Loud pop under hood while driving

JENFOX360

MEMBER
2011 CHEVROLET SILVERADO
5.3L
V8
4WD
AUTOMATIC
116,000 MILES

Heard a loud pop sound think coming from the passenger side under the hood. Pulled over took still runs. Check engine light flashing. Decide I'm a few miles from home so I drive more and as accelerate it makes a tapping noise. The truck still drives but when stopped at stop sign it idles like it will. Decided to park it and tow. No smoke. No overheating. No fluid splattered over engine. No bad smell. No obvious answer by looking under hood. Trouble codes were in 2nd module. Lean in bank 1 and 2. Misfire in cylinder 4.
Any guesses where to start my investigation into what to fix?

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,896 POSTS

By any chance, have you removed the number 4 spark plug for inspection? It didn't blow out of the head by any chance? The bang makes me ask.

Also, can you record it running and upload it so I can hear it?

Let me know.

Take care and God Bless,
Joe

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Friday, February 5th, 2021 AT 8:27 PM

JENFOX360

MEMBER
4 POSTS

Thanks for replying. No I haven't taken out the plug. I never can get one out. I tried before when that misfire code came up to see if there was coolant in the cylinder, troubleshooting if I had a head gasket leak. Couldn't get the cable off the thing. I'll try tomorrow and see if I can. Also I'll see if it starts. I haven't tried since it was towed back. I'll record the noise. It got worse when I was accelerating. We have been having trouble with it for a while. A friend got her mechanic friend to scan it and clear reset the computer. It runs for a while ok then starts to act up. A little more info: we changed all the spark plugs, cables, air filter, oil, and the MAP sensor over the last 4 months
Before we did the Map sensor it had code for to rich in bank 1 and 2. And now it says too lean in both. Also the mechanic that reset the computer said it scanned and said it had 70% alcohol in the fuel. Which isn't true obviously. So we were not sure what was going on. If a sensor is bad or if the computer is bad and lies to the sensors. Now that this happened I'm stumped, lol. Thanks for your help I will message you back ASAP tomorrow.

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Friday, February 5th, 2021 AT 9:17 PM

JENFOX360

MEMBER
4 POSTS

Good morning. I started the truck and it had no prob starting but yeah the noise is still there. I didn't want to tub it too long in case it causes more of a problem. I hope you know what it is! I'll try to get the #4 plug out. Thank you

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Saturday, February 6th, 2021 AT 7:31 AM

JENFOX360

MEMBER
4 POSTS

Okay, so I took the spark plug off, or should I say it was already out apparently. I noticed right away that the cable connected to the other end was already halfway off so I just jiggled it off and it was like this.

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Saturday, February 6th, 2021 AT 8:11 AM

JACOBANDNICKOLAS

MECHANIC
109,896 POSTS

Hi,

I suspect that was the noise you heard. Are you able to get a new spark plug and reinstall it into that cylinder. By looking at the darkness on the threads, I suspect it was loose for some time.

Let me know.

Joe