inconsistent idle

[darryl97420]

Lately I have noticed that the idle on my 91 is inconsistent. Upon first start of the day it hovers around 1100 rpm but after a drive it bounces from 1300 to 1800 then down to 1100/1300. Also I am hearing a vacuum sound but cannot pin point it.

Any suggestions?

 

[mr cribb]

broken vacuum line... check all your hoses running from the manifold.

you could clean your MAF sensor just for GP... use actual MAF sensor cleaner to do this, anything else will damage the MAF sensor.

Check your intake tube, they can crack and cause erratic idling like you're describing and a vacuum leaking sound. You're truck is 21 years old so this is entirely possible.

 

[malohnes]

Also check the grommet to the brake booster. I had a similar problem and I couldn't locate the problem until I decided to place the rubber lines. When I pulled the hose out of the booster, I found the grommet pulled out in pieces from dry rot.