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Rough idle

Tiny
AUGUST BERGY
  • MEMBER
  • 2006 CHEVROLET SUBURBAN
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
Hello friends, I have the vehicle listed above LT 5.3 vortec and it is idling rough. The engine codes are a random misfire, an emissions code saying it’s running lean, and a occasionally a knock sensor circuit to low code. I have put a ton of parts in it; all new coils, wires and plugs, new maf sensor, new knock sensor and harness, new camshaft position sensor, new oil switch, new intake manifold with new intake gaskets, all new O2 sensors, new evap canister, new purge solenoid, oh and I have a new K&N cold air intake. With all that I’ve put into it, it’s still idling rough but never stalls, it sputters when I accelerate but when I get up to speed it runs perfect. I am going to look into my fuel system. Does anyone have any info that would help me? Anything please? Lol I’ve put so much money into this thing!
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Monday, January 25th, 2021 AT 9:09 AM

6 Replies

Tiny
SEVAG P
  • MECHANIC
  • 405 POSTS
Hello,

It sounds like you have vacuum leak or low fuel pump pressure.

check our link below how to check vacuum leak.

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

Check our link how to check fuel pressure you must read 55 to 62 PSI.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Check the figures below, specific to your vehicle, fuel pressure, procedure how to install fuel pressure gauge and vacuum diagram.

Hope these helps. let us know if you need more help.

Thank you.

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Monday, January 25th, 2021 AT 11:25 AM
Tiny
AUGUST BERGY
  • MEMBER
  • 4 POSTS
Thank you for the help! I just checked under my hood to see if I even had a pc valve and my suburban doesn’t. So tomorrow I’m going to get it in the shop and check for a vacuum leak to see if it is the hose. And then I’ll do a fuel pressure test also.
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Monday, January 25th, 2021 AT 1:41 PM
Tiny
SEVAG P
  • MECHANIC
  • 405 POSTS
Hello,

yes let us know what happens with you, we are interested.

Thank you.
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Monday, January 25th, 2021 AT 3:27 PM
Tiny
AUGUST BERGY
  • MEMBER
  • 4 POSTS
Hey guys, sorry for the delay. I am a first year student in auto-mechanics. So I have done a fuel pressure test in my vehicle and it checked at 67 PSI, I also did a vacuum test with brake fluid and couldn’t find anything and the vacuum pressure gauge read at 16 PSI, but also I have figured out that the mass air flow sensor and MAP sensors are different, I have actually not put a new MAP sensor is only a new mass air flow sensor so that’s what I have come to. I will get back to you when I get the new MAP sensor in!
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Wednesday, January 27th, 2021 AT 10:43 AM
Tiny
AUGUST BERGY
  • MEMBER
  • 4 POSTS
I meant to say with brake cleaner*
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Wednesday, January 27th, 2021 AT 10:44 AM
Tiny
SEVAG P
  • MECHANIC
  • 405 POSTS
Hello,

Check connecting hoses to such items as a breather tube or EVAP system, also mass air flow is a possible cause, please send us live data if your scan tool has the function, for misfiring, mass air flow and o2 sensors function it helps for troubleshooting.

check our guide below for repair lean mixture codes.

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

let us know what happens.

thank you.
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Wednesday, January 27th, 2021 AT 11:37 AM

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