2004 GMC Yukon flex fuel edition issues

[bmpalevich]

Hello I have a 2004 GMC Yukon flex fuel edition I never use the stuff!!.. I am having issues with fuel consumption I don't get what's expected out of this truck it's got 179k miles on it no check engine light, the damn thing eats fuel 150 ish miles then I'm empty.. I've replaced 02 sensors map maf fuel pressure regulator cats spark plugs wires breaks rotors calipers transmission is a year old with less than 30k on it. It's a problem I've had for some time and I'm just down right sick of it I see most people getting 15mpg city and 20 mpg hwy with their's in the same year range same model.. what do you guys think could possibly be going on with my huge fuel loss? I have no leaks I don't smell gas

 

[Fless]

Welcome to TYF from a mile above mean sea level.

15 mpg hwy might be attainable, or a stretch for gas; it depends a lot on how it's driven. Higher octane gas can help the mileage, too; not sure what you run or at what altitude.

Now, you might want to take a look at your ST and LT (short term, long term) fuel trims at idle and at 2000 rpm with a scanner. I know that can be a lot of numbers with both banks but they are all important to help see what's going on. Maybe post them up or upload scanner screen shots.

 

[OR VietVet]

Welcome to the forum from Oregon.

Like @Fless said, how is it driven, altitude, brand and octane of fuel? Lots of short trips? Mostly highway? Does it sit and warm up the engine before taking off? His recommendation of the fuel trims will help immensely.

 

[bmpalevich]

Welcome to the forum from Oregon.

Like @Fless said, how is it driven, altitude, brand and octane of fuel? Lots of short trips? Mostly highway? Does it sit and warm up the engine before taking off? His recommendation of the fuel trims will help immensely.

Always hwy driven at 65 mph or 70mph not many in town short trips never left idling I can get my short trim and long trim I'm

Welcome to the forum from Oregon.

Like @Fless said, how is it driven, altitude, brand and octane of fuel? Lots of short trips? Mostly highway? Does it sit and warm up the engine before taking off? His recommendation of the fuel trims will help immensely.

Thanks, well I am running regular fuel in my yukon 87 octane Arco blend and I've also tried shell gas and others nothing seems too improve my fuel mileage I have no check engine lights on I was thinking maybe it's the fuel pressure regulator? I see most people talking about black tail pipe meaning it's that? I can get my scanner and read the sts and lts and I'll upload them to the thread.

 

[bmpalevich]

Welcome to the forum from Oregon.

Like @Fless said, how is it driven, altitude, brand and octane of fuel? Lots of short trips? Mostly highway? Does it sit and warm up the engine before taking off? His recommendation of the fuel trims will help immensely.

I drive freeway miles mostly not really in town it's a freeway rig for me I don't take short trips as for warming up the thing before taking off sometimes I let it a lil bit but not even for 2 minutes then I take off and go on my way. I will try to get the fuel trims posted soon! Thanks

 

[smcnair]

Wait, you are only getting 150 miles to a tank? With a 26 gallon tank?

 

[Noggles]

I don't notice a difference in my 05 using 87 vs 89 for 91. Oddly I did in my old Silverado with the same drivetrain lol. When you did your plugs were any darker than the others? More fuel saturated than others? Maybe you have a leaky fuel injector? Does it feel down on power when wide open throttle? What temp does it run at when fully warmed up? Has it ever been tuned before that you are aware of? Any modifications that you know of?

 

[bmpalevich]

Wait, you are only getting 150 miles to a tank? With a 26 gallon tank?

Yes 150 miles then I'm on E.. sucks huh?

 

[bmpalevich]

I don't notice a difference in my 05 using 87 vs 89 for 91. Oddly I did in my old Silverado with the same drivetrain lol. When you did your plugs were any darker than the others? More fuel saturated than others? Maybe you have a leaky fuel injector? Does it feel down on power when wide open throttle? What temp does it run at when fully warmed up? Has it ever been tuned before that you are aware of? Any modifications that you know of?

No odd plug color they were fairly clean other than the plug end it was pretty warn that's normal nothing out of the ordinary it sits below 210 pretty normal for a 5.3 I haven't done any modification to this at all other than getting an e fan professionally installed

 

[TollKeeper]

Next time you have it hooked up to a scantool, check the coolant temps, from cold to 210. It should be a smooth, linear, movement until its warmed up. It almost sounds like its stuck in closed loop.

What brand O2 sensors? MAF?

 

[Fless]

Yes 150 miles then I'm on E.. sucks huh?

Back up for a sec. When it's on 'E' and you fill it up, how many gallons does it take?

EDIT: here's the EPA estimated mpg for regular gas:

 

[rockola1971]

Lets say you are actually only getting 150 miles per full tank for sake of argument. Theres only 2 places the gas is going. Into the engine or out on the ground. You need to inspect for leaks but a leak that bad I would suspect you could smell it pretty badly. Disconnect the battery for 5mins which will force a clear and recal of engine parameters related to fuel injection system. Have a look at your ignition advance values while engine running at idle, 1200rpm, 1700rpm.

 

[Mudsport96]

Two things to check. Coolant temp sensor like already stated. And the flex fuel ethanol content sensor which adjusts the fuel and spark for e85. If it is reading false percentages of ethanol it will be dumping fuel. Also it will crank up timing for the slower burnrate of e85, so running too long on 87 octane with a tune for 106 can kill pistons. You need to get a scan tool capable of reading the alcohol sensor on your rig ASAP, or if that sensor is bad you can kill the pistons.

 

[bmpalevich]

Who do I send an email to of my video of my scanner results?

 

[bmpalevich]

They are OEM ac Delco parts btw

 

[Mudsport96]

Who do I send an email to of my video of my scanner results?

If you can screenshot the codes just post a picture of them

 

[bmpalevich]

If you can screenshot the codes just post a picture of them

It's a scanner not an app

 

[OR VietVet]

You can also download to you tube and then post to here. I have only done that 1 time about 2 years ago. Forgot how but others will help.

 

[bmpalevich]

If you can screenshot the codes just post a picture of them

Shared album from Brandon 📸

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photos.app.goo.gl

 

[OR VietVet]

I am having a hard time reading the numbers and I know you are trying to give us info but perhaps a little digging is in order. This first video shows short term fuel trim good/switching. The long term fuel trim is rock steady and not switching. The numbers point to a rich condition caused by maybe a detected vacuum leak and the system is running rich to try and offset the problem: Running rich at all times trying to compensate for a perceived lean condition may be exactly what is going on with you, I will try to look at your video again:

More explanations:

More:

This is about no codes and no CEL fuel trim diagnosis: