Started running sluggish and the idle was up and down and would shut off?

Tiny
ZAKKARY
  • MEMBER
  • 1998 CHEVROLET 1500
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 100,000 MILES
It started running sluggishly and the idle was up and down and would shut off sometimes when you drove it. But I replaced the timing chain and sprockets because it jumped time just a little bit and crankshaft sensor and distributor/camshaft sensor and re-tuned it with a jet performance tool. I also ran seafoam through it. It will start but it squeals while idling or driving which is probably my powering steering pulley and has a rough idle that goes up and down. Also sounds like a knock in the bottom end I was just curious if it could be something simple before I switch the engine. (Was told the engine and transmission was basically new when I got which it did look clean)
Wednesday, April 5th, 2023 AT 8:52 AM

5 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,356 POSTS
It sounds like you could have low compression on one cylinder, a broken valve spring or vacuum leak. Can you please shoot a quick video with your phone so I can hear the noise? That way I can tell for sure what's going on for sure. You can upload it here with your response. Also, this guide may help:

https://www.2carpros.com/articles/stall-at-idle

And use this guide when the engine is cold only:

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

Let us know what happens and please upload pictures or videos of the problem so we can see what's going on.

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Wednesday, April 5th, 2023 AT 9:49 AM
Tiny
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Here.
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Wednesday, April 5th, 2023 AT 10:05 AM
Tiny
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You can also hear the vacuum idle up and down, but you can barely hear it in the video.
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Wednesday, April 5th, 2023 AT 10:09 AM
Tiny
KEN L
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Thanks for the video, it helps. I would remove the serpentine belt and start the engine for a few seconds to see if the squeaking noise goes away, if so, spin the front accessories to see which pulley is making the noise. Next, I would do a compression test because you may have a head gasket blown between two cylinders. Please use this guide:

https://www.2carpros.com/articles/how-to-test-engine-compression

Please go over this guide and report back.
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Thursday, April 6th, 2023 AT 11:07 AM
Tiny
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I'll look when I get the time thanks for the assistance!
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Thursday, April 6th, 2023 AT 8:16 PM

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