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Hard starting...autoxray results

D

DPellarin

Guest
Hello,
I have been trying to fix a starting problem that has been occuring on my '92 for a while now. It starts right up in the morning, but after it is driven and parked for about an hour, it cranks over for about 4 seconds before starting. I have verified that the fuel pressure holds, the injectors do not leak, the pressure regulator does not leak, and the fuel pump is not alowing fuel to bleed back. I have also replaced the coil because the resistance was a little low on the original, but the problem still exists. It is getting an injector pulse while cranking and it is also getting spark.

I did a scan with an autoxray and was hoping that someone could advise me on anything that doesn't seem normal. The first values were taken with the key in the "on" position, but without the motor running. The second values were taken as soon as the motor started after taking awhile to start. Both scans were done after the car had been sitting about an hour after being driven.

Vehicle Data PROM ID 3881, 3881
Coolant Temp 182.7°F, 183.5
Throttle Sensor 0.6 Volts, 0.62
Throttle Angle 0%, 0
Engine RPM 25, 650
Vehicle Speed 0 MPH, 0
Oxygen SensorR 448 mVolts, 448
Oxygen SensorL 453, 453
Block LearnR 128, 120
Block LearnL 128, 120
BLK LRN Cell 0, 16
Integrator R&L 128, 128
Idle Air Mtr Pos 85 steps, 8
Desired Idle 3187 RPM, 637
MAP Sensor 4.88 Volts, 1.35
Manifold Air Tmp 147.4°F, 133
EGR Duty Cycle 0.0%, 0.0
CCP Duty Cycle 0.0%, 0.0
Battery Voltage 11.9 Volts, 13.9
Learned Idle Pos 10 steps, 10
Spark Advance 2°, 24
Knock Retard 0°, 0
Engine Run Time 0 seconds, 2
Battery Voltage High : No, No
Shift Light Off
TCC Status Not Locked
Park/Neutral Not Detected
Fan Number 1&2 Off
A/C Clutch Disabled
CCP Purge Off
Learn Control Disabled
Loop Status Open


The part I am not sure on is the desired idle. It is at 3187RPM before the motor is started and while cranking, but when it starts it goes to the normal 650RPM. Also, it is reporting 25RPM when the motor isn't even running. When the car cranks for awhile, after it starts it smells rich and this is verified by the BLM showing 120 after it starts, and then it climbing back up to 126-128.

What do you think?

Thanks,
Domenic
 
T

tvalley641

Guest
Both scans were done after the car had been sitting about an hour after being driven.

Vehicle Data PROM ID 3881, 3881
Coolant Temp 182.7°F, 183.5


182.7 degrees F after 1 hour!! Whew. My idea, without knowing what half that data means, is to let her cool way down... to about same temp as when "it starts right up." Then compare the figs. A dummy might be able to "see" something then. Worth a try.

Ted
 
D

DPellarin

Guest
I did another scan this morning when the car was cold and starts quickly. The only changes where in:
Coolant temp: 58.5
Manifold temp: 50.7
Idle air: 134 steps
Spark advance: 6 degrees

This was taken with the key on, but without the motor running. I am thinking that maybe the idle air control valve is not opening enough on the hot starts, but I have cleaned it and reset it. Any ideas?

Thanks,
Domenic
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
I think your problem is here:

Idle Air Mtr Pos 85 steps, 8


I think your Idle Air motor is sticking and eventhough the system is trying to calibrate it, it is staying hooked to where the motor does not get appropriate air mixture for start up.

Take it out and clean it and the throttle body and reassemble. Go through the recommended steps for resetting the idle air mode. That should fix the problem :)
 
D

DPellarin

Guest
Thanks for the advice. I have taken the IAC out and cleaned it before, but noticed no change. Maybe I need to replace the valve with a new one. I have also noticed IAC counts down to 0 when the motor is running. I am not sure if this is normal.
 

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