Vacuum problems
Thread Starter
ZR1TG
Joined: May 2005
Posts: 875
Likes: 235
From: South florida
Vacuum problems
Hey guys have a 1993 anniversary zr1 7k miles. The car runs perfect. Idles perfect. Secondaries open up and revs freely to 7k.
problem is with vacuum pump. It just stays running with not the slightest hint of building up vacuum. I was able to take plastic line out at throttle body ( passenger side ) and if I put my finger over the line the pump stops instantly. So pump seems ok. I am hoping to not have to take this plenum off the car. All of the vacuum lines I can see look excellent and not at all loose. Again the car only has 7k miles. Is it possible that ecm is causing the problem and not a vacuum leak. ? I have a mity vac but not sure where to start.
I tried checking for error codes but found that can’t be done with lt5 not for module 4. My scanner is too new for this car. Should I find a scanner that will work ?
anyone have experience with this ?
thanks
hardhattg
problem is with vacuum pump. It just stays running with not the slightest hint of building up vacuum. I was able to take plastic line out at throttle body ( passenger side ) and if I put my finger over the line the pump stops instantly. So pump seems ok. I am hoping to not have to take this plenum off the car. All of the vacuum lines I can see look excellent and not at all loose. Again the car only has 7k miles. Is it possible that ecm is causing the problem and not a vacuum leak. ? I have a mity vac but not sure where to start.
I tried checking for error codes but found that can’t be done with lt5 not for module 4. My scanner is too new for this car. Should I find a scanner that will work ?
anyone have experience with this ?
thanks
hardhattg
Race Director
Joined: Feb 2002
Posts: 11,622
Likes: 1,056
From: Compound in the Grove, Ga.
2026 Corvette of the Year Finalist - Unmodified
2025 C4 of the Year Winner - Unmodified
2024 C4 of the Year Finalist - Unmodified
2020 C3 of the Year Finalist - Unmodified
2019 C4 of Year Finalist (performance mods)
2018 C4 of Year Finalist
2015 C4 of the Year Finalist
St. Jude Donor '16
Unfortunately it sounds like you may have to pull the plenum to find the source of the leak.
Le Mans Master
Joined: Oct 2004
Posts: 6,314
Likes: 508
From: South-central Missouri
Pulling the plenum is a "rite of passage" for any new ZR-1 owner! Jerrys Gaskets has thee replacement gasket you will need. Chances are there is a rotted rubber connector or the like. Jerry has everything you might need to repair the vacuum harness.
Good luck, and welcome to the BROTHERHOOD OF THE BEAST!!!
Good luck, and welcome to the BROTHERHOOD OF THE BEAST!!!
Drifting
Joined: Oct 2003
Posts: 1,356
Likes: 78
From: Kamakura, Japan
Mine was the check valve, but as mentioned you’ll have to pull the plenum to repair either way.
Check out Cliff’s post #121.
https://www.corvetteforum.com/forums...-500-hp-7.html
Check out Cliff’s post #121.
https://www.corvetteforum.com/forums...-500-hp-7.html
3rd Gear
Joined: Dec 2020
Posts: 3
Likes: 0
From: Pittsburgh
hardhattg- I have a 92 Z and I have the same issue. I have no problems with opening up the secondaries at WOT but I do notice the leak. When I have my key on "on" pump runs stops for a few seconds and then runs again. If I plug the line where you said the pump stops. The question I have been having is why try to find the leak if everything is working fine from idle to opening up secondaries? Am I missing something?
Drifting
Joined: Oct 2003
Posts: 1,356
Likes: 78
From: Kamakura, Japan
hardhattg- I have a 92 Z and I have the same issue. I have no problems with opening up the secondaries at WOT but I do notice the leak. When I have my key on "on" pump runs stops for a few seconds and then runs again. If I plug the line where you said the pump stops. The question I have been having is why try to find the leak if everything is working fine from idle to opening up secondaries? Am I missing something?
Thread Starter
ZR1TG
Joined: May 2005
Posts: 875
Likes: 235
From: South florida
For now I am just going to let it go. The car runs perfect , idles fine , revs like crazy . I may disconnect power to vacuum pump until the day comes to take plenum off . I am hoping to have car judged by ncrs this November and just don’t want to take it all part before then , when it does not seem to be effected at all or maybe I will just block the line from inside the line and reconnect , so pump functions but shuts right off.
I may be missing something but car does not seem to be effected by what is apparently a leak and with only 7k miles and never been apart I just don’t want to dig into it for only that reason.
I may be missing something but car does not seem to be effected by what is apparently a leak and with only 7k miles and never been apart I just don’t want to dig into it for only that reason.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski