Rough engine idle only at cold start up and smoothes out quickly?

Question

I have a 2002 GMC Envoy with 108k miles and have new air filter, fuel pressure regulator, spark plugs, fuel filter, and just did 3 step fuel injection/throttle body/gas treatment service.

It idled longer and rougher before I replaced pressure regulator, but I'm running out of options. Also, the "check engine" light does not come on.

So would changing my vacuum hoses help/fix this? What could this be?

Any help would be appreciated.

Thanks

Ariel

Answer 1

have a ODBII code reader hooked to it and see what it says. not all engine errors make the check engine lite come on. most likely there ia a damaged vacuum hose somewhere

Answer 2

you probably did not say that the vehicle is carbureted or gas injected. If it has a carburetor, this may be the issue. once you've an automatic choke, examine to work out that it does not stay closed for too lengthy. I had a simular problem with my previous GMC p.c..-up. even as the motor is chilly, it truly is going to commence appropriate up, yet will lump at idle and sense demanding because the choke aspects a too wealthy a mizture and overloads the engine to the point the position it needs to run demanding, very almost to the point of stalling. once the motorized vehicle choke starts to go back open it smooths out. examine the choke. i'm not declaring that is the issue, in spite of the undeniable fact that it sounds so very like the issue i grow to be having with my p.c..-up.

Answer 3

The fuel pump could be letting fuel bleed back into the tank. Try turning the key on and off, 3 or 4 times before you start it. There are several other possibilities, EGR valve, IAC motor, etc... A scanner will narrow the possibilities quickly, and most likely pinpoint the problem.

Answer 4

go to www.automotivehelper.com and click on the forums sections. these guys are great and know their stuff. it may take some time for them to get back to you but more then likely they will be a big help.