Since I have owned my Blazer, roughly 6 months, I've had hell with the 4 wheel drive not engaging. I was investigating the vacuum lines on a friends advice when I found a few under the hood on the drivers side that were in rough shape. One had engine vacuum, which led to a small plastic junction that split into two lines. I changed these simply because they broke apart when I touched them. This did nothing to fix my 4 wheel drive problem. The next day, the car decided to drop RPMs when I was driving, falling to roughly 1k before returning to normal. Every so often, the RPMs will drop further and it will stall on the road.

I would assume changing the lines up front has made others blow out as pressure shifts to older hoses, but I have no idea where to look for these. The car is running no codes currently and works nearly fine most of the time, it is only every 20 minutes or so that it dies.

Thoughts?

 

If some of your vacuum lines were bad, then they should be replaced. I have a link to a thread I made up in which I documented all of the lines I replaced and where they go on my 99 4wd with the 4-button transfer case. You might look at that to see if you missed any that still need to be replaced.

 

Thanks, I'll check that out. I just found a hose running from the intake manifold that wasn't connected to anything, managed to figure out that it went to the secondary air system under the radiator. Not sure if that would cause the problem, I dont know why it was disconnected. I''ll probably check all of the other lines to be sure.

 

I can't see a vacuum leak dropping the RPMS then returning back to normal - with no codes present I would also check fuel pressures - There is no set readings for engine running but you might leave gauge hooked up and position it where you can see it while driving to see if there is a drop in pressure as RPMS change.

 

I checked all of the things i mentioned previously, and found nothong wrong. Thankfully a friend found the alternator to be dying, every so often it would slip and fail or size or something. Changed it and the belt, now I'm running fine.

On a side note, this is my first serpentine belt changed. I'm certain it is well aligned and the automatic tensioner is very strong still, but it squeaks evvvvry so often. I figure its the new belt - too smooth or something? I dunno, throw me thoughts if you'd like.

 

On the serpentine belt issue, did the noise appear before or after the belt was replaced? If after, I would suspect the belt tensioner pulley. The new belt will be shorter and will cause more tension on that pulley. They are prone to do this. Did you have alot of trouble putting that new belt on?

As to the hose issue, i would check those write ups on the hoses. You might have to replace all of them due to age. Also, are you having trouble with the HVAC control in the cab? Does it work correctly? Maybe checking that out too. Could have tranny fluid in the hoses which is an all together different issue.

Goodluck

Bill

 

For the most part, the noise has since stopped. I found the vacuum hose that was problematic, and fixed it. Now, I just need to fix the 4wd.

 

Since you think that you got the vacuum issue resolved, what exactly is happening to the 4WD??

Bill

 

Before I started working on it, the 4wd would not engage at all, unless I went backwards with it for a bit.

 

Do this,
1. Block the back wheels
2. Jack up the right front wheel so it is not touching the ground.
3. Start your vehicle up.
4. Engage the 4wd HI from the dash.
5. See if you can rotate the right front tire in either direction.
It should move a little in both directions then stop. That means it is locked in.
If it does not lock in, we need to go from there.

We need to find out if it is electrical, mechanical or vacuum related.

Bill