Weak 5.3 V8

[BlitherinIdiot]

I am towing my 18' Boat (3,700 lbs.) with either my 2003 Yukon or my 2000 Chevy Z71. Both vehicles have the 5.3 with the 3.73 gears and factory tires (265 Yukon, 245 Chevy). The Yukon has 45,000 miles and the Chevy has 51,000. My problem is the Chevy is way down on power compared to the Yukon. Towing at 70-75 on the interstate gets me 10-11 mpg. The Yukon typically gets 13-14. The Chevy also drops down into 3rd on anything but flat ground. The Yukon will hold OD on all but big hills. I do not tow in OD unless I am on the interstate and keep it in third if the transmission is hunting a lot.

 

I just had the transmission serviced, intake manifold cleaned, fuel injection service, and run seafoam every few tanks. Any ideas why the Chevy is a dog compared to the Yukon?

 

Thanks.

 

 

Chris

[asilverblazer]

I am towing my 18' Boat (3,700 lbs.) with either my 2003 Yukon or my 2000 Chevy Z71. Both vehicles have the 5.3 with the 3.73 gears and factory tires (265 Yukon, 245 Chevy). The Yukon has 45,000 miles and the Chevy has 51,000. My problem is the Chevy is way down on power compared to the Yukon. Towing at 70-75 on the interstate gets me 10-11 mpg. The Yukon typically gets 13-14. The Chevy also drops down into 3rd on anything but flat ground. The Yukon will hold OD on all but big hills. I do not tow in OD unless I am on the interstate and keep it in third if the transmission is hunting a lot.

 

I just had the transmission serviced, intake manifold cleaned, fuel injection service, and run seafoam every few tanks. Any ideas why the Chevy is a dog compared to the Yukon?

 

Thanks.

 

 

Chris

 

The 2003 should be putting out more power than the 2000. I figured the weight difference and taller tire would have consumed it though.

[redvett]

Towing a trailer that fast is dangerous at best and probably illigal in any state. Here in MI its 65 mph.

[BlitherinIdiot]

The 2003 should be putting out more power than the 2000. I figured the weight difference and taller tire would have consumed it though.

 

I thought both model years were rated at 285 h.p. I'll do a search and double check that and the torque numbers. Thanks.

[tnord]

Towing a trailer that fast is dangerous at best and probably illigal in any state. Here in MI its 65 mph.

 

dangerous? give me a break. perfectly legal to haul at 70mph through KS, MO, IA, and MN as well. if ANYONE is going to err on the side of being conservative little safety queens, it's the gov't and the DOT.

 

<----hauls 5000 lbs all the time at 75mph with appropriate brake pads and dual axle electric brakes controlled from the comfort of the truck cabin.

[xsports33]

Towing a trailer that fast is dangerous at best and probably illigal in any state. Here in MI its 65 mph.

 

dangerous? give me a break. perfectly legal to haul at 70mph through KS, MO, IA, and MN as well. if ANYONE is going to err on the side of being conservative little safety queens, it's the gov't and the DOT.

 

<----hauls 5000 lbs all the time at 75mph with appropriate brake pads and dual axle electric brakes controlled from the comfort of the truck cabin.

 

 

Right on brutha!!! I tow around 75-85mph from southern California to AZ/NV area. Anything could be deemed dangerous if you don't know what your doing.

[tnord]

to add some value for the OP.....

 

i thought my 5.3 felt flat as hell last year when towing and had pretty much the exact same symptoms you describe. 10-11mpg pulling a 5000lb car hauler + race car behind me between 70-75mph, any headwind or hill and it's 3rd gear all the way.

 

i had a bad fuel pump and leaky intake manifold gasket replaced this fall, and the truck does feel stronger. i have yet to tow with it though.

[mrsilv04]

I've pulled my parents camper (6500#) with both my truck and Dad's truck. Both are 1/2 ton extended cab 2WD with 5.3's. Dad's is a '00 Sierra with a 3.73, mine is an '04 Silverado with a 3.42.

 

Dad and I both agree that my truck outpulls his truck, even though his is better set up for pulling with the 3.73 rear end and aftermarket suspension modifications. Mine only has the factory towing pack and an aftermarket controller.

 

My truck could pull that camper all day long at 70-75mph. Of course, we're using a proper hitch, a sway bar, and a load balancer system.

 

I'd say it is the engine. His is set up better than mine for towing, and the years are just about the same as yours. The raw numbers are fairly similar... but how do the torque curves look betweeen the two? Anyone have that data?

[BlitherinIdiot]

to add some value for the OP.....

 

i thought my 5.3 felt flat as hell last year when towing and had pretty much the exact same symptoms you describe. 10-11mpg pulling a 5000lb car hauler + race car behind me between 70-75mph, any headwind or hill and it's 3rd gear all the way.

 

i had a bad fuel pump and leaky intake manifold gasket replaced this fall, and the truck does feel stronger. i have yet to tow with it though.

 

 

What led you to replace the intake manifold gasket and fuel pump? Was it trial and error or were these diagnosed as being bad by the tech? Thanks!

 

Chris

[BlitherinIdiot]

I'd say it is the engine. His is set up better than mine for towing, and the years are just about the same as yours. The raw numbers are fairly similar... but how do the torque curves look betweeen the two? Anyone have that data?

 

Thanks for the input. On paper, your dad's truck should out tow your truck, but real world is different. Like you mentioned, the raw torque numbers are 325 ft/lbs@4000 rpms for both model years. Maybe the curves are different as you have suggested. I guess I will see if I can find a chart for the '00 and '03 to compare. Of course I may just have a sick engine.

 

Chris

[tnord]

well my truck would hardly EVER start on the first try when cold, and i had heard of issues with the fuel pump. so after about a year of this i finally got tired of it and took it in to get fixed and swallow the bill. while they had it i said "tell me everything that's wrong with this truck." i drive racecars on the weekends with the GM and parts manager of the place, and the service writer, service manager, tech knew this, so i knew they wouldn't screw me.

 

they brought me back a laundry list of stuff, and i picked out what i wanted fixed. they did some kind of vacuum test to find the leaky manifold gasket iirc.

[harescrambler]

well my truck would hardly EVER start on the first try when cold, and i had heard of issues with the fuel pump. so after about a year of this i finally got tired of it and took it in to get fixed and swallow the bill. while they had it i said "tell me everything that's wrong with this truck." i drive racecars on the weekends with the GM and parts manager of the place, and the service writer, service manager, tech knew this, so i knew they wouldn't screw me.

 

they brought me back a laundry list of stuff, and i picked out what i wanted fixed. they did some kind of vacuum test to find the leaky manifold gasket iirc.

 

I had a similar problem and replaced the fuel pressure regulator with now problems since. "knock on wood" Now I'm starting to get some bad mileage but can't really narrow that down since I like the sound of my headers and it's colder out now.

[tnord]

i replaced the FPR, plugs, wires, fuel, and air filter all before i was pretty confident it was a fuel pump.

[VORTEC 6000]

when you towing somthing keep it in third

and you will see The difference

[tnord]

i'm sure i would see the difference, and i bet i'd get <10mpg as well with the motor making all kinds of noise.

 

i should not have to put it in third across iowa/kansas/nebraska because of a 5mph headwind and a 2 degree incline at 70mph. the truck has 2000+ revs at that point and an open trailer with max weight of 5000lbs. if i had a v6 i would expect to leave it in third, but not with the 5.3 or better.