Turning off and losing power?

1988 CHEVROLET CHEYENNE
300,000 MILES • 5.7L • V8 • 4WD • AUTOMATIC
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CHEVYKID98
  • MEMBER
  • 1 POST
When I drive my truck, it runs perfectly fine for like 30 seconds and starts giving trouble when I brake. When I brake and try to give it gas it jerks and barely goes when I have the gas pushed to the floor. Like there is no gas but there is gas in the truck. It never used to do this and I'm not sure. We replaced the original engine with a 1997 suburban 350 engine and never had problems. Even with a rebuilt transmission installed not too long ago.
Feb 14, 2023 at 7:11 AM
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JACOBANDNICKOLAS
  • ✓Experienced Mechanic
  • 110,244 POSTS
Hi,

When you press the brake, you use the engine vacuum to assist braking via the vacuum brake booster behind the brake master cylinder. Since this is when you notice the issue, it sounds like you may have a vacuum leak at the booster or elsewhere under the hood. A large loss of engine vacuum will cause the engine to run poorly, rough, and even stall.

Let's start by testing for a leak. Here is a link that explains how to locate and repair an engine vacuum leak. Take a look through it and let me know if you are comfortable performing the procedure.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know what you find.

Take care,

Joe
Feb 14, 2023 at 9:03 AM
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