'01 Sierra rough start

[OldGoalie915]

I have a 2001 GMC Sierra 5.3. It has been an incredible truck and an absolute dream to drive. Other than a replaced tranny and water pump nothing mJor at all has gone on.

The problem I am having is that it is incredibly rough idling in cold weather and by that I mean anything below about 50f. It gets to the point where I have to baby it just to get it going enough to warm up.

I had taken it to the shop last year and they said it was the belt and replaced that. They also replaced the waterpump which had cracked and was under warranty. It started to happen again so I took it to the shop yesterday and they changed the fuel filter, plugs and wires and fuel sensor. Well lo and behold it happened again this morning.

Does anyone have any ideas? I am at my wits, and wallets, end.

 

Thanks in advance.

[dgrinnell]

Does it smooth out when it warms up? If so sounds like the intake manifold gasket. My old 01 had rough cold idle then when it warmed up it ran great.

[MikeInCtown]

Before they replaced the fuel filter did they check the fuel pressure? (what is the pressure?)

 

I can't remember when the changeover happened. Do you have the 8 coils or a distributor? Assuming 8 coils, it's hard to believe that all would have a weak spark., and history has shown me you have spark problems as coils get hotter.So you are left with air and fuel delivery. Air delivery would be an all the time occurance. Fuel delivery problems can seem worse when an engine is cold and or wet.

 

Just my two cents, but i wouldn't go further until you know what the fuel pressure at the rails is.

[OldGoalie915]

It does smooth out once it warms up.

[efritz]

Very likely an intake manifold gasket. You can test by spraying a little bit of starting fluid around where each intake port seals on the head when its cold. If the idle speed changes when you spray, they're bad. Is it accompanied by a check engine light with bank 1 or 2 lean codes?

[govener71]

It could be a stick Idle Air Control Valve. If there is carbon build up on the throttle body or something gumming up the works it might loosen up as it gets warmer, it is a pretty cheap part and just two torx/star bolts to replace it. I know you dont want to just throw new parts at it, but I feel like if it was the intake manifold it would be throwing a code if it was running that poorly.

 

http://www.1aauto.com/1A/IdleAirControlValve/GMC/Sierra1500/1AISC00020/615370-2001?utm_campaign=gb_csv_br&utm_content=ISC&gclid=CLSk0-iYrLsCFdE-Mgod3mcAJw

[Bad Bowtie2]

Any updates??

[OldGoalie915]

Mechanic says it is either the intake manifold or the gasket. How huge of a job us it to replace the gasket?

[OldGoalie915]

It was throw I g check engine light when I brought it in.

[govener71]

at a dealer it would be around 250 I believe, at least when mine was done. I would suspect a local guy in the 200 range or slightly under. Not to terrible of a job if I remember right.