Why is my 2004 EXT LT trailblazer burning too much gas.

Hello, How much of a change in MPG? Have you been experiencing bitter cold temps or seasonally cool temps (winter)? This can cause your MPG to drop especially if you drive shorter distances. It takes more fuel for a cold engine to run than a warm one & your engine management system works at peak performance after the oxygen sensors (in the exhaust) have reached temp....

Your spark plugs need changed. Once they get a larger gap it takes more gas to fire the cylinder. Dirty air filter and tire pressure will cause it too.

This has been going on since it was warm out. Tire pressure is fine. It is not that cold here. My spark plugs were checked and they are fine. A complete OEM diagnostics has been run and nothing can be determined that could be causing the drastic fuel consumption. It is getting around 11 to 12 mpg compared to 16+ in the city. Road driving hasn't changed that much.

Do you have 'check engine' or 'tailpipe' emissions testing in your state?

Also how long are you driving for and what are the air temps? Has low fuel economy persisted while experimenting with other fuel companies?

Winter gas. They put additives in it and it kills everyones fuel mileage.

I've been having the same issue. Dropped from 17 mpg to 10 mpg and I can't figure out why. No codes and no check engine light. Tire pressure is good. I've replaced the spark plugs, fuel filter, fuel pressure regulator, and o2 censor. Tried running 6 tanks of non ethonol fuel too. Nothing seems to help. I'm at a complete loss as to why the milage took such a hit. And it's getting 10 mpg all year long..winter, spring, summer, fall.

2005 Trailblaser with the same problem, runs and idles fine but millage took a dump. I used to get over 300 miles a tank now I get less than 150 miles a tank? Someone has to know what is going on?

I see no answers here and this hasn't been helpful at all... I'm getting hardly 10 mpg... Can anyone explain what's going on? I had a friend that had a similar size SUV of another maker (Pacifica) experiencing the same horrible gas mileage everyone was thinking transmission, tune-up whatever; however, they vehicle showed a code for the catalytic converter during the complete computer diagnostic test … Sure enough order the item had it installed ..WHAM-O… problem solved.. Does anyone know what solves this problem for the 2003 Trail Blazer 4.2ltr? Please help a single mother three kids and things are not going well and need the help seriously.

I have Trailblazer LT 2004, I have the same gas problem, and I have no idea what to do with it !! can anyone help plz.

I have a 2005 ext trailblazer and have never gotten less than 16.5 mpg city and no less than 21.3 on the highway loaded down. Every 6 months, I pull the throttle body completely off and clean it back to silver, I run a full k&n intake and euridium plugs gapped at .040 and only premium fuel. The new window sticker says 14 mpg city and 18 mpg highway this is why complaints of 12-15 mpg make no sense especially if proper matainance isnt done just saying

I have the samer problem with a 2008 TB. Cleaned a filthy Throttle Body and still a problem. Went to a muffler shop and he said the Cat Conv was at 700 degrees and normal should be around 350. I had them replace both of them today 8/18/2017. Filled the gas tank and waiting to see what happens. Wish me luck

New Cat didnt help at all. $750 down the drain

That would be because a cat running 700 degrees isn't that far fetched as mine runs 650 degrees and after routine maintenance including proper .045 plug gaps on uridium plugs, cleaning the 4" k&n filter and piping, the throttle body cleaned off the manifold and iac as well as tps cleaned and reassembled and lastly the map sensor and deleted the valve cover vent tub in favor of a similar stand alone breather much like what came in the cold air kit for my gs-r and my sr/t 4. The latest calculation is 19.1 mpg on ethanol free fuel on the street. We are taking a trip next weekend. The last trip in the dead of summer yielded 21.3 mpg on the highway on premium fuel. I'm expecting somewhere in the same neighborhood this trip. Please keep in mind that I have the rwd ext model. I have done the exact same procedure on a friend 4wd trailblazer ls swb and it only did 19 mpg on the hwy and 17 mpg on the street. The driver of this particular trailblazer loves higher rpm and likes to make 40mph-100mph pulls often so I'm not surprised. The difference in hearing is the ultimate deciding factor as obviously 80mph @ 1800 ish rpm is alot more efficient than the same 80mph @ 2500-3000 rpm.

This is simply a dirty fuel filter Incase no one has thought about it, a clogged fuel filter will cause worse gas mileage, and it's annoying seeing people take things like these over board and over look the damn fuel filter. Not more than $15 and it's an easy replacement.

I have tried new fuel filter new spark plugs and I'm getting the same gas mileage these people don't know what they're talking about

Walter, I have a 2005 trailblazer, with 4 wheel drive and extended cab. It is a great vehicle for many of the tasks that I have to accomplish but it too is beginning to suffer from poor gas mileage. I just marked your last post as useful because it gives me the insight that one has to approach this trailblazer low gas mileage issue on a system level. However, I am not that familiar with all the components that make up the system which you refer to using acronyms. Please help me know which system components need some attention. In the meantime I will also do some research that will help me better understand your advice. Thanks Richard

Ok, so I'm going to clairify a few things. Firstly thank you for your question Richard. So I read back over this thread and found references to the fuel filter. If a vehicle starts, idles and runs down the road and there are no performance issues, that in itself, the deletes the possibility of a fuel starvation issue which is created via a clogged fuel filter. When one cleans a throttle body that nas no mechanical operating devices ( for example, electronic throttle plate), then most efficient way of cleaning it is to indeed remove it from the intake manifold and then remove idle air control valve ( iac) and throttle position sensor (tps) in order to not only save the sensors from possible chemical damage but to get a complete clean of the throttle body itself and all ports. The point is to promote good air flow to get a complete burn of fuel in every revolution. The second point I need to make very clear is that you cannot just throw cheap copper or platnum plugs in the 4.2L i6 as the oem plugs are eurdium ( hotter burning than both other types) because you will not get a hot enough combustion to burn all the fuel in the cylinder. Vehicles that done have a hot enough spark will often have the smell of fuel at the tail pipe. Considering the i6 uses coil on plug design and not s distributor, this means you can not manually advance or retard ignition timing as you can on Toyotas i6 the 1jz and 2jz as well as Nissan's rb26. This is why air flow, proper spark and correct tire pressure will yield the best mpg. We also tend to read the results of others and expect the same when his 2 is also not possible for many reasons. The most notable being the habbits of the driver. What I mean by this is really simple. We all see unnessicary lane change and hard accelleration both from 80mph rolls on the highway and from a dig at red lights. It takes a lot more to excerate hard in any condition than to keep a steady mph( this is why the hey mpg is always way higher that he city mpg). Simple logic is the other side of the fence. The best example I can give for that come from my own vehicles. The ext trailblazer is in the neighborhood of 6500 lbs where as the dc2 Acura Integra with full interior is 2800lbs. It takes less to move the lighter vehicle. The Integra also as 2 less cylinders to dump fuel in at any given time so it will obviously comsume less fuel than the trailblazer at any given time under the exact same conditions be it down a 1/8 mile drag strip or down i95 at the same elevation and mph. Air density is also a factor as both my vehicles do much better mpg in the south than they do at even 2k above sea levelm if s map ( manifold air pressure) sensor detects less air volume, it will tell the computer to increase fuel flow to keep afr ( air to fuel ratio) within normal operation spec. Last thing on this I have is the use of cheap fuels. You will not get the same combustion quality from an 87 octane fuel with 20% corn (ethanol)/ gallon as you would with even 87 octane with no ethanol at all. It's combination of ethanol and heavy footed tendencies than cause poor fuel economy in most cars and lack of matainance beyond an oil change and doing even that with crap materials isn't really smart either. A realistic mpg expectation at sea level to about 1500ft elevation of premium fuel with matainance kept up with quality parts from personal experience with not only my own trailblazer, but several other customer owner envoys, accenders and trailblazers that 16-18 on the streets is damn good over the advertised 14 mpg and 19-22 on a good 100+ mile trip is also quite good when it really isn't saposed to get 18 mpg. Sorry I know this is long winded for sure but the last little thing I have on the topic is really this, do not purchase an SUV/pick up truck or anything for that matter that weighs over 5k lbs and expect to get in the 30mpg range. If you have an SUV and got it because of the seating, trade it for a mini van and get that 8th seat and low 20mpg on the streets. If your trailblazer is knocking on or has surpassed 200k and you have not done any of the factory matainance in the manual and use inferior parts, fuels and lubricants, expect the advertised fuel consumption and worst in higher elevations. I'm happy to provide a product list if anyone is interested.

I also need to add for those who have the trailblazer/envoys with the 5.3/5.7 multiple catylitic converter system, is a V8 that was GM designed for power and torque. That motor is only saposed to get 16mpg tops with either the 4l60 or 4l65 tranny so there is really nothing more you can do beyond actually either trading it for a rwd i6 or performing the swap and compensating the displacement difference with a small turbo kit to make the power back and still get the same mpg for that V8 power. As well as 4x4 vehicles are at least 1k lbs heavier for the front diff and transfer case. So there is only so much you're going to do in this instance. Like I said before. My buddy's swb i6 with 4wd can't produce more than 19 mpg on the highway where as my red i6 gets 21.3 and some trips, even better like yesterday's total 287 mile round trip to the beach which was accomplished in about 7/16 of a tank of 93 octane from absolute full.so a whole tank only getting 300 miles seems to me there's maybe an math issue considering the volume the trailblazer holds at 20 or so in the swb and my ext has a 23 gallon tank. Based on math that would actually mean 15 mpg which is still better than they were advertised just saying.

Just we need to go to closest junk yard and through this sh***y cars there

I faced the same problem, My suolotion was to the the fuel pressure regulator And the spark plugs. Jordan Baker

Air Intake Temperature Sensor