Hi I have a 91 firebird. You can start the engine and she will run great for about 15 seconds and then she will die. If i try to restart it after a few seconds it will do the same thing. On occasion it will idle, then rev to 2000rpm and she will just cut out. When it will not restart, it will keep cranking over and will occasionally make a popping sound from the intake manifold as if the timing is wrong, but the timing is set correct.
Ive done a fuel pressure test and it seems to be ok at 42psi.
I have changed the O2 sensor, Temperature sensor, Plugs, Rotor arm, Distributor Cap, Electronic pickup in the distributor and fuel filter. Tried different module and leads.
Ses light came on and i have got a code 45 reading for rich exhaust.
Can anyone possibly shed any light on this problem? What am i missing?
Thanks

 

First I will say, these cars aren't my best area of know-how.
I started and administer a site dealing with 2ng gen cars, but...
I own a 1990 Firebird with this engine, and have spent a little
time with it.
Two thoughts I have.
1) fuel injectors... are your's original?
2) The ECM. I had some odd hard to nail down issues that ended up being
the ECM.
When I tested it, I got the a-ok. Testing it just a day later gave me
every code in the book... a re-test moments like said all was well. The thing
was so messed up it couldn't even test itself properly! One rebuilt ECM later
and so very much had cleared up.
After the ECM, I found a TPS that didn't throw a code, but was barely
functional.
I also have an 86 TPI Trans Am that needed injectors bad, upon removing the
originals 2 crumbled in my fingers and a third separated in two. None of these
units looked anywhere near serviceable.
I hope some of this helps...
Joe

 

Thanks Joe, i will look into these and hopefully it will solve the problem. Ive only had the car for about a month and never expected these problems. I will post on here the outcome as soon as i know what it is. Many thanks

 

After further investigation and all of the ignition system components have been replaced, i have got a wonderful spark on the plugs, but it still will not start. I can hear the fuel pump run, pressure tested at 42 psi at the Schrader Valve, it appears no fuel is getting through (dry spark plugs). Spraying a bit of fuel down the plenum made it start, I dont want to replace the fuel pump if its not at fault (pressure test). Any ideas would be appreciated as to why no fuel is getting in.
When the car broke down it behaved as if it had run out of fuel...any ideas?

 

Well, I'm about 800 miles away from my '90 Pontiac
shop manual (on the road), and I don't remember this exactly,
but...

The engine monitors oil pressure, and if it sees no
(or very low) oil pressure it'll cut off the fuel. Now there
is an exception for starting "I think" somehow.

If you have fuel pressure to the rail, then all you'd need
is the electrical signal to the injectors to get fuel in
the cylinders.

Most auto parts supply houses sell those little test lights
that can check for the injector pulse. This might be an easy
way to continue to narrow down the suspects.

I'll bet that oil pressure switch is probably inexpensive,
something else that would help narrow things down.
(most likely a separate one from the dash gauge)

I assume you checked ALL the fuses right? (grin)

I'm home late Sunday night and will be in my shop
Monday after lunch and can get more specific info.

Keep us updated...

Joe

 

the fuel pressure should be at 65PSI, 42 is fairly low. this could be an issue, i have 69 PSI on my 85 camaro. at least this is what i have been told by Napa.

 

Hi
Thanks for the replies, it turned out that 4 out of the 6 injectors were not delivering fuel, so bought a set, changed them and now all working great.... Thanks for the ideas and glad my bird is finally on the road again

 

A few things wrong here:
1. NO WAY IN HE11 should a MFI or TPI system be running at 60+ PSI! If it did, the fuel system would have so many leaks the pipes would blow apart at the unions. Stock spec is 37-47 PSI. I think I've found another person falling for what the knowlegeless idiots at NAPA have said.
2. ECM does NOT monitor oil pressure! There is a fuel pump oil pressure switch that runs the fuel pump if there is a failure of the fuel pump relay (run by the ECM), but this will be evidenced by a code 54.
3. The Vehicle Anti Theft System (VATS) can and will disable fuel injection if there is an incorrect key resistance reading unless either bypassed or the ECM code has been modified to delete the VATS. The VATS will also disable the starter if this happens, so the problem doesn't appear to be VATS.

Glad you found the problem, though.

 

BTW, sixgun, where did you get your ECM tested? I can't find a place to test either one of my 730's.