Cold start issues

[Thetonk]

I'm having a problem. I have an '06 trailblazer with the 5.3 engine. When it's cold outside Freezing and below. The engine will start. Run for three seconds. And shutdown. Pass lock light stays solid. The engine won't crank for about a minute. And it'll do the same thing. If it's about 40 or above. No problems. Any ideas?

[MikeCStig]

Cold starts can be a problem in any vehicle. You're asking your engine to fire up under conditions that it doesn't like and if it's ridiculously cold it may disobey. Here are some things that have worked for me.
-Turn the ignition on (don't start the engine) wait 5 seconds for the fuel pump to build pressure, then shut it all off. Repeat this process one more time, then do it a third time, but this time after you allow the fuel pump to prime, start the engine
-When the engine starts, give it a little throttle, and keep giving it throttle until you're confident that it will run on its own, don't drive until the engine is fully warmed up.
-When it's cold, run premium fuel or use an octane booster. I'm running premium right now and my car doesn't even require it, but I live in Maine and it's f**king cold up here!

So there are some ideas and I hope one of them helps, good luck.

[Schurkey]

I'd suggest investigating the PassLock system.

Originally Posted by MikeCStig

Turn the ignition on (don't start the engine) wait 5 seconds for the fuel pump to build pressure, then shut it all off. Repeat this process one more time, then do it a third time, but this time after you allow the fuel pump to prime, start the engine

GM runs the fuel pump for two seconds to pressurize the fuel system when the key is turned from "Off" to "On". If this two-second "head start" for the fuel pump isn't sufficient, it indicates a fault in the fuel pump wiring, the fuel pump, or the fuel system check valve that retains pressure in the fuel system after the pump has shut off.

Originally Posted by MikeCStig

When the engine starts, give it a little throttle, and keep giving it throttle until you're confident that it will run on its own, don't drive until the engine is fully warmed up.

Indicates a fault in the idle-speed control system--the Idle Air Control valve or the wiring to it. There is no need to "warm up" an engine before driving, or to stabilize the idle with the gas pedal. Even ancient carburetors had a fast-idle cam.

Originally Posted by MikeCStig

When it's cold, run premium fuel or use an octane booster. I'm running premium right now and my car doesn't even require it, but I live in Maine and it's f**king cold up here!

Completely un-needed. A cold engine is unlikely to detonate, and that would be the reason to increase the octane rating.

A carbureted or throttle-body injected engine would appreciate gasoline blended for low temperature vaporization. This is done by the refinery for gasoline sold in any climate needing the cold-weather gasoline. If your vehicle doesn't run right in very cold weather--and you've still got gasoline in the tank from the summer before--it may run poorly when cold.

[Thetonk]

Well it warmed up enough for me to get over to my buddy's shop to scan the computer. P0601 code which indicates an internal fault in the Pcm. I've recently found 7 other threads with the exact same symptoms stating people replaced their pcm. Problem solved. So. Pcm enroute

[paulfromoh]

My 03 avalanche kept throwing a PCM and Mass air flow sensor code. Because the whole thing is run by a computer, it would cause the engine to run too rich and it would run like crap once the code was on.

My solution was to erase the code and it would run fine for a few days. I ended up cleaning the mass flow and replacing the pcm but neither worked. The final solution was just a basic tune up with new plugs, wires etc.

[Lms2015]

I am having the same issue. When it's cold outside my trailblazer will fire up for about 5 to 10 seconds and completely shut off. Even if you rev the engine up it still stalls. Strange thing is, if the temperature is above freezing but below 50 degrees you can heat the key up, start it up and it will stay running as long as the inside of the car stays warm it will stay running - if the inside gets cold it shuts off again. If it's above 50 degrees outside it starts and runs with no problem. It's been in the shop for 2 weeks and they still can't figure it out. They are leaning towards replacing the computer but unsure if that's really it. Mine is also an 06. New battery, alternator, ignition switch and key switch. Any ideas??

[Schurkey]

Originally Posted by Lms2015

I am having the same issue. When it's cold outside my trailblazer will fire up for about 5 to 10 seconds and completely shut off. Even if you rev the engine up it still stalls. Strange thing is, if the temperature is above freezing but below 50 degrees you can heat the key up, start it up and it will stay running as long as the inside of the car stays warm it will stay running - if the inside gets cold it shuts off again. If it's above 50 degrees outside it starts and runs with no problem. It's been in the shop for 2 weeks and they still can't figure it out. They are leaning towards replacing the computer but unsure if that's really it. Mine is also an 06. New battery, alternator, ignition switch and key switch. Any ideas??

Replace the key???

Replace the lock cylinder???

[Thetonk]

Mine was the pcm