Hi i am newbie but need help my thing is i have a 91 rs tbi car originally 305 now has 040 over 350 mild compucam 1.6 rollers performer tbi intake tbi 11/4 spacer 7.4 tb with 350 police injectors dyno dones y pipe american thunder 3inch exhaust thing is i put the 18psi regulatore spring in and installed a tpi fuel pump now i get a code 44 lean condition and car surges at cruising speed and has loss of power please help

 

You need to custom tune the EPROM. The factory EPROM is configured with narrow limits to run a 305 TBI. It cannot run your new combo at all. You will either need to tune DIY (search EBL) or take it to someone who knows how to tune EPROMS.

 

Try scott he does great work tuning cars not sure if he does tbi tho http://scotthansen.net/index.html

 

You can find another 1228746 ecm in the classifieds or on eBay for relatively cheap. Send it to moates.net and have them solder in a adapter and sell you a zif so you can use a newer flash chip.
you then could datalog with tunerpro rt and dial in fueling.
you can still do old uv erasable 2732a chips but will need a more expensive burner and uv eraser.

 

well i see people say needs custom tune but i had this engine in a 91 s10 4x4 same all but the tb unit using stock 4.3 v6 ecm and tbi ran great also my son has a 89 GTA with tpi using afr cylinder heads same exhaust big injectors adjustable fpr on stock ecm runs great sets tires on fire runs with ls cars

 

The ecm doesn’t just throw a lean code without seeing the o2 mv beliw .450mv for a extended period.
it doesn’t sound like your concerned about the right ecm calibration so just throw a 1227747 4.3l ecm and v6 calpak in there and see what it does. Not the magic fix.

 

From what I've read, the 454 TBI is overkill for anything mild. A mild 350 with 350 injectors is good, but the 7.4 TBI is letting a LOT of air in.

Don't know...just asking. Could this be the cause of the lean condition?

 

The 4.3 tune assumes larger injectors which is why it ran better. The L03 used smaller injectors than the 4.3 and 5.7 TBI cars. You have a tuning problem. Also, the timing tables for swirl port and non swirl port heads are completely different as well. Any EFI car needs tuning when veering from stock. There are countess folks out there who do all the right mods to their TBI motors but don't tune it, and it ends up being slower than stock.

 

Thing is ive been driving this thing for awhile with no ses light what changed was i put in the 18 psi regulator spring and switched to the tpi fuel pump if anything it should have made it rich not lean

 

The fuel tables in the ECM are controlling the fuel. The extra pressure and volume from your new regulator and pump goes right down the return line. You only increase those when the injectors need it to fuel the new combo, through tuning (duty cycle etc). Put the old spring back in to see if it runs better. You are also getting your lean condition from a cruddy narrow band OEM 02 sensor. Its not telling you what the motor needs. I would look into data logging first. Let the car tell you what it needs. You will see that it needs fuel and spark adjustments everywhere. Once everything is properly tuned, the engine should feel like a whole new animal.

 

Connect a scan tool, look at the data stream. Verify your fuel pressure. There's a dozen things that can cause the computer to think the engine is "too lean", among them are vacuum leaks, misfires, and faulty O2 sensor(s).

Yes, you probably need a custom tune. Me, too. I hate the thought of doing that, so I "get by" on the OEM stuff. The difference is that I'm not getting codes for fuel or spark. (I do have one for EGR, the EGR valve tests faulty and will get replaced a couple hours from now.)

PS: Use punctuation, capitalization, and proper spacing. Makes your posts easier to read. All of this was taught by fifth grade.