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Hi all -- Been having some strange behavior on the 92 Camaro V6. When I have her in park/neutral while idling and press down/release on the brakes, the engine RPMs spike and then dip. The behavior is 100% consistent at either cool or hot engine temperatures. I've attached a plot of a log dump I pulled from TunerProRT so you can see the behavior -- I also included the battery voltage on there, too, which shows a little bit of similar behavior though it's probably just reacting to the engine load.
I thought I caught all of the vacuum leak problems and bad hoses on this vehicle but maybe I missed something around the brake booster? Any ideas?
Have you tested the brake booster itself for a vacuum leak. Check to see that it holds a vacuum. Also check the 1-way valve/fitting that the hose connects to.
I have not but I just did some research on how to check — I’ll report back in after checking the hose, the check valve, and the booster itself. Thanks!
A quick check is to run the engine for a few min to build up vacuum in the booster. Rev the engine a few times will help to get the maximum vacuum. Then shut off the engine. Wait 5 min or so and depress the brake with eng off. There should be enough vacuum stored in the booster for at least one or maybe two assisted brake applies then get hard. If there isn't you have a leak. Possibly booster diaphragm or check valve. This would cause a LARGE vacuum leak that would definitely cause idle issues. Especially on a smaller engine like your V6.
A quick check is to run the engine for a few min to build up vacuum in the booster. Rev the engine a few times will help to get the maximum vacuum. Then shut off the engine. Wait 5 min or so and depress the brake with eng off. There should be enough vacuum stored in the booster for at least one or maybe two assisted brake applies then get hard. If there isn't you have a leak. Possibly booster diaphragm or check valve. This would cause a LARGE vacuum leak that would definitely cause idle issues. Especially on a smaller engine like your V6.
I got about 1 and a half assisted pumps after waiting 5-10 minutes -- I haven't checked the hose and check valve yet but maybe my booster is fine after all. I'll check the rest of the components this evening.
Last edited by cosmonautpg; Jul 29, 2020 at 02:53 PM.
Reason: typo
Quick update -- after removing and re-installing the hose and check valve, it seemed to get better. Might have been a bad seal but the components are still old. Going to replace the hose and check valve this week and see if it becomes more stable.
