Chevy TBI tuning help

[Racer71]

Assuming it’s the 7727 pcm? I put together a few of those s10’s that way back when. You could direct swap it all, only thing actually different was distributor. Moates, sadly just closed, would’ve been your best solution for the ability to re-burn those old proms. Misfires at idle were typically the reluctor in the distributor getting cracks in it, that was common across all those gm dizzys back then. Make sure your coolant temp sensor is reading correctly and that the grounds at the thermostat are good. They would corrode in the crimp where it wasn’t always visible that caused issues. Also the passages under the throttle body that supply vac to the map sensor can get nasty with carbon/sludge and give inaccurate reading to map sensor

[Schurkey]

I'd expect all the GM TBI injectors to have the same resistance...but not the same gallons-per-hour rating. The 4.3L throttle body has the same airflow as the 5.7L throttle body, but not the same injectors. I'd expect the 6-popper PROM to be a problem, too.

There's multiple throttle body designs, with corresponding gasket changes. Be sure you have the right base gasket for the throttle body being used. Two examples, with gaskets and gasket part numbers:

5.7_TBI_original_sm.jpg

5.7_TBI_newer_sm.jpg

As said, the TBI distributors have a known problem with the magnets on the distributor shaft. They crack, generally across one or more of the rivets holding the assembly together. Most folks replace the distributor; but there are aftermarket distributor mainshaft assemblies. They may be getting kinda scarce by now. I think they're long discontinued by GM.

This magnet is cracked through the rivet in the lower right.

DSC_0015.JPG

And a new mainshaft for comparison:

DSC_0017.JPG

Verify fuel pressure. Spec is 9--13 psi, folks think they run better on the higher end of spec. But that of course assumes that the right injectors are in place, and the computer knows what engine is installed.
Connect a scan tool, verify ALL the sensors, and the computer outputs. Codes can be useful, the real info is in the data stream.

[Truckedup]

Here are photos of the ECU..The seller told me again that this ECM and the TBI are on the 350 swap engine were original parts on this S10 when it was 4.3 5 speed, still a 5 speed....

[juuhanaa]

Errr i dont know if the 6 popper prom is a lure or something but anyway if anyone is considering a fishing trip, i think the meps 3 is a good "flash".



-juhana

[Truckedup]

more info.....the service number on the ECU 16144288, is a dedicated 4.3 unit and will not support the V8.....so a V8 ECU and prom is required..........
I keep looking at the carb , intake and distributer in the corner of the shop.....But I am determined to use this TBI...

[rebelrouser]

more info.....the service number on the ECU 16144288, is a dedicated 4.3 unit and will not support the V8.....so a V8 ECU and prom is required..........
I keep looking at the carb , intake and distributer in the corner of the shop.....But I am determined to use this TBI...

Just buy a used V-8 computer and prom, check the wire pins on the connector to see if they go to the right places. One issue might be the cam and crank sensors. Cam sensor triggers at TDC the 6 cylinder computer then looks to see 6 pulses of the cranks sensor. It uses this relationship to set timing and fire the injectors. So when the computer sees 8 cylinder pulses before the nest cam pulse it may be confused about what to do.

[FC-Pilot]

If I did not need the factory ecm I might go with a micro squirt. The little brother of the mega squirt. The unit is relatively inexpensive and have heard good things about the software. It would run the TBI without an issue.

Paul

[dfarr67]

Modified 7747, factory harness- FTW

http://www.dynamicefi.com/

[FC-Pilot]

Modified 7747, factory harness- FTW

http://www.dynamicefi.com/

Looks like a pretty decent option.

Paul

[mt-engines]

Modified 7747, factory harness- FTW

http://www.dynamicefi.com/

Looks like a pretty decent option.

Paul

I have used a few of of bobs EBL Flash computers. Boosted, N/A driver stuff. Its quite advanced for the era.

With a wideband you can autotune. Lean cruise, electric fan outputs.

[Truckedup]

more info.....the service number on the ECU 16144288, is a dedicated 4.3 unit and will not support the V8.....so a V8 ECU and prom is required..........
I keep looking at the carb , intake and distributer in the corner of the shop.....But I am determined to use this TBI...

Just buy a used V-8 computer and prom, check the wire pins on the connector to see if they go to the right places. One issue might be the cam and crank sensors. Cam sensor triggers at TDC the 6 cylinder computer then looks to see 6 pulses of the cranks sensor. It uses this relationship to set timing and fire the injectors. So when the computer sees 8 cylinder pulses before the nest cam pulse it may be confused about what to do.

I just got a V8 box and 5.7 manual trans prom on Ebay from a guy who seemed to know something....Like rebelrouser just said, check the wires, some may need to be repinned ....So then I got a genuine GM wiring troubleshooting and wire diaghram manual so no guessing....
The engine runs like you say, confused, sounds like it's randomly dropping cylinders..But it does start and move the truck...
The truck is in our garage...My drive in heated basement shop is around the other end of the house...No real driveway just an off camber area of lawn. The shop is really for my bikes... the door opening is 69 inches, the truck is 65 inches wide...There is a few inches of snow,2 wheel drive shit traction truck.Probably have to drag it close with the utv and have to winch that lump in with a Come A Long.......My wife likes to help with this sort of show.....

[In-Tech]

Good evening folks,
Wow how the interweb and forums can be a thing

As noted, it appears you could get a 1989 or 1990 1227747 computer with hopefully a stock 350 manual trans eprom chip and the correct "limp" chip also, should be close. The v6 16144288 has a soldered in "limp", so, if you were to install an 8 cylinder eprom, it would immediately fail and run off the limp chip. Basically, no bueno.

I was thinking a '95 350 stick tbi ecm and chip would be better. I was still researching whether that had an electronic or solenoid controlled egr(these things can be corrected as well) among other things. I don't know if you care about shift light parameters either.

The other white box in your pics is the drac module which is for the speedometer. You shouldn't have to modify it but can be done if necessary.

You definitely still have to change the injectors and egr flow or modify the egr parameters in the chip.

If you end up with the 1227747 ecm, I hope the guy started you with an ASDX eprom, this is a 350 manual calibration.

Here are some notes of what's in the eprom, and an image of the eprom in hexadecimal.bin format.

ASDX.rar

ASDX_HAC.rar

.

Good Luck

[Truckedup]

In Tech, Ebay guy recomended a 16146299 computer and a 1992 manual trans prom, he didnt mention the number.......I should have been more clear,I did not order the parts yet from Ebay,just checking around, ...I was also waiting for your response.....If you have a better set up I do want to business with you. I trust your experience he more than the Ebay guy.I see from your reply he may seem to know something because I know a lot less...lol......Shift light is not important and egr only if needed to run properly...No emissions inspection in NY for vehicles over 25 years old.....

[In-Tech]

In Tech, Ebay guy recomended a 16146299 computer and a 1992 manual trans prom, he didnt mention the number.......I should have been more clear,I did not order the parts yet from Ebay,just checking around, ...I was also waiting for your response.....If you have a better set up I do want to business with you. I trust your experience he more than the Ebay guy.I see from your reply he may seem to know something because I know a lot less...lol......Shift light is not important and egr only if needed to run properly...No emissions inspection in NY for vehicles over 25 years old.....

Hiya,
The 1992 '6299 is a newer '87-91 '7747 and will have the limp chip soldered in for a v8 as well. Still not a bad choice. EGR is never a bad choice for fuel economy and emissions. It will not affect full throttle HP. The computer just needs to know if it is present and then the tune accordingly.

I appreciated your PM earlier yesterday and I apologize for not answering immediately, was just busy as usual

[In-Tech]

Hiya Everyone,
I have to look through my stash of ecm's. I am pretty sure I have I have some stuff for Trucked that will be "plug and play" when I finish it.

I started doing efi tuning way back in the early 90's and gradually moved away from engine building to do more efi stuff, probably before his v6 Truckedup S10 was born. I just don't move as fast as I used to...I think there's a song, as good as I once was

I'll send the complete puter in a dry ice box when I get it figured so you can get your local ice fishers to return with a couple fresh trout

btw, the dynamic ebl is a great option. Since the engine is stock, it doesn't seem like we have to go that far.