throttle delay stumble?

1988 CHEVROLET 1500
124,000 MILES • 5.7L • V8 • 2WD • AUTOMATIC
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SUKCHB
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  • 1 POST
I changed the EGR valve and MAP sensor in my truck. When I hook up the vacuum lines properly, there is a huge throttle delay at low revolutions and the check engine light appear. It idles perfectly and drives perfectly when cold for the first minute. When I take the vacuum line off the EGR valve and just let it hang free, it works perfectly.
Jun 9, 2025 at 11:53 PM
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STRAILER
  • ✓Experienced Mechanic
  • 55,604 POSTS
Yep, the EGR valve is opening too early. I would replace the EGR vacuum controller which is located at the intake manifold near the distributor. If you cannot find one you might try Ebay or get a vacuum delay valve from Amazon or the parts store. Check out the images (below). Please let us know what happens.
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Jun 10, 2025 at 11:08 AM
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