Cold Start Rough Idle Wants To DIE Stall Out

diyer2 · July 16, 2018

My 2012 5.3 with a little over 63 K miles was having a hard time starting after sitting over night.

The temps here in the mountains have been around 50- 55 degrees Fahrenheit in the mornings.

If I didn't keep it running with the gas pedal it would die.

After 10 to 20 seconds it would run right.

Spark plugs were replaced recently.

Air filter is a K&N, recently serviced.

Battery is good.

I use Top Tier Shell gas.

I started with the easy fix, a bottle of Chevron Techron in 3/4 of a tank of gas.

That's how much gas was in the tank when I decided to try fuel cleaner.

Ran that tank to 1/4 of a tank.

Didn't fix it.

Filled it up ( mid grade 87 octane here) and added a can of Sea Foam.

Went on a fishing trip and towed the boat a hundred miles round trip.

Fixed it.

Still have 3/4 of a tank of Sea Foam gas in the tank to run through it.

My guess is the problem started due the driving I do know.

It's 6 miles to town and the mountain roads limit your speed to 40 mph tops so it doesn't get used hard.

I would think pulling the hills on a round trip to town would work it enough.

Maybe I got some bad gas.

So far it has started like normal.

sefiroxx · July 16, 2018

3 ideas:
1) water temp sensor that informs the computer of the car is warm or not. It may have failed (or wiring) into a state of always warm
2) clean throttle body/butterfly. It could be gummed up and sticking nothing allowing the control to open the extra bit needed for warm up
3) throttle actuator (control motor and tps sensor combine).

diyer2 · July 16, 2018

22 minutes ago, sefiroxx said:

3 ideas:
1) water temp sensor that informs the computer of the car is warm or not. It may have failed (or wiring) into a state of always warm
2) clean throttle body/butterfly. It could be gummed up and sticking nothing allowing the control to open the extra bit needed for warm up
3) throttle actuator (control motor and tps sensor combine).

Thanks for the suggestions.

So far it has started like normal after the Sea Foam treatment.