
Im just kidding


thanks for some of the tips

You can do anything you want to do uh huh.

You have no idea how much work will be involved NOPE. I'm not referring either to dropping the motor into the mounts, or matching up the tranny.

I'm talking about re-pinning connectors (not just unhooking a harness). The PCM alone has 128 pins in the 4 harness connectors. A few are not populated.

To do what you want to do, done right, you'll have to SIFT your way through the FSM and identify the pinouts YUP. Take a good look at the diagrams that oz posted. I know them WELL uh HUH. And there's LOTS more where they came from. Count on having to pull a few dozen at the ECM. Then there's the CCM in the dash, which relays info from the ECM, through the CCM, and then some of that info goes to the gauges (more connectors to identify and re-pin), and don't forget the ABS module, and DERM module, and a few others too.

I built a computer once, and had to re-pin the front panel harness power connector to the motherboard interface. 3 pins out of 7 in the 8-socket connector. It took me an hour to get the connector pin ID's, and pull the wire ends out of the connector without breaking the spring locks, and get them in the proper sockets. I can not imagine trying to do this at the CCM harness connectors, and a few other places. hnoeshnoeshnoes I can show you pictures of tracking an LT1 harness, complete with backprobes of ECM connectors. I'd rather do retirement planning than do that again YUP.

Of course, you can just gut everything, and have a motor, tranny, and some analog gauges, and a few hundred feet of copper wire just riding along with ya' not doing anything...

 

[vetteoz]

my profession is in IT.

Get your head around this
http://www.gmhightechperformance.co...ion_system_understanding_modifying/index.html

http://www.teamzr1.com/ubbthreads/ubbthreads.php?ubb=printthread&Board=13&main=450&type=thread

and work out how to make '94 PCM work with the signal coming from a HEI

 

[Schrade]

I enjoy working on all electronic projects

When the project is on a desk in front of you, it's cake uh huh.

schematics are easy enough.

IF you have them. Putting an LS1 in a C4 in place of an LT1 is hard enough, EVEN IF YOU HAVE BOTH FSM's, to do proper re-pinning uh huh. And on top of THAT, you HAVE baseline operating parameters of LS1 and LT1, to write new code to the computer. If you have a 'homemade' twister, you probably have no idea what baseline data is for it ( I don't mean dyno numbers ), unless it was written by a professional tuner - stuff like injector pulsewidth, fuel trim cells, stepper counts for IAC, ignition - another whole story too YUP

so in your opinion would you install the stand alone or do the re-pin

I can't give you an answer to that Q - I wouldn't even think about it. With the harness out of the car, or with the harness in place, it would be a gargantuan task. You have to remember half of the connectors are reversed as you look at them, AND keep the pins in order when pulled, and tagged and labeled. If any are shorted, or if you miss the wrong one, woe is who??? hnoes

2 other things come to mind thinking of this task - shuffling cards till they were IN ORDER, and stirring my bowl of alphabet soup til I see my name and address spelled out.

If you do it, set up a website on your own server, with continual photo updates. You'll generate lots of webhits, and might make some $$ with ad revenue. Some of my photo threads have accumulated about 24k hits in forums.

Good luck on it...

 

[Schrade]

Just in case you're not knowing (or anybody else) what I'm referring to - re-pinning connectors, here's an idea (because I have to do it again, since I'm doing it AGAIN for a new PC build, as we speak):

Here's schematics for each front panel interface (from, and to):

... and this is the harness that we're having to re-pin - nice and open, easy to get to - really, compared to harness connectors in some places in C4:

Note the little tiny access holes in the side of the connector, for pushing out the locking spring tabs of each wire. I've NEVER seen holes like that in vette harness connectors nope. You have to pull them from the ENDS uH HUh, WHILE THE PIN IS IN THE HOLE WITH THE WIRE, AND THE TAB YIKES!!!! hnoes Both connectors, all over the car :eek !

But don't let me discourage you there now...

 

[boomdriver]

Has anyone called PainLess wiring for adptors & harness sections? THEY can help....conversions are the specialty.