SOURCE: 1998 gmc sonoma push button 4x4 busting diaphram vacuum actuator
On top of the transfer case is a vacuum switch with 3 vacuum lines connected to it. This switch controls when vacuum is applied to the vacuum actuator. This switch can fail partly and allow fluid from the transfer case to be sucked up into the vacuum lines and anything connected to them as well. When you replaced the actuator before, did you notice any oily fluid inside of it?
SOURCE: I need to see the "how to's" in replacing the one way check valves on my 2001 gmc sonoma 4.3
On the 2001 gmc jimmy 4.3L v6 engine there are two air pump check valves: there's a pipe (about 1" diameter) that comes off each of the exhaust manifolds. the check valves are screwed onto those pipes. then a rubber hose (about 1.25" outside diameter) is clamped to the front of each check valve and connects to the air pump, which is hidden behind the vehicles grille in front of the radiator. typically, if you need to replace these (the life expectancy is about 3-4 years), it starts a chain of events that might be as follows: during the wintertime, water from the exhaust leaks through the worn out one-way check valves, and ends up in the air pump. the water freezes, and the ice jams the air pump, which may or may not ruin the air pump, but which usually blows the air pump fuse, which is impossible to find if you're rummaging around the passenger compartment fuse box or the under-hood fuse and relay box. it ain't there! so if you're looking under the hood leaning up against the front bumper, slide to your left around the passenger side headlight. now you should be looking at the battery, leaning up against the passenger side fender. look down between the battery and the fender. you have to push a few things out of the way, but there you will find a green 30 amp blade fuse (about 1" x 1" fuse--and $2.99 at autozone). this blown fuse should have triggered the check engine light and a DTC (diagnostic trouble code) of p0410 (secondary air injection system). for that vehicle there is a TSB (technical service bulletin) put out by gm (bulletin # 04-06-04-015; march 2004). if you want to print out some literature about all that i've mentioned just surf on over to http://www.obd-codes.com/p0410 for more links and documentation. my credentials: self-proclaimed auto mechanic for 26 years (sorry, no ase certification yet [but still trying to find time to study for the tests]) and college dropout (after 3 years of electrical engineering)--so, in other words, don't believe a word i say; just go to that website and get it straight from the horse's...
Good luck and hope this helps. I know you have a Sonoma but we have the same platform. I am thinking of buying a set of headers without the Air injection system and having the jimmy dyno tuned again to eliminate the service engine light and recalibrate the ECM to eliminate the air injection pump.
SOURCE: won't idle
Try cleaning the throttle plate with carb cleaner and a toothbrush, be sure to clean the edges.
SOURCE: i need a vacuum diagram for an 89 gmc jimmy 4.3
helminc.com Complete service manual Not Cheap May try library or repair shop with a subscription to a tech hot line. They may let you see what they can call up on line. How about finding someone with the same veh and spend an hour fixing your issues the way they are on a good driving vehicle.
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