P0410 Help !!
Thread Starter
Intermediate
Joined: Mar 2025
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If I had understood how the vacuum system worked, then I would have immediately checked for a vacuum leak somewhere.
Question: Will the HVAC supply vacuum leak affect the vacuum test results im taking from the Brakebooster vacuum supply hose?
(I posted another reply with a picture for reference)
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
I doubt you will even see a big change in manifold vacuum with that small hose leak whether it’s an HVAC or the AIR system…looks like you have 19 inches of vacuum…do you have a leak right now ??..if you had a scan tool you could look at your fuel trims…just get the leak fixed.
Thread Starter
Intermediate
Joined: Mar 2025
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I doubt you will even see a big change in manifold vacuum with that small hose leak whether it’s an HVAC or the AIR system…looks like you have 19 inches of vacuum…do you have a leak right now ??..if you had a scan tool you could look at your fuel trims…just get the leak fixed.
I installed new intake manifold gaskets (as a good measure and to ensure a good seal and minimize vacuum leaks at the manifold. I replaced the HVAC supply line down to supply the HVAC and AIR system. I ended up routing my own line because I want easier access and want to minimize the risk of damaging the vacuum line anytime I have to remove the intake manifold... the OEM small HVAC vacuum line is a PITA anyways when R&R the intake manifold.
- Checked for vacuum out the AIR solenoid (result: 17in/hg)
- Checked for vacuum at the AIR shut off valve
(result: 17in/hg)
- P0410 is now gone and the AIR system is functioning properly
Although I did not use a scan tool to check the voltage drop on the O2 sensors related to the AIR system, I will be taking the corvette to my buddy’s shop and checking everything out then.
For now everything seems to be operational, however the vacuum supply to the HVAC and AIR (being 17in/hg) seems a bit on the lower end.. is this something to worry about?
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Joined: Sep 2013
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From: Cape Coral, Florida
Was the engine fully warmed up when you took this reading ??…try taking your reading elsewhere on the intake manifold perhaps the brake booster…if 17 wouldn’t worry about it …is the engine “cammed” ??
Tech Contributor
Joined: Jan 2007
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From: Dyer, IN
That does not help if the hose you are using is collapsing. Get yourself a set of adapters here. Well worth the cost.
Thread Starter
Intermediate
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Vacuum Readings with engine full warmed during idle:
- HVAC supply: 18in/hg
- Brake booster supply: 19in/hg
Is it normal for vacuum to read lower when engine is still cold?
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
Yes, that is normal and that is why I asked if the engine was fully warmed up…engine internals like pistons rings will seal better and also engine vacuum decreases 1 inch of Hg every 1000 feet in altitude…key on engine off your BARO on a scan tool should read 101 kPa or approximately 14.7 psi at sea level…a skewed MAP sensor can really effect engine performance and may even prevent it from starting.
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Thread Starter
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Final Update and Solution.
Engine code P0410 was cleared a week ago, driven, and passed CA smog with flying colors. My issue was just the intake vacuum line which feeds the AIR and HVAC, was broken somewhere under the battery tray, most likely due to battery acid leak during previous ownership.
Driverside and passenger side air check valves may or may not have gone bad, but they were replaced anyways… they were bound to go bad sooner or later.
Thanks for the help everyone who contributed to my successful repair
@C5 Diag @lucky131969
Engine code P0410 was cleared a week ago, driven, and passed CA smog with flying colors. My issue was just the intake vacuum line which feeds the AIR and HVAC, was broken somewhere under the battery tray, most likely due to battery acid leak during previous ownership.
Driverside and passenger side air check valves may or may not have gone bad, but they were replaced anyways… they were bound to go bad sooner or later.
Thanks for the help everyone who contributed to my successful repair
@C5 Diag @lucky131969
Tech Contributor
Joined: Jan 2007
Posts: 19,470
Likes: 1,171
From: Dyer, IN
Final Update and Solution.
Engine code P0410 was cleared a week ago, driven, and passed CA smog with flying colors. My issue was just the intake vacuum line which feeds the AIR and HVAC, was broken somewhere under the battery tray, most likely due to battery acid leak during previous ownership.
Driverside and passenger side air check valves may or may not have gone bad, but they were replaced anyways… they were bound to go bad sooner or later.
Thanks for the help everyone who contributed to my successful repair
@C5 Diag @lucky131969
Engine code P0410 was cleared a week ago, driven, and passed CA smog with flying colors. My issue was just the intake vacuum line which feeds the AIR and HVAC, was broken somewhere under the battery tray, most likely due to battery acid leak during previous ownership.
Driverside and passenger side air check valves may or may not have gone bad, but they were replaced anyways… they were bound to go bad sooner or later.
Thanks for the help everyone who contributed to my successful repair
@C5 Diag @lucky131969
Glad this worked out for you. I just went through this myself this weekend on my 1999. In my case, the solenoid went bad in the pump(97-99 is different than yours).