To the op, has the spray pattern been checked for dripping injectors ? You can use a timing light to strobe and see the spray pattern . I forgot if the tb was gone through.

 

@Tuned Performance The spray pattern is a really nice conical shape (I think that’s the correct term) no dripping whatsoever. I rebuilt the entire TB with an AC Delco rebuild kit. Brand new AC Delco injectors too. I put a really bright LED behind the TB when I rev and it looks to keep shape. Is that normal? Again, it’s so hard to test all this and see the shape of the TB spray when driving under load.

But when I I throw in gear on jack stands the shape of the fuel spray out of the injector seems to stay the same.

I may rig up a temporary good ol boy exterior gas tank with an external pump with large size fuel line to bypass my current fuel system to rule it out.

 

He said that he put new injectors in it.*

Couple things:

1. TCC won't cause the symptom that you're sharing with us.
2.Spec for TBI fuel pressure is 9-13 PSI. All TBI that *I* have played with definitely "like" the fuel pressure on the high side of spec, or even above spec (same with ignition timing). Your drop in pressure isn't going to a point or place where it's below OEM spec....but my issue with what you shared above is that the TBI fuel pressure shouldn't BUDGE AT ALL, from idle to WOT at red line. If it's 14 PSI at closed throttle idle? Then it should be 14 PSI running down the drag track, too. So...why is your pressure dropping? RED FLAG.
3. I like what Dyno Don asked about where your MAP sensor vac signal is coming from. I've been thinking about the MAP sensor for a while now, and that is what lead me to ask if you have a (decent) scan tool, where you could watch the MAP sensor (among other things) while it's running.
4. You don't need a timing light to see the spray pattern. It helps, but not necessary.

 

like I said , seen many posts didn’t recall the first page, dyno don posted on here ?

 

@DynoDave43 @Tuned Performance @Tom 400 CFI

Thanks everyone - great input. The needle does move a hair under load (still within factor spec). But like you guys mentioned - it shouldn’t move at all:

Someone mentioned that the new stainless steel braided fuel lines may begin to constrict under fuel demand? That’s hard to believe since I know friends that drag race that use the same lines. Also me being a contractor I know that a 60-100 pound water psi test doesn’t cause a plumbing pipe to expand. Why would 12-14 psi cause a 3/8’s line to constrict? (Me just spitballing here)

I’m hopping on the theory that it’s starving fuel - just how is what baffles me, especially with the new fuel pump, filter, lines, regulator, etc. the car seems to stumble when accelerating.

As for the MAP sensor - it’s mounted in the stock location in the passenger firewall. The vacuum hose is brand new and it hooks to the vacuum port on the back of the throttle body. I am interested to run a scanner on it now, although that is brand new as well.

 

@Tuned Performance I’m getting ready to order this.
https://shop.moates.net/products/aldu1-and-cabl1

Want to make sure this is everything I need. Minus tuner pro and adx file.

I’m thinking this will be very valuable to have since I plan to keep this car around.

Appreciate the recommendation!

 

That’s correct, if you need setup help or a adx for tuner pro rt lmk.
I would do a engine fully warmed up log and zip it and post here.

 

Can you confirm that the vac port that the MAP is hooked to is manifold vacuum and not ported vacuum?

 

@Tom 400 CFI so the MAP hose is connected to the vacuum port labeled “F” which is the only one on the back of the throttle body. It’s really hard to tell if it’s below or below the throttle plates because it’s almost exactly even with it. Take a look at the pics.

thanks!

 

Can you put a vacuum gauge on it to confirm what kind of port it is?

OR, if it's easier, could you cram the MAP hose into the brake booster hose, for a minute, start it up and see if it runs better?

 

@Tom 400 CFI so I just tested the map sensor vacuum connection with a vacuum gauge the pressure held / vacuumed at a consistent psi, it remained with good pressure during warm up and warm idle. Not quite sure in load acceleration. Any specific psi the vacuum should be held at?

I’ve tried to plug these ports with vacuum caps (all except for PCV vacuum port) and it still has the same issue during acceleration.

Also, @Tuned Performance I was able to confirm their is no lack of fuel delivery from pump, filter, or regulator.
I was able to install another pressure gauge right before the TB dedicated to the supply line and it stays right at 13-14 even in hard acceleration in gear. I’ve got a good video showing this - I’m going to upload on YouTube.

https://youtube.com/shorts/0djLmpcht_k?si=BH8jTeqZ3Nu2IUtM

thanks

 

Should be ~20" at idle, 0" at WOT. Probably drop as low as 8-ish, when you crack the throttle to rev it a little.

 

There is only one vacuum port on the back of the TB for my 1992 L03 TBI Firebird. It's the vacuum port the MAP sensor connects to. It's full manifold vacuum.

 

So where's the fuel pressure regulator? I see the return is capped off. It should be after the injectors on a system like that.

 

You can see it on the fender, in the vids. It CAN be hooked up "before" the TB, but attention does need to be given to how it is plumbed for it to deliver the right pressure to the TB. Basically, your "T" need to be before the regulator; whether that be internal passages in the reg or whatever.

I thought for SURE, that plumbing was the issue and the TB was only seeing incidental pressure but the OP says he check pressure at the TB and it was 12-14ish. So, w/o being there, I'm skeptical...but I'm not there.

 

@ex-x-fire @Tom 400 CFI

So the return is not capped off, that’s the performance vacuum line (not used for this situation)

The return line back to the tank is the bottom port.

The supply line from the pump is the right port.

The the supply line TO the Throttle body is the left port.

That secondary gauge you see is directly in front of the throttle body to confirm pressure at idle and WOP.

I will sketch up a diagram of how I have it plumbed so people can cancel out my “plumbing” and the fuel pump and filter.

Thanks

 

where the primary guage is at in my YouTube video. That posted prior.

 

@Tom 400 CFI thanks for this! Will check tomorrow.

 

To the OP. Just wondering if you've made any progress. I'm little by little trying to rule things out, so I replaced the EGR valve and ignition coil today. Took it for a test drive and lost power (as in no acceleration) until it died. It died on me again about 3 or 4 times until I came home. Back to square one

 

@Miketee So I after checking everything up and down for days - after speaking with some of the more experienced third gen guys - I ordered this scanner / data collector tool. Downloaded TunerProRT and the proper files associated with being able to do a live data scan collection.

https://shop.moates.net/products/aldu1-and-cabl1

I emailed them off to @Tuned Performance and he is in process of analyzing everything.

I also uploaded my data log to an AI software and the AI analyzed it as well - it is fairly certain it’s Ignition Reference Signal loss. Here are the symptoms. (See attached PDF, make sure you read the whole document!)

Also, TunedPerformance mentioned the O2 sensor might be reading erratically - so I ordered a 3 wire heated O2 sensor which is recommended with headers anyway.

I’ll keep you posted as I hone in on the outcome!

 

After doing some research, I've seen that replacing the ECM has fixed the issue on some Firebirds but more research is needed on that because apparently there needs to be some programming done. It's not just plug-and-play for the ones that run +/- $100. The preprogrammed ones can run several hundreds. I didn't see that on your list of parts you've replaced so I'm wondering if you ruled that out. I'm gonna replace sensors and check my vacuum hoses before I get to that points. Also, I don't have a check engine lights on so I'm still pretty lost on this project.

 

a replacement 1228746 you just swap over prom and calpak. I’m not thinking it’s the ecm in this case. The datalog shows ref pulse intermittently flashing like it’s missing occasionally. Off cts has two readings in the $61 adx I used one shows what appears to be right the other is around 80f.

 

I have no idea where you got this information from but it's not correct.

You disconnect the negative battery cable, remove whatever is necessary to get to the ECM behind the passenger side kick panel, remove the electrical connectors from the ECM, remove the ECM from the mounting points, remove the two screws to remove the cover to access the Memcal, carefully remove the Memcal from the old ECM and carefully seat it fully into the new ECM then go in reverse order and put everything back like it was and reconnect the negative battery cable, then start the car.

 

I missed Tuned's reply before I posted mine. I had to take a leak then I made me something to eat in the kitchen. Came back and finished my reply and posted it.

 

Not sure if you got your Firebird up and running yet, but I think we got ours fixed (for the time being, at least). It turned out it was the sending unit. The mechanic showed my dad where the wiring was damaged on the sending unit, so we're pretty sure that's what it was, but we did also get the tank and fuel pump replaced along with it. Hope that maybe helps you a bit since I didn't see that on your list of parts you replaced. Good luck to you.