So, Im goin to pick up my first Blazer this Friday off of a freind, its a 95' 4-door, 4x4, black on black, 160k, in really good shape, the thing is it idles high like thers a vacuum leak, and has lost some, but not all of the power assist from the brakes, this is the only problem with the truck and it is still perfectly drivable, but any ideas on what this may be? Either way its well worth th $500 im giving him for it.

 

Since a vacuum leak can cause both of these issues, I would first have a look at the vacuum booster. If with the engine running, after pulling the vacuum line & check valve off of the front of the booster, you do not hear a rush of air entering the booster, the booster itself is bad. Just be sure to put your hand over the end of the check valve to keep the engine from racing.

Actually, that is the other check. With the vacuum line disconnected at the booster and your hand over it, does the engine return to normal idle speed?

 

Did both of those and the booster checked out ok, thanks. I noticed there were some vacuum lines that were dry rotted and cracked, so I replaced those, and it ran better but I know I just need to go ahead and do all of them.
The problem I have lies in the IACV I think. I removed it and cleaned all the carbon off, then after looking at it kinda figured out how it worked and also figured out that it could be adjusted by pulling back the spring and turning the rod. I did this a few times untill I got the desired Idle speed. Drove the truck and it drove great, no more "running away" when I let off the gas, brakes worked as they should, ect. The only problem now is sometimes when its cold you have to give it like 1/8 throttle to start, then it idles like a cammed out monster small block till its warm, then its perfect. Soo, its 65 bucks for a new valve, but my buddys got a junk blazer with the cpi maybe ill try that one to see if it works.

 

Sounds like the IAC valve is gone just as you have surmised.

 

Well, replaced the iacv, to no avail. The truck still has an intermittent rough idle and loss of vacuum. WTF. Really gettin on my nerves. Sometimes it will be perfect, good vacuum and great idle, you can barely tell its running, but more often now than not it runs like hell has no very little vacuum wich makes the brakes very stiff. Now I can hear an audible whistling, like something is leaking (vacuum)but cant pinpoint it exactly. It sounds like its coming from the front of the IM maybe beneath the TB. But I cant tell, and it was getting dark and very cold. Just on a hunch I looked underneath the truck and sure enough the cat was starting to glow, so I shut it off. Is there anything in that area that could cause this weird problem? I know if I knew what codes if any that it was throwing, it would help, but Im still workin on that, cause its obd 1.5.

 

Also, the guy I got it off of, said sometimes it would run rough and he would have the EGR cleaned, and it would fix it. He knows nothing about cars, but could this be the prob?

 

Alright well after doing some searching I found some people with EGR problems that have my symptoms, so Ill try to clean that this weekend.