C4 Vacuum Leak
Thread Starter
Intermediate
Joined: Sep 2005
Posts: 25
Likes: 0
C4 Vacuum Leak
I have an '89 C4 that I believe has a vacuum leak.
I just had back surgery and am not able to work on it my self, so I have a mechanic that I have trusted in the past who says he can work it once he gets the '57 chevy out of the bay. He wants to make sure my car is inside his shop. I am having him do the back brakes and look into the vacuum leak.
What I am seeing is an up tick in RPM of about 400 and idle brake after it has warmed up is abut 900 instead of the normal 600. The other indicator is that the instant mileage reading and the range go to zero! While driving I may see the readings reappear temporarily. Seems like a losse hose or a break in the line.
Any ideas on where to look?
Thanks
I just had back surgery and am not able to work on it my self, so I have a mechanic that I have trusted in the past who says he can work it once he gets the '57 chevy out of the bay. He wants to make sure my car is inside his shop. I am having him do the back brakes and look into the vacuum leak.
What I am seeing is an up tick in RPM of about 400 and idle brake after it has warmed up is abut 900 instead of the normal 600. The other indicator is that the instant mileage reading and the range go to zero! While driving I may see the readings reappear temporarily. Seems like a losse hose or a break in the line.
Any ideas on where to look?
Thanks
Instructor
Joined: Jul 2011
Posts: 128
Likes: 0
From: Vancouver WA
if you can get a scan tool and measure fuel trim, your counts should be 120-130, if they are WAY out of range (MUCH higher) look for a vacuum leak.
if you don't have a scan tool, spray some carb cleaner at the base of each fuel injector and listen for a change in engine speed. spray around the EGR (common place), vacuum hoses (duh!), break booster, throttle body.
if you don't have a scan tool, spray some carb cleaner at the base of each fuel injector and listen for a change in engine speed. spray around the EGR (common place), vacuum hoses (duh!), break booster, throttle body.
