have a 2005 1500 5.7 180k Currently -28C outside.

Truck has been giving me intermittent cold starting issues, when she's running all is well. When it sits overnight in the blistering cold the morning start is rough. At times 8-10 attempts. Truck turns over fine, battery is fine, i can hear the fuel pump kicking in. She stumbles and chokes out....almost like its flooded. When i do get her to start and rev it up a few times to clear out the fuel she idles nicely at times rough because of the bad O2.

At this point i can turn it on and off even while sitting for 8 or more hours. When i park it overnight she intermittently puts me through the cycle again.

I originally thought it was the fuel pump (fuel pressure regulator). I could hear the pump kicking in but maybe not pumping out enough pressure. So i ordered one online for more than 1/2 the price (114.00) of what the part stores were asking which was 269.00. So that's on the way.

While sitting in the truck with the old computer and obd scanner i noticed that Bank 2 Sensor 2 was reading a range of 0.000 to 0.155 at idle and rev'd rpms. The Long Term Fuel Trim Banks 1 and 2 are reading in the double digits (11.71 and 14.84) while rev'd up.

When i plug it in over night....she starts no problem just a bit rough until it warms up.

Question is would a bad O2 sensor cause the engine to get too much gas as an accumulation through out my daily commute? After sitting the fuel accumulates flooding out the engine resulting in a hard start? I thought this doesn't happen to FI vehicles??

I understand that the O2's are not read by the computer until they are in a closed loop so it shouldn't affect starting. Could it be a Vacuum leak?

 

I've highlighted the issue for you....

As long as you don't have a check engine light lit up showing a DTC for a bad O2 sensor you're problem is that it's simply too effing cold....

Get a block warmer installed plug it in an hour or so before you've got to get the truck started, and put some extreme cold weather additive into your coolant.... (make sure the additive is HOAT coolant compatible)


Easiest way to setup the block heater to turn on, is a simple outdoor grade outlet timer set to turn on 30-60 minutes before you've gotta get in and go each morning.

The colder it is the more fuel will get dumped in, There's no way around that... but the issue is that you're coolant is damn near frozen, and your oil is extremely thicker than usual, so it provides additional resistance to your engine's operation.

 

LOL...thanks. Your point is still valid, because when i do plug in she fires right up. However in previous years i have never had to plug in.

I did have a few DTC codes, P0157 and P0158. All of which point me to B2/S2.

 

replace that O2 sensor and it will help the idle problem and your fuel economy will likely increase a bit again, that won't give you a problem on first start-ups b/c the sensor hasn't had a chance to warm up enough for the PCM to read from it, which means it is only using the MAP and IAT to adjust fuel injection, and when it's cold the IAT freaks out and the MAP is seeing air that is much more "dense" so it dumps fuel in and you get a rougher than usual idle too.. and once the o2 sensor warms up it's giving bad readings which hurts your idle too.

But the real issue is the coolant that is turning to slush and making the water pump work extra hard and not allowing proper flow... as coolant gets older and goes through more and more heat cycles it begins to break down and it's freezing point will change (increase), which means it will freeze at a higher temperature than it would if brand new.

Plug the block heater in and see how it changes... Replace the O2 sensor and your truck will idle better once the sensor warms up too.

 

I guess it would be safe to assume that if i had a problem with the MAP or IAC i would get some sort of DTC error correct?

 

replace coolant, extra low temp if available.
start using "Dry Gas" dampness in fuel.
look into a block heater.

gasoline is NOT flammable under -20C... look it up. YOU need to help it. see above.

all sensors on the engine will flag a problem if defective. its there job. OBD11.

my Opinion.

 

How do you know that the fuel pressure is low, have you tested it? A fuel pressure tester is a lot cheaper than a fuel pump that you may not need.

 

It was just an assumption. I'm hoping to locate the fuel rail today and see if i've got fuel coming out of the valve/plug....otherwise a pressure gauge is next on my list.

 

Yes immediately you'd get a DTC....

Also if you did not have fuel pressure you would get a DTC, actually you would likely get a few.... including extreme lean situations.

and @ chuck_hammer.... show me proof of that... I know the gasoline tends to not want to vaporize as easily in colder temperatures, but I've never heard that it is "not flammable"...

 

I do not remember where.. years ago..

retired auto mechanic (43 years)
gas does not vaporize under -20C... NO Vapor.. No fire.

if the metal in the intake/(aka air) is at -20C.. and in a cylinder.. a spark will not fire off the gas.. as NO Vapor..

look up WHY.. when they were building the oil pipe line in Alaska.. the gas engines were run all winter. and many still do today.. look it up.