Jump to content

Yukon feels like it's dragging or always going into a headwind

Juice75
 Share

Recommended Posts

Juice75 Enthusiast

Juice75

Posted
Posted

I've been chasing this issue for a few months, and need some help.

 

My 2002 Yukon 4.8l started losing a lot of low end power one day. The MPG dropped to 13.5-14, and it just always feels like I'm driving into a huge headwind. For example, when I'm on the highway and let off the gas, my truck starts slowing down quickly. It just doesn't coast. I don't think it's the brakes, because it's not consistent.

 

Here's what I've done so far:

  • Checked the plugs
  • Changed PCV, fuel filter and air filter
  • Cleaned the MAF and TB
  • Seafoam treatment through the brake booster vacuum line
  • Checked rear brakes
  • Getting a new fuel pump as we speak, because it wouldn't start yesterday. :(

 

Could it be something like the cats getting plugged? My truck has 150k miles on it. When the problem first happened, it was really bad. Then it slowly got better. One day, something felt like it broke loose, and it ran perfect for a week. Then after getting an oil change and the diff fluid changed, it started running a little off again.

 

Any ideas and help is appreciated.

 

Thanks!

Bad Bowtie2 Enthusiast

Bad Bowtie2

Posted
Posted (edited)

Have it scanned for codes- Just in case.

 

Try disconnecting the exhaust head-pipe from the exhaust manifolds. Then drive the SUV. If it runs A LOT better, then new CATS will probably be in order. :nopity:

 

Another thing, maybe the front calipers are sticking, causing brake drag? Or even the rear e-brake (inside linnings) are dragging? You will have to pull the wheels off and look.

 

Also, you'd be surprised what a front end alignment, and/or a transmission flush/rear diff fluid change can do to MPG's....

 

Something to ponder. :happysad:

 

Good luck.

Edited by Bad Bowtie2
  • Like 1
waumo1 Enthusiast

waumo1

Posted
Posted

If the brakes are dragging enough to cause the issue, they will be HOT when you stop from a good run. Like hot enough you will know it just by getting putting your hand on the wheel or near it.

 

When you let off the gas and feel the rapid slow down, does anything change if you shift into neutral?

Juice75 Enthusiast

Juice75

Posted
  • Author
Posted

Thanks guys for all the suggestions. Looks like the fuel pump may have been the culprit. I still need to put some more miles on it to tell, but so far, it's running great.

 

I'll post again after I get through a tank of gas to check the MPG. Keeping my fingers crossed that this was it.

  • Like 2
  • 2 weeks later...
Juice75 Enthusiast

Juice75

Posted
  • Author
Posted

Ok, so the fuel pump definitely made a difference....but it's not fixed. :( Went through a tank over Thanksgiving on the highway, and only got 14mpg. I used to get about 17.5mpg on they highway.

 

Since the fuel pump helped, I wonder if the issue is something else in the fuel system. Maybe the fuel pressure regulator?

 

Before the truck heats up to normal temp, it runs perfect. Or at least that's what I've felt so far. Once it hits normal temp, it just feels a little sluggish. Like the gas pedal has more travel before anything happens. It's not a huge difference, but definitely noticeable. I haven't check the fuel pressure yet, but that's next on the list.

TimmyG Senior Enthusiast

TimmyG

Posted
Posted

New plugs may help if it ran bad for a while

 

Sent from my ADR6400L using Tapatalk 2

 

 

Juice75 Enthusiast

Juice75

Posted
  • Author
Posted

I'll see if I can get my hands on a fuel pressure gauge. Read another post that talked about the PCM running in open loop when cold, and then closed loop once everything is heated up. And that the closed loop uses the O2 sensors, and it more susceptible to vacuum leaks.

 

So need to get a fuel pressure gauge and vacuum gauge. Can't wait to get this fixed. I've checked/changed/cleaned so many things, that my Yukon just has to run perfect once this last mystery is fixed. :)

yukon25008.1 Senior Enthusiast

yukon25008.1

Posted
Posted

Sounds like a clogged cat to me, I had that with an old 4.3 mini box truck, it couldnt get out of its own way..kept downshifting even on flat roads.. I cut that cat out..And it ran like a new truck!

Juice75 Enthusiast

Juice75

Posted
  • Author
Posted

yukon_denali_05 -what was your fuel pressure doing?

 

I checked mine today, and at idle, it stayed at 49. When I pulled the vacuum line off the regulator, it jumped up to 56, which is what I read it should do. I actually took a video of it, and the link is below. The second video is of a buzzing noise that comes from the TB when I turn the key on. Not sure if that is normal or not.

 

I also checked the vacuum, and at idle with the AC off, it held at 19. With the AC on, it dropped to 17. Does that sound about right?

 

If this rules out a vacuum leak and a fuel pressure issue (and that's a big 'if'), then here's my thinking now. The truck runs great until it reaches normal temp when the O2 sensors come into play. Could it be that one or multiple O2 sensors are incorrectly reading too lean, and causing it to run rich, making the MPG go down? At this point, I'm just guessing.

 

My next step is to get a back pressure test to rule out a clogged cat.

 

Fuel Pressure vid: http://thehawks.smugmug.com/photos/i-vZw3nBM/0/M/i-vZw3nBM-M.jpg

TB buzz vid: http://thehawks.smugmug.com/photos/i-rcLC42L/0/M/i-rcLC42L-M.jpg

yukon_denali_05 Enthusiast

yukon_denali_05

Posted
Posted

That sounds normal to me. Looks like fuel pressure appears to be good. I think you are on the right track with next guess being O2 sensors. How many miles on the truck and do you know if 02 sensors have been changed yet?

  • Like 1
Juice75 Enthusiast

Juice75

Posted
  • Author
Posted

I have 150k miles on my truck. As far as I know, the O2 sensors have never been changed. I bought the truck with 53k miles on it, and I know that I've never changed them.

 

Would I need to change all four, or just the two upstream from the cats?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Latest Articles

  • Posts

    • Grumpy Bear
      OCI, not when but why?

      By Grumpy Bear · Posted

      https://www.msn.com/en-us/autos/news/fuel-economy-stickers-don-t-tell-the-whole-story-aaa-data-reveals-why/ar-AA26ocHk?ocid=winp2fptaskbarhover&cvid=6a4122ea3dae47e5b8dfbed5d4fd3d55&cvpid=648f6b4fc2fa4eddb4c12893aeb957ed&ei=59
    • KARNUT
      OCI, not when but why?

      By KARNUT · Posted

      What’s missing in all this is patience and investment in the future. Buy a 170K starter home. Ten years later sell it invest in a more expensive home. Eventually you’ll have a 600K home and pay starter home payments. Buy a starter car. Maintain it well. Save the payments after it’s payed for then buy an expensive car if you desire. Buy a tumbler make your own coffee, pack your lunch. Cook your own dinner. Most importantly take care of your car.
    • Atlas
      OCI, not when but why?

      By Atlas · Posted

      People mislead themselves. Statistics are highly useful indicators.   Here's the tie-in to this thread. If an oil sample tests shows a wear indicator of 7 using cheaper ACDelco oil, and a wear indicator of 2 (lower = less wear) using a particular brand of Mobil oil, and wear has a linear relationship with engine lifespan, anyone could assume that Mobil is reducing wear by more than 50% (let's just say a 200% reduction for you red state people trying hard to do math) which leads to increasing engine life by 2x. Perhaps, in a vacuum, by itself, when dreamed by AI.   Yeah?! That's what the statistic is saying, isn't it?   No, it isn't. It didn't come out and say engine life is doubled. That's a very bad assumption, and a case of severe myopia by assuming something potentially untrue about the only data point in focus.   Average cost of a new car is 50k. You bet it is.   The median cost of a new car is more like 35k. Expensive cars are skewing the perception that "average" now means a $50k price of entry for a very average automobile. And that's not true. People who don't understand statistics twist the living heck out of them to mean all sorts of things they don't actually mean.   "Average" new car payment is $1000/month. Yep, it is. And in that number are all the $35k new car buyers who bring significant equity, and the $25k new car buyers who finance the car for a month just to get a rebate, and then pay it off. Know what isn't in that number? All the payments made by people who don't finance a car.   Picking one's own data point (don't have a car payment, never paid $50k for a new vehicle, my house cost $170k, I afforded a middle class lifestyle on $4.50/hr) is just a data point. Just like earning $25/hr in an area where the median home price is almost $1 Million is a data point. In fact, it's a lot of data points given that 80% of the US population lives in/around major cities. They're not idiots; the vast majority of them do it to make a living because that's where the big money is.   The highs have become higher, lows have become lower, and how your personal mileage varies is not truth for an entire country. At the same time you can't NOT acknowledge the data. While it doesn't paint YOUR personal picture, it certainly tints the reality that you also live in, as does your single data point.    
    • ShotgunZ71
      Poll: Does your truck have the rear window leak?

      By ShotgunZ71 · Posted

      Glad you had success with it. I did as well, but about 5-6 months later it returned. Tried again, same result. This was after the dealer made several attempts and never even got it to slow down.
    • KARNUT
      Gas Prices

      By KARNUT · Posted

      3.15 Kroger’s in Montgomery Tx

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...