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Running Lean when cold - stumbles/dies

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Hi All,

I have been trying to figure out why my T2 converted GLH runs lean when cold. Here is my configuration:

1985 Omni GLH converted to GLHS T2
Ported E1 head
+20 injectors
88 Roller Cam

When I start the car cold, it will start and run for about 10 seconds or so and then go way lean (18:1) and most of the time stumbles and then dies. The only way I can keep it running is my keeping the rpms above 1500 until the car warms up. Once the car warms up to a certain point, the car will idle fine. AFRs are in the normal 14:7 range. Recently I had to replace my injectors for an unrelated issue and ever since I did that, I have this cold start issue. The new injectors I put in are MP +20s and they were flow tested to my understanding. Here are a few things I have tried thus far:

1. Tried a few different known good LMs and they all experience the same problem.
2. Confirmed with a MityVac that I don't have any vacuum leaks. I am currently running a vacuum block.
3. Tried different known good MAP sensors but they experience the same problem.
4. Computer is not throwing any codes.
5. With a Digital Volt meter I back probed the coolant sensor at the LM to read the voltage and it seems within spec.
6. Swapped power modules with a known good one and have the same behavior.

Would a bad injector cause this issue even though it idles fine once warmed up? Any thoughts are much appreciated.
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On a cold engine you are running on a fixed program, the vehicle will not enter closed loop operation until the proper time/temperature have been reached, when not in closed loop the engine controller ignores the O2 sensor.
You are in closed loop operation when your wideband is reading 14.7/1. Closed loop operation only takes place at idle and no load cruise.
Did you install an engine controller that is compatible with the newer electronics, 84/85 used a different distributor than 86 - up, the 84/85 LM cannot be used with an 86 - up distributor and vise-versa.
b)You upgraded to the underhood Map Sensor and are not using the LM mounted Map Sensor.
c)The main controller ground is properly connected to the fuel rail and has < 5 ohms continuity to ground.
Schematic Rectangle Slope Font Parallel

2)Fuel Pressure (on a cold engine)
Static (KOEO) 53-57 PSI.
b)Engine Running - With the engine running you are looking at total fuel pressure across the tip of the injector, total fuel pressure is a combination of push (rail pressure) and pull (engine vacuum). Rail pressure will drop by 1 PSI from static rail pressure for every 2" HG applied to the FPR. Engine running rail pressure + engine vacuum will always = static pressure.
IE: Static = 55 PSI Static, Engine Running with 18" HG = Rail Pressure of 46 PSI. 46 PSI + 18" HG (9 PSI) = 55 PSI total.
3)Map Sensor Calibration
Initial key on, the engine controller reads actual Barometric Pressure.
The engine controller then uses this number to compare to actual engine vacuum/pressure, if Baro is off, everything is off.
Is the reading correct for your area with the present weather conditions?
b)Engine Running - Map voltage will = vacuum/pressure being applied.
Is the voltage reading = to the vacuum/pressure being applied?
c)Be sure that there is no moisture in the vacuum line running to the Map Sensor.
d)Be sure that vacuum is not being trapped inline between the Baro Solenoid and Map Sensor when the engine is shut off.
4)AIS Operation
Base Idle is set correctly.
b)Throttle plate and/or AIS pintle are not carboned?
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Just a thought, but have you converted your T1 ais/tps to T2? I had this problem before when i couldn't use my ais in my 84 daytona with a newer style ais in my 2.5T1. When i ended up converting the wiring over to SMEC i could finally use the ais again and the problem went away...might be the same issue.
Thanks guys for your reply. I will start with replying to NAJ:

1a - Yes. I am running a GLHS MP Stage 2 computer and 86 and up distrubutor
1b - No. I am using the LM mounted MAP sensor. Just as it came on a GLHS.
1c - I will check this tonight

2a - Confirmed static fuel pressure of 54psi
2b - With the engine running at 20" HG, my fuel pressure is 44psi

3 - I will look into this tonight
4 - I will also look at this tonight.

With regards to the AIS/TPS question, Yes I have converted them to T2. But I will confirm voltages and such for the TPS to be sure it is ok.
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