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1994 Pontiac Firebird Formula LT1

 
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idabomb00 idabomb00
New User | Posts: 34 | Joined: 06/12
Posted: 06/24/12
06:55 PM

Okay so I had posted on here before about this car but I had fixed all my error codes besides the one with the A/C which I'm not worried about right now.

It runs pretty decently except when it's at a lower idle it kinda sputters, not really a miss. The code reader has INT_LEFT INT_RIGHT and the right side is less than the left side.

So far these parts I have replaced brand new:
Optispark distributor
All sparkplugs
All sparkplug wires
Coil
Fuel Pump assembly

I kinda suspect the fuel injectors but maybe somebody else has another idea...  

waynep71222 waynep71222
Guru | Posts: 825 | Joined: 03/12
Posted: 06/24/12
07:51 PM

print several copies of this chart.. there are numbers just out of view to the right...  

write your scan tool values down on the proper line..

copy as many as you can.. at idle.. and at 2500 RPMs..

then type them in...

you can also stop by a junk yard..  pick up a used fuel injector connector pigtail...


TPISCANDATA87

the block learn numbers and the integrator numbers when the engine is running good should be really close to 128.. when in closed loop...


this is what the fuel injector connector looks like..





GP Sorensen/Fuel Injector Wiring Connector
Part Number: 6414
Notes: Black. With centered index slot, without release.
Price: $6.29


GP Sorensen/Fuel Injector Wiring Connector
Part Number: 800-9213
Notes: Black. With centered index slot, with release.

you will also want to pick up some banana plugs from radio shack or another electronics store..



accessories

in the box

Stackable Banana plugs (2-Pack)
Model: 274-734  | Catalog #: 274-734
$3.49

then you can individually OHM the fuel injectors to check for shorted injector windings..

less than 14 ohms is a problem with the injectors...  burned out or shorted windings..  

idabomb00 idabomb00
New User | Posts: 34 | Joined: 06/12
Posted: 06/24/12
08:08 PM

Thanks for the quick reply.

The integrator numbers run at 128 on both sides when I first start up the car. Then after it warms up the left side is about 140's and the right is 120's at idle speed.

I will get the scan tool values to you and check the ohms on the injector windings tomorrow. Should I check the ohms with the battery disconnected or just off?  

waynep71222 waynep71222
Guru | Posts: 825 | Joined: 03/12
Posted: 06/24/12
09:18 PM

vacuum leaks..  on one side....  tiny ones...   off set integrator numbers...

does your car have air injection..  where you might have some kind of uncommanded air leak into the upstream air injection system..  even a tiny one..  a bad diverter valve..   lazy oxygen sensors...  or contaminated oxygen sensors..

disconnect only the injector plugs.. you don't need to disconnect the battery...

in case you find shorted injectors.. under 14 ohms...  there are sets of BOSCH III (design 3) injectors available from some suppliers cleaned and flow matched that people really swear by..  

idabomb00 idabomb00
New User | Posts: 34 | Joined: 06/12
Posted: 06/24/12
10:09 PM

I was thinking that it was a vacuum leak but this car has a throttle body, I don't think that'd off set the itegrator numbers off one side consistently.

My scan tool does show one of the oxygen sensors going all over the place, not at first but when it warms up and I don't know if it's normal. It may be consistent when the integral numbers get thrown off...

I'll have to check tomorrow.  

waynep71222 waynep71222
Guru | Posts: 825 | Joined: 03/12
Posted: 06/25/12
05:41 AM

there are still vacuum connections around the intake manifold.. and gaskets around the intake..


could the power brake booster be blown out.. and a constant vacuum leak..   does the brake booster hold vacuum for 20 seconds after shut down???/    when you hold your foot on the brake after pumping the vacuum out with the engine off...  does the brake pedal drop as you start the engine??

its a pain... but if you swap the oxygen sensors left and right...   see if the trouble follow the swap... that would indicate a sensor issue...

are any spark plug wires near the oxygen sensor wiring???

that model should have 3 wire oxygen sensors...  is the oxygen sensor voltage going above 0.9 volts?? if so.. follow the ground connection for that sensor...  loss of oxygen sensor ground will drive the ECM crazy as the heater element will try to send power up the signal wire...  

idabomb00 idabomb00
New User | Posts: 34 | Joined: 06/12
Posted: 06/25/12
03:57 PM

Sorry, I didn't get a chance to do the scanner tool today. I will jump on that tomorrow hopefully.

I'm pretty sure it doesn't have a vacuum leak so I'll do that last, but I did check the brake booster and everything checked out. The brake pedal drops when you start it and it holds vacuum 20 seconds after the engine shuts off.  

waynep71222 waynep71222
Guru | Posts: 825 | Joined: 03/12
Posted: 06/25/12
06:37 PM

is the idle smooth... could the EGR valve be leaking slightly???

i know its buried deep under the intake plenum..


exhaust leaks... allowing fresh air into the exhaust system during scavenging..

leaks in the air injection system..  internal or external.. internal would be from bad diverter valves.. external would be a loose hose.. rusted check valve housing..

sounds like you work in a shop .. do they still have their fuel injector tester that a LOT of shops bought in the 90s...  so with the key off.. you could prime the fuel pump.. hook up the injector tester.. and the fuel pressure gauge.. with a BIG gauge..   i usually use a remote starter switch to activate the fuel pump prime to bring the fuel rail pressure up till the regulator releases it.. so i have the same starting point each time...

i then push the button on the injector tester..  it sends 15 pulses  or 50 pulses... both equal the exact same amount of time in the ON position ... looking at the pressure drop.. and noting it exactly.. then you move to the next injector.. bring the fuel pump prime pressure up again.. then pulse the next injector..   when all 16 tests are done..   you will probably want to do this with the spark plugs out..    you are NOT spraying very much fuel..  so only a small chance of a cylinder full of fuel is possible.. but its still a chance..   you can use a big ratchet on the crank bolt to turn the engine a 2 full turns.. or more to verify no hydraulic lock..

i had the kent moore kit.. with the 8 connector adaptor harness and the knob in the box.. one of my bosses decided he wanted to replace some injector connectors.. got into my tool box and chopped the ends off my harness.. then threw the rest away..   i have not replaced it as the tester part of the kit grew legs and walked away.. leaving me with just a switch box..

with the low price of the injector connectors above... i might think about rebuilding it..  just for OHM testing..  and amp draw testing.. but thats a whole different subject...  

idabomb00 idabomb00
New User | Posts: 34 | Joined: 06/12
Posted: 06/25/12
07:10 PM

I just figured out that the O2 sensors are in the catalytic converter, I don't have a pipe past it so that could be causing an issue with the back O2 sensor.  

idabomb00 idabomb00
New User | Posts: 34 | Joined: 06/12
Posted: 06/25/12
07:18 PM

No shop dude, just working in my front yard out in the sun.  

waynep71222 waynep71222
Guru | Posts: 825 | Joined: 03/12
Posted: 06/25/12
08:48 PM

i know the feeling...

and its really hot in the sun these days...

94 models... have sensors either in the exhaust manifolds or in the head pipes.. NOT after the cats...

only 96 and newer models have them after the cats..  unless you have a later exhaust on it.. or modifications..

log in check private messages for a link to where the oxygen sensors are hiding...  

idabomb00 idabomb00
New User | Posts: 34 | Joined: 06/12
Posted: 06/25/12
09:50 PM

Okay thanks... will do  

idabomb00 idabomb00
New User | Posts: 34 | Joined: 06/12
Posted: 07/11/12
12:14 AM

Finally got the pipe on, It didn't have enough back pressure, really appreciate the help!  

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