4x4 issue
#1
![Default](https://blazerforum.com/forum/images/icons/icon1.gif)
My 99 with the 4 button 4wd takes a while but it will go into 4wd on the auto and hi range setting. Goes in and out of 4low just fine. I put a new switch in the dash and that stopped the service 4wd light. I almost positive now its a vacuum issue cuz it will pop out of 4wd on acceleration. Anyone else have this issue?
#2
Guest
Posts: n/a
![Default](https://blazerforum.com/forum/images/icons/icon1.gif)
Well yes I did but I'm 3 button, it would come out with a bang and it was vacuum. Not sure how it relates to yours.
When yours comes out do you have a bang in the front diff.
I'm not going to come back cause that's all I can really say, I know nothing about the four button set-up. Good luck!
When yours comes out do you have a bang in the front diff.
I'm not going to come back cause that's all I can really say, I know nothing about the four button set-up. Good luck!
#4
![Default](https://blazerforum.com/forum/images/icons/icon1.gif)
Probably a vacuum leak in the HVAC or 4WD system(s), or possibly just a bad vacuum check valve. The valve keeps vacuum in the systems when the engine vacuum is low, (acceleration) to prevent the vacuum actuators from reverting to their default positions. 4WD goes to 2WD and HVAC goes to defrost.
#5
![Default](https://blazerforum.com/forum/images/icons/icon1.gif)
OK thats kinda what i was thinking. I plan on changing all the vac lines once i get time. The vacuum valve is this the one mounted at the firewall? I may as well replace it while im right there. Thanks for the info
Last edited by Justin56; 12-18-2013 at 08:46 AM.
#6
![Default](https://blazerforum.com/forum/images/icons/icon1.gif)
Follow the 7/32" vacuum line from the supply port. #4 in the image below:
![Name: mxiga039amu_gm_intake_manifold_zps6e2dc7dd.jpg
Views: 576
Size: 49.6 KB](https://blazerforum.com/forum/attachments/2nd-generation-s-series-1995-2005-tech-41/31495d1501271945-4x4-issue-mxiga039amu_gm_intake_manifold_zps6e2dc7dd.jpg)
It will connect to the vacuum check valve, (might not look exactly like the one in the image below). This image might help with vacuum line routing:
![Name: mxiga039amu_gm_intake_manifold_zps6e2dc7dd.jpg
Views: 576
Size: 49.6 KB](https://blazerforum.com/forum/attachments/2nd-generation-s-series-1995-2005-tech-41/31495d1501271945-4x4-issue-mxiga039amu_gm_intake_manifold_zps6e2dc7dd.jpg)
It will connect to the vacuum check valve, (might not look exactly like the one in the image below). This image might help with vacuum line routing:
![Name: Vacuumlines.jpg
Views: 1328
Size: 64.9 KB](https://blazerforum.com/forum/attachments/2nd-generation-s-series-1995-2005-tech-41/31496d1501271945-4x4-issue-vacuumlines.jpg)
Thread
Thread Starter
Forum
Replies
Last Post
brian79z
Steering, Suspension & Drivetrain
32
02-23-2015 07:13 PM
J.R. Clay
1st Generation S-series (1983-1994) Tech
5
03-16-2011 12:33 AM
extreme
2nd Generation S-series (1995-2005) Tech
4
01-05-2010 07:29 AM