I am Re posting this from Reddit and ill slightly modify what I said and have verified myself,


I have been trying to get this car to run it sat for a few years but did start, drove just fine until starter died so couldn't start it at all, I have replaced many parts on it and learned many things working on this car, me and dad, I am not a mechanic but am trying to learn but I need someone to help who knows how to work on cars

Car: 1989 Pontiac Firebird formula 350 Engine : 5.7 Fuel injected L98 (stock)

(First part of video) So the issue is that whenever I try to start my firebird, it would not idle with the MAF sensor connected, it would try, somewhat idle for a second but die,

(Second part of video) Whenever I would disconnect said sensor the car would still struggle a little to start when cold but if i tap the gas, it would idle but I think its on limp mode because if i try to put in drive or reverse its very weak on power

(Strange note: if I let car warm up for a little bit with MAF disconnected, then shut off, Conncect MAF it would struggle to start but then idle, still with weak power)

I have replaced many parts I might have lost track but here is what I have done myself

MAF + MAF RELAY

FUEL FILTER

ENTIRE DISTRIBUTOR SHAFT AND CAP

SPARK PLUGS AND WIRES

(For these 2 I have not calibrated or set but even unplugged it doesnt change behavior)
*IDLE AIR CONTROL

*THROTTLE POSITION SENSOR (I recently did fuel pressure test and it marked 40~ psi and did a smoke vacuum test and found nothing)

I did also do a weird test where i would start car with MAF connected, but the throttle intake duct not attached, if I brought the intake that connects MAF to intake close to the MAF it would sense air and engine would stall, could this be the MAF? Because I replaced it with a quality Delphi 250$
please help if you are a mechanic I've been trying to fix since 2021 but with school and work its become impossible for me and want to give one final attempt before I admit defeat and send to a shop

 

Do you know how to, and have you checked for codes? Start there

 

Get TunerPro software. One version is free and the better one is a donation of like $40. Need a cable he lists on his website for like $60 I think.

You can also jumper pins A and B then count the flashes. it will flash the same number of times then flash like 3 times then 4 times for a code of 34. This repeats until all codes are given. When it repeats the same flashing sequence as first you have received all the codes.

Also be on the look out for vacuum leaks. I had a plenum gasket leaking and it sounds similar to what you’re describing. Tape off the intake, disconnect the vacuum hose to the brake booster and blow cigar smoke into it. If you have a leak you’ll see smoke coming from somewhere. That’s how i found mine.

 

I think if flashes 12 like 3 times at first. One flash then 2 flashes.

 

Chevy Camaro 1982-1992 Factory Speaker Upgrade Kicker DSC46 DSC693

 

The donation, while a nice gesture, is not strictly required. If you just download TunerPro RT without donating for the license, you'll just have to wait 10 seconds on startup; works all the same after that 10 second window. I wouldn't jump to TunerPro right away either, since you would also need the ALDL Cable/ the processing box; no need to overcomplicate things just yet. If you plan to keep the car for awhile and plan to keep the stock ECU, then yeah you might want to look at Moates for the ALDL stuff, it is nice to be able to datalog. For troubleshooting like you're doing now though, you can probably just get away with reading trouble codes using the pin jumping trick on the OBD connector. Can't remember which two pins you wanna jump, Google can tell you, but basically just unbend a paperclip and use it to bridge the pins. Then, you turn the key to run (don't start the car) and count how many times the Service Engine Soon light flashes.

I believe code 12 is what will flash first to let you know it's in diagnostic mode. It'll flash once, pause, then flash twice, and pause again. That'd be code 12, and that just means you're in diagnostic mode; any saved trouble codes will start flashing after that. If it was, just for example, code 34, then after the pause following code 12, it'll: flash 3 times, pause, flash 4 times, pause.

 

I used both methods and liked Tunerpro to see sensor feedback, idle speed, etc. came in handy for that.