2007 yukon loss of power

[gfmadden330]

Well im rather new here, signed up a few months ago, just never got around to posting, but now i feel the need for assistance, especially when i have no clue if im right, wrong, or way off base..

So to start this off, i have a 2007 GMC yukob, 5.3, its got 250,105 on the odometer, and its had a slight puff of snoke at start up for a while, never was able to figure out what exactly it was, i believe it is a bad PCV, which im told on these requires replacing the entire valve cover. But before i was able to do anything, i needed so save some money for other issues in life. Well over that last 2 weeks, it has stopped smoking, which i thought, until now, was great, but i have lost power at acceleration, cant make it up hills without going WOT, and even then, it stutters and bucks. Ive also noticed a slick tick at start up, which goes away, and a tick at high RPM. Today i went to pass someone and smelled rotten eggs for the first time, so i guess my biggest questions is, are my cats clogged to the point of almost no flow, and could that cause the motor to make weird noises?

 

[Fless]

Moved you here from the 2021+ section.

 

[Geotrash]

Well im rather new here, signed up a few months ago, just never got around to posting, but now i feel the need for assistance, especially when i have no clue if im right, wrong, or way off base..

So to start this off, i have a 2007 GMC yukob, 5.3, its got 250,105 on the odometer, and its had a slight puff of snoke at start up for a while, never was able to figure out what exactly it was, i believe it is a bad PCV, which im told on these requires replacing the entire valve cover. But before i was able to do anything, i needed so save some money for other issues in life. Well over that last 2 weeks, it has stopped smoking, which i thought, until now, was great, but i have lost power at acceleration, cant make it up hills without going WOT, and even then, it stutters and bucks. Ive also noticed a slick tick at start up, which goes away, and a tick at high RPM. Today i went to pass someone and smelled rotten eggs for the first time, so i guess my biggest questions is, are my cats clogged to the point of almost no flow, and could that cause the motor to make weird noises?

Rotten egg smell can mean that the catalysts are either not working effectively or they're being overwhelmed with fuel. Given that you're experiencing a loss of power, I suspect either a misfire condition, plugged catalytic converter(s), a fuel delivery problem or an air metering problem. I'm guessing you're also getting a check engine light as well, but even if not, you'll need to have access to a decent scanner to see if any codes are present and/or capture the data from the various sensors. This would be sufficient: https://a.co/d/18hWY9K

Note that you will also need to purchase the GM module for the software within the Autel app itself. $20 annually, I believe.

 

[petethepug]

I think you nailed it with the cats being clogged and probably by those puffs of smoke. Start early and spray your exhaust down pipe & cat bolts with penetrating lube. They’ll likely be coming off.

First thing to do is pull the plugs and inspect for how it’s burning. Keep track of where they were pulled from.

Due to milage, a compression check is due. You have the option to proceed as either a tune up, with new plugs and wires or to deal with your potential low compression and any odd burn on the plugs.

Save yourself a lot of time and money and get a spark plug wire removal tool. The temptation to pull on any wire except on the boot leads to a wire failure that causes even more misfire problems.

 

[strutaeng]

Clogged cats will typically cause severe overheating issues, at least that was the case when I was helping diagnose my nephew's S10.

At idle everything on the live data seemed okay. We went for a drive around the block and pedal to metal was only able to go like 20 MPH, then temperature started climbing quickly. After 2 blocks we were limping back home.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

 

[gfmadden330]

Wow, i was not expecting the response i got! Thank you all! This weekend will be a long one, i will be doing a tune up, while im at it, i will check compression and do a leak down test. Ive already purchsed new plugs, coil packs, filters ect. Before purchasing this truck in march of 23, the prior owner supposedly did alot of top end work, how much of that was true is yet to be determined. But as for an engine light, i havent gotten one in quite some time, and last time it came on, it was a cat code, i cant remember the exact come, but it was a lean condition, downstream, if i remember correctly. Ive also looked into getting a new set of cats as a bolt on kit. An oem type from say rock auto, as well as new valve covers as i was informed that the PCV is built in and cant be replaced, so replacing the valve cover is the best option and instal a oil catch can as well.

On a side note, i am pretty decent around a motor, but this is my first GM, never worked on one in my 35 years on this earth, how difficult is a top/bottom refresh on these 5.3 motors

 

[gfmadden330]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

When i found this forum, i didnt know what to expect, but it has so far, completely amazed me at the wealth of knowledge, here is my Yukon, its seen better days, but its the family rig and my daily driver. Ive done some work, and have alot more to do. As soon as i get the motor issues figured out, i can continue cleaning her up, and make her look nice again!

 

[89Suburban]

Rotten egg smell can mean that the catalysts are either not working effectively or they're being overwhelmed with fuel. Given that you're experiencing a loss of power, I suspect either a misfire condition, plugged catalytic converter(s), a fuel delivery problem or an air metering problem. I'm guessing you're also getting a check engine light as well, but even if not, you'll need to have access to a decent scanner to see if any codes are present and/or capture the data from the various sensors. This would be sufficient: https://a.co/d/18hWY9K

Note that you will also need to purchase the GM module for the software within the Autel app itself. $20 annually, I believe.

This does the ABS power bleed?

 

[Joseph Garcia]

Wow, i was not expecting the response i got! Thank you all! This weekend will be a long one, i will be doing a tune up, while im at it, i will check compression and do a leak down test. Ive already purchsed new plugs, coil packs, filters ect. Before purchasing this truck in march of 23, the prior owner supposedly did alot of top end work, how much of that was true is yet to be determined. But as for an engine light, i havent gotten one in quite some time, and last time it came on, it was a cat code, i cant remember the exact come, but it was a lean condition, downstream, if i remember correctly. Ive also looked into getting a new set of cats as a bolt on kit. An oem type from say rock auto, as well as new valve covers as i was informed that the PCV is built in and cant be replaced, so replacing the valve cover is the best option and instal a oil catch can as well.

On a side note, i am pretty decent around a motor, but this is my first GM, never worked on one in my 35 years on this earth, how difficult is a top/bottom refresh on these 5.3 motors

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