cold starting problem
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cold starting problem
Folks, I need some help/
2001 SCrew 5.4 135K miles. Very hard to start when cold, below 45 degrees. Once running is is perfect. Idles smoothly and runs and pull like new. Today its 30 and now it won't start at all. squirting starter fluid hasn't made any difference. IAC is about 20k old. Cleaned MAF no joy.
Help!
TC
2001 SCrew 5.4 135K miles. Very hard to start when cold, below 45 degrees. Once running is is perfect. Idles smoothly and runs and pull like new. Today its 30 and now it won't start at all. squirting starter fluid hasn't made any difference. IAC is about 20k old. Cleaned MAF no joy.
Help!
TC
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
Best I can do is explain how the system "knows" and handles cold starts.
You have to run down the reason for failure.
When you turn the ignition to 'run' (before cranking), the PCM looks at the coolant temp sensor value to determine it is a cold start.
This opens the IAC, richens the fuel and advances the ignition timing.
Once the motor is running the idle is supposed to be high because the IAC is open more and the fuel is rich.
I would start by testing the coolant sensor for resistance when cold to see if it is within limits and sends the right resistance value to the PCM.
Next the fuel pressure to see it is in the 35 +/- range.
Next for any air leaks in the intake system.
If nothing is found with these items, look at the possibility a crank sensor, cam sensor or connector being a possible cause when cold only.
Otherwise a good idle and running after the motor starts and warms does not indicate much else faulty but those items directly involved with cold start.
Good luck.
You have to run down the reason for failure.
When you turn the ignition to 'run' (before cranking), the PCM looks at the coolant temp sensor value to determine it is a cold start.
This opens the IAC, richens the fuel and advances the ignition timing.
Once the motor is running the idle is supposed to be high because the IAC is open more and the fuel is rich.
I would start by testing the coolant sensor for resistance when cold to see if it is within limits and sends the right resistance value to the PCM.
Next the fuel pressure to see it is in the 35 +/- range.
Next for any air leaks in the intake system.
If nothing is found with these items, look at the possibility a crank sensor, cam sensor or connector being a possible cause when cold only.
Otherwise a good idle and running after the motor starts and warms does not indicate much else faulty but those items directly involved with cold start.
Good luck.
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