Hey All!

Proud owner of a 2005 scion xb here! Mileage only at 125k. Been a rough couple of months with the Box. Been doing a lot of 100k maintenance. It had been having issues with air/gas mixing with numerous CEL codes. MAF was replaced with one from Toyota Dealership. I installed both new 02 sensors up/downstream. All CEL lights have been clear for better then a month. Drives fine, no stalling, no misfires, nothing to note that is unusual. Except the first start of the day. It usually stalls and dies quickly unless I tap the gas a little. If its warmer, say 40 degrees or so it starts but idles rough for a minute or so unless i give it a rev or 2. When it is cold, it will not start and dies multiple times, once i give it gas and rev it a bit all is well.

Weird thing is, its only the first time i start it daily. Once it runs it is fine until the next day.

Where do I start? I've read so much and watched so many videos. I'd like to solve it myself to save money as i have already put to much into it over the past year.

Fuel filter?
Fuel pump?
Fuel pressure regulator?
IAC valve?

Thoughts?

Thanks in advance!
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What do your spark plugs look like?

 

According to my records, they are 2 years old. They were replaced by my trusted shop. I will take a look at them today to make sure though.

 

Have you checked the fuel system for leaks, and pressure? Had a problem like this on my 2005 and it had a slow leak in the fuel system.
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I think the original plugs were just standard plugs, nothing like iridium, and they do wear out (erode) pretty quickly and can give you the kind of symptoms you noted. My notes say we replaced than with iridium at 55,000 miles and the original plugs were eroded with gaps of .040"-.050". Supposed to be .028"-.031". The ground side of the iridiums eroded a bit at 105K, just re-gapped.
Probably need to check them again now it's at 165K.
Put them on the list of things to check at 170K

 

I looked back in my car repair notes and the spark plugs were changed 23,000 miles ago with platinum-iridium ones. I am still going to take a look at them this weekend.

It makes me a bit nervous to mess with fuel related things, how do you even check fuel pressure?

 

If I were looking for anything fuel-related, I'd check for leaks first. Based off the fact that it runs fine on a warm start, I wouldn't say the problem lies with the injectors or fuel rail, but I'd follow the fuel lines from the rail down under the car (you'll have to jack up the car), and take a look at the fuel filter. The reason that a fuel leak makes sense to me is that a "cold start" is the issue not because the actual engine temp, but because on a more recent start, the fuel has still been left pressurized from when it was started earlier, but as you mentioned, fuel pressure is lost overnight....

If it weren't the fuel filter, I'd check the fuel pump. It's worth replacing anyway considering the age, especially if it is original. It might just be weak at this point and needs a moment to get the fuel where it needs to go. Replacing the fuel pump isn't so difficult anyway on these cars.

I wouldn't think IAC simply because it wouldn't make sense for the problem to resolve itself as you continued to drive.

Your spark plugs are also fine, anything iridium can last a good 100k miles without issue.

It's hard to say what the problem actually is without being able to take a look at anything, but I'd inspect all throughout where the fuel runs and honestly just replace the fuel pump anyway since it seems about time to do it anyway.