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1991 Firebird ecu problems

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Old 07-17-2018, 03:23 PM   #1  
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1991 Firebird ecu problems

my 305 tbi. Spun a bearing. I replaced with a 350 tbi from truck. I donít now if I repin truck computer or change chips. In old computer. I have researched. And Iím no good at it. Thanks in advance.

350 tbi 700 auto 2000 stall long tube headers open exhaust open intake. Stock cam heads.

I have a 1227747 ecu asdu chip and a 1228746 ecu (original ecu)

can i I repin for 747 ecu. Or do I have to find a chip for the 746 ecu

Last edited by Dan Baker; 07-17-2018 at 03:29 PM.
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Old 07-17-2018, 03:37 PM   #2  
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Re: 1991 Firebird ecu problems

If you want to try the '7747 ECM, no need to re-pin. Unplug the '8746 and plug in the '7747.

There are 5.7l Caprice chips available for the '8746 ECM.

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Old 07-17-2018, 03:54 PM   #3  
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Re: 1991 Firebird ecu problems

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If you want to try the '7747 ECM, no need to re-pin. Unplug the '8746 and plug in the '7747.

There are 5.7l Caprice chips available for the '8746 ECM.

RBob.
I did. Iím getting a code 22. TPS sensor. And with stock 305 tbi ecu. Runs like crap. But even worse with the 747 ecu
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Old 07-17-2018, 06:24 PM   #4  
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Re: 1991 Firebird ecu problems

It has to be bad ecu and or tps. Iím looking at wiring schematics. This computer should work.
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Old 07-17-2018, 07:32 PM   #5  
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Re: 1991 Firebird ecu problems

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Originally Posted by Dan Baker View Post
my 305 tbi. Spun a bearing. I replaced with a 350 tbi from truck. I don’t now if I repin truck computer or change chips. In old computer. I have researched. And I’m no good at it. Thanks in advance.

350 tbi 700 auto 2000 stall long tube headers open exhaust open intake. Stock cam heads.

I have a 1227747 ecu asdu chip and a 1228746 ecu (original ecu)

can i I repin for 747 ecu. Or do I have to find a chip for the 746 ecu
I have a few atjp proms from the caprice 350 automatic transmission
https://www.thirdgen.org/forums/engi...tbi-350-a.html


Last edited by RBob; 07-18-2018 at 11:02 AM. Reason: undeleted as this isn't the DIY_PROM board
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Old 07-17-2018, 08:11 PM   #6  
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Re: 1991 Firebird ecu problems

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I did. Iím getting a code 22. TPS sensor. And with stock 305 tbi ecu. Runs like crap. But even worse with the 747 ecu
Fix the mechanical issues first. Then start looking at the ECM. As for using a TBI 305 versus TBI 350 PROM, there will be some differences but not to the extent that you are seeing.

RBob.
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Old 07-17-2018, 08:46 PM   #7  
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Re: 1991 Firebird ecu problems

Yep
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Fix the mechanical issues first. Then start looking at the ECM. As for using a TBI 305 versus TBI 350 PROM, there will be some differences but not to the extent that you are seeing.

RBob.
yep. Iím looking for donor ecu the tps signal not coming from ecu. Schematics look identical on a 299 board. I found one on eBay. The info. On this site is amazing. Thanks for the replies I will update.
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Old 07-17-2018, 09:23 PM   #8  
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Re: 1991 Firebird ecu problems

Here is a stated working condition ecm
https://m.ebay.com/itm/89-91-Firebir...from=R40&rt=nc

Just curious is it the 5v ref that’s not working ?
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Old 07-17-2018, 11:04 PM   #9  
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Re: 1991 Firebird ecu problems

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Here is a stated working condition ecm
https://m.ebay.com/itm/89-91-Firebir...from=R40&rt=nc

Just curious is it the 5v ref thatís not working ?
thanks thatís the one lol. Iím looking at my local jy. If not there Iím buying. Yes nothing from I think b13. 305 computer runs the car not to bad no ses light.
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Old 07-18-2018, 10:43 AM   #10  
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Re: 1991 Firebird ecu problems

I think you mean c13 , bummer but atleast you solved the problem. Going to a 350 a truck ecm might be the way to go because you can get the prom for a 350.
If you need the four letters identification decoded let me know. I have a program that tells what the broadcast code is from. Maybe rbob can say if the 746 ecm is better with the iat input or if the ecms are about the same.
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Old 07-18-2018, 12:05 PM   #11  
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Re: 1991 Firebird ecu problems

Sorry I didn’t see you have a asdu that might be a decent way to go with the 747.
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Old 07-27-2018, 07:14 PM   #12  
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Re: 1991 Firebird ecu problems

I got all mechanical issues solved. No ses. I have the 7747 ecu with the asdu chip. What I have is a 350 tbi all stock I believe I using ac. I have a 700r4 with 2000 stall. I installed a gu6 g80 rearend out of a 2001. Open headers into a cherry Bomb. I changed fuel pump. I changed to 14 psi spring.


the question is I need to tune. What do I buy. Itís 2018. Most post on tuning is from 2005. I canít read no more. What should I buy. Do I get someone else to tune. So I have a running car. It should be easier to tune. Do I have to use a 28 pin. Iím so lost. Any help would be appreciated
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Old 07-27-2018, 10:03 PM   #13  
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Re: 1991 Firebird ecu problems

You can still buy 2732a proms to reprogram but you would need a pocket programmer.
There is always the dynamic efi ebl system. Or look into moates.net burn 2 and adapter for using eeproms in your ecm.
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Old 07-27-2018, 10:11 PM   #14  
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Re: 1991 Firebird ecu problems

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Old 07-27-2018, 11:25 PM   #15  
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Re: 1991 Firebird ecu problems

I will be ordering the autoprom and g2 chip adaptor. Thanks again Im sure I will have more questions.
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Old 07-27-2018, 11:29 PM   #16  
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Re: 1991 Firebird ecu problems

What can I do about the speedometer being so off. Since I switch rearend gears. I can’t find much on that. I’m sure it’s here somewhere. So much knowledge here on third gen.
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Old 07-28-2018, 10:01 AM   #17  
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Re: 1991 Firebird ecu problems

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What can I do about the speedometer being so off. Since I switch rearend gears. I canít find much on that. Iím sure itís here somewhere. So much knowledge here on third gen.
Replace the yellow 4-OUT BUFFER box with an SGI-5 box and be done with it. The SGI-5 is user programmable to set the proper pulse train frequency.

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Old 08-07-2018, 07:29 PM   #18  
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Re: 1991 Firebird ecu problems

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Replace the yellow 4-OUT BUFFER box with an SGI-5 box and be done with it. The SGI-5 is user programmable to set the proper pulse train frequency.

RBob.
I have sgi 5e. How to wire.
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Old 08-07-2018, 07:54 PM   #19  
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Old 08-07-2018, 08:23 PM   #20  
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Re: 1991 Firebird ecu problems

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I found a wiring diagram for my vss. Do I splice in. Or wire in place of existing vss. Im just confused. Sorry for dumb questions. But Iím not finding much on how to wire. I want cruise and everything to work.
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Old 08-07-2018, 08:50 PM   #21  
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Re: 1991 Firebird ecu problems

If correction is needed for rear gears hook up the vss signal on the vss output on the sgi.
if no correction is needed it doesnít matter you could splice the input signal.
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Old 08-07-2018, 09:03 PM   #22  
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Re: 1991 Firebird ecu problems

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If correction is needed for rear gears hook up the vss signal on the vss output on the sgi.
if no correction is needed it doesnít matter you could splice the input signal.
Iím running alittle slow. Thanks. I need adjustment so I run from sgi signal to a10
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Old 08-08-2018, 07:07 AM   #23  
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Re: 1991 Firebird ecu problems

I take back what I said about replacing the 4-OUT BUFFER box. It would be easier to place the SGI-5 box between it and the VSS. Use one of the 4K PPM A/C output from the SGI box to feed the 4-Out buffer box. Much less rewiring to do.

The twisted yellow and purple wires are from the VSS. On the 4-out buffer note the connector with the YEL & PPL wires. The outer one is the actual signal, so cut it leaving enough room to splice to the two new ends. Leave the inner wire alone, it is ground.

Now run the outer wire from the VSS to the A/C input to the SGI box.

Then run a 4K PPM A/C output from the SGI box to the 4-Out buffer box wire that you cut.

Add power and ground to the SGI box, program it and it should all work.

RBob.
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Old 08-08-2018, 07:52 AM   #24  
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Re: 1991 Firebird ecu problems

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I take back what I said about replacing the 4-OUT BUFFER box. It would be easier to place the SGI-5 box between it and the VSS. Use one of the 4K PPM A/C output from the SGI box to feed the 4-Out buffer box. Much less rewiring to do.

The twisted yellow and purple wires are from the VSS. On the 4-out buffer note the connector with the YEL & PPL wires. The outer one is the actual signal, so cut it leaving enough room to splice to the two new ends. Leave the inner wire alone, it is ground.

Now run the outer wire from the VSS to the A/C input to the SGI box.

Then run a 4K PPM A/C output from the SGI box to the 4-Out buffer box wire that you cut.

Add power and ground to the SGI box, program it and it should all work.

RBob.
thank you. I will give it a shot. And I will report back.
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Old 08-08-2018, 11:52 PM   #25  
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Re: 1991 Firebird ecu problems

From experience you need to use shielded twisted pairs for the sgi-5 wiring or you will get the speedo bouncing when stopped.

GD
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Old 08-09-2018, 05:45 AM   #26  
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Re: 1991 Firebird ecu problems

The vss 4 out buffet was very difficult to find. I had to remove trim piece on passengers side. About knee high. Itís the piece above what you take off to acces ecu. Anyways I ran power wires from radio. Cut purple wire. Striped hooked up the end coming to board to sig in. And other end to out 1 on the sgi board. And just drove and set speedometer. Worked awesome. Thanks everyone. Now to finish my 2 din install.
As far as tuning the ecu. I burnt cable to autoprom from ecu. I must have soldered in adapter wrong. Strange though when I put my 24 pin chip. Back In and car runs fines. Autoprom. Works fine for monitoring. I have put several emails into Moates. With no response. I heard nothing but good things about Moates. I hope they get ahold of me. I will purchase ribbon cable again from him. But I think ribbon was made wrong. From beginning.
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Old 08-10-2018, 06:59 AM   #27  
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Re: 1991 Firebird ecu problems

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The vss 4 out buffet was very difficult to find. I had to remove trim piece on passengers side. About knee high. Itís the piece above what you take off to acces ecu. Anyways I ran power wires from radio. Cut purple wire. Striped hooked up the end coming to board to sig in. And other end to out 1 on the sgi board. And just drove and set speedometer. Worked awesome. Thanks everyone. Now to finish my 2 din install.
As far as tuning the ecu. I burnt cable to autoprom from ecu. I must have soldered in adapter wrong. Strange though when I put my 24 pin chip. Back In and car runs fines. Autoprom. Works fine for monitoring. I have put several emails into Moates. With no response. I heard nothing but good things about Moates. I hope they get ahold of me. I will purchase ribbon cable again from him. But I think ribbon was made wrong. From beginning.
Moates emailed back. I was powering laptop at same time as I was trying to emulate. It was explained to me this will back feed voltage or ground. So donít have laptop plugged in to a/c power. as you emulate.
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