after failing myself and all non-dealer shops I trust failing I took it to the dealer Monday afternoon. After sitting all night to chill, they start it this morning and it runs perfect. I said keep it one more day. Temp supposed to be down a little tomorrow. We will see

 

swap in a maf out of the parts yard.

 

MAF, IAT and IAC all new

 

got truck back from dealer. $72 bill for new fuel pump and cleaning the TB. It does seem to run a little better, but the cold weather rough idle is still there. Crap

 

I'll hazzard a rough guess. Look for the vacuum leak. It may be anywhere. "even the pcv system."

 

have you tryed snugging down the intake manifold bolts ? or the ones at the throttle body?

my 01 makes a slight vac leak sound till it warms up on colder days but when warm it's ok
I'm figureing that's what mine needs - it can be a little ruff & chunky on cold mornings too

I'd forgotten about it untill it got colder out again - when warm I have no issues with it

 

it's been in the 70's there in the "southern state of Tennessee"

 

Try isopropyl in the gas tank. Look for a crack in your intake by removing it and searching for damage. Even around the Maf or hose clamp, even inside the air box all the way back thru the entry point. U are accomplishing something this way, removing 1 thing at a time from your list. In the end pull the intake manifold and redo, just crossing it off your list of things to do today. Even a crappy connection at the EC"U for the fuel injectors circuits. Pull the ECU and inspect it for burn/corrosion in/on it. Internal circuit damage. Just croos em off the list of TTDT. Never a quiet dull afternoon in the future. LOL

 

just noticed something. When you start the truck there is about 15 to 30 seconds or normal idle before the roughness starts. But if you shut the truck off while it is idling rough and start it right back you get the same 15-30 seconds of smooth idle before the roughness starts. it does this when the truck is first started or if the truck has been running long enough that the temp gauge is showing normal operating temperature.

also when it is idling rough, the exhaust really stinks, not sure if it is a rich smell or just a funk, but it stinks

the truck still logs lean bank one and two codes

 

When you first start it the PCM thinks everything is normal. Then after the sensors start reporting it adjusts it's self because of the lean codes. That explaines the 15 to 20 seconds of bliss.

Remember that the lean codes make the truck run richer as the PCM tries to compensate for the air leak, this is very bad for the cats.

Go over EVERY vac line to look for cracks or breaks. Check the vac box by the battery for cracks and good connections. Then examine the complete PCV system.

After that if no issues are found then start the rip and tear that Papa Tiger suggested.

You have a major vac leak somewhere.

Good luck.

 

I recently got an error code on my 2001 that showed a vac leak as a possibility. I was amazed at how many little rubber vac tubes there were. I replaced all that could be accessed easily and found that most just crumbled when I rubbed them between my fingers. And it ran fine! I think i recall three different tube sizes...

 

With that many miles, have you replaced the O2 sensors?

 

no but I have wondered about them. If they were failing and reading lean, the computer would make the mixture too rich causing the rough idle and smelly exhaust.

What I don't understand is how the failure could be triggered by cold weather.

any ideas?

 

bought a small propane tank and fitting today. Going to try to find a leak. If it goes boom, I guess it wont matter where the leak was. Perhaps the best solution would be to use the tank the way they did at the end of the first Jaws movie.

 

For that you're going to need a bigger boat....