running rough

1997 CHEVROLET SILVERADO

160,000 MILES • 5.7L • V8 • 2WD • AUTOMATIC

CHEVY1234

MEMBER
4 POSTS

So, the upper intake gasket along with two fuel injectors were replaced on my 5.7l vortec. I did not do the repairs so i can only go off of what the other person (my brother) says. I have no taillights which worked before, the truck will stay running sometimes but it's very rough. as far as the rough running. He said he thinks he sucked a paper towel into one of the intake ports, but he is not positive. Would that make it run rough? I have asked a few people and keep getting mixed answers. How would i even check that? The taillights I'm hoping it's just a fuse but i don't know if he fried something or what. I tried plugging the scanner in but all I'm getting is an O2 sensor code that's been there since i owned it. I just need to figure this out. Thank you.

Feb 27, 2022 at 12:34 AM

JACOBANDNICKOLAS

✓Experienced Mechanic
110,240 POSTS

Hi,

Wow. If a paper towel was drawn into the intake, yes that will cause issues. If that is a possibility, you really should remove the throttle body and see if you can locate it.

If you look below, I provided the directions for the removal and installation of the throttle body. This is where I would start.

First, do this so we can confirm there is nothing blocking the intake.

Let me know what you find or if you have other questions.

Take care,

Joe

See pics below.

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Feb 27, 2022 at 12:46 PM

CHEVY1234

MEMBER
4 POSTS

I took the upper plenum off and checked all 8 ports. He said he had one in each port, so nothing went in there. If he left one in, put everything back together, and started it. Wouldn’t it get sucked into the engine?

Feb 27, 2022 at 7:57 PM

JACOBANDNICKOLAS

✓Experienced Mechanic
110,240 POSTS

Hi,

It could have been drawn in by vacuum, but that would really depend on size. Plus, where would it have gone? I would like to think it got burned up, but it may have caused other issues.

Have you scanned it to see if there is a specific cylinder or cylinders causing the issue?

Let me know.

Joe

Feb 28, 2022 at 6:40 AM

CHEVY1234

MEMBER
4 POSTS

I ran codes and there is only an O2 sensor that’s been there since I’ve had it. I also checked cylinder compression an all are between 120-140.

Feb 28, 2022 at 8:47 PM

JACOBANDNICKOLAS

✓Experienced Mechanic
110,240 POSTS

Hi,

If it is a rough idle, have you checked to see if there are any vacuum leaks, and have you checked fuel pressure? Also, let me know what the code is for the O2 sensor. It could be causing issues.

Here is a link that explains how to check for vacuum issues:

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

Let me know.

Joe

Mar 1, 2022 at 11:34 AM

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