Poor fuel economy [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: Poor fuel economy


tony0452
01-05-2011, 11:04 PM
Hello All & Happy New Year!

Would like to pass this on to all those experiencing poor MPG. My 03 TB LTZ was sucking fuel like a thirsty pig, worse gas mileage than a TB SS. I changed the exhaust to a Gibson stainless with no luck (truck sounds good though). Stopped by local dealer to discuss problems and got the standard line of "no codes, not anything I can do for you with no other suggestions). OK, time to solve problems myself.
Now, everything was running fine except for the MPG, duh what could it be? Every once in awhile when idling I would hear a slight ticking and at start-up the engine would "roar" for a moment a little more than I remember. Started searching the internet with the symptoms I had at hand and came up with the fan clutch being shot. Keep in mind, I DID MENTION THESE CONDITIONS AT LOCAL DEALERSHIP and of course drew a dumb look from the service guy.
Truck will be out of warranty 01/17/2011 so I was in a hurry to get this fixed under warranty. The fan clutch in itself is EXPENSIVE (OEM Delphi/Delco) so just as insurance before I took the truck to dealer I bought one just in case I was told the clutch was not bad. Best price and I mean the best price was at AMAZON.com, OEM fan clutch for $218.00 free shipping. Amazon beat Rock Auto. com price by about $50.00 but trust me either price is a GOOD one but go with AMAZON first.
Dealership agreed with my diagnosis and changed the clutch fan under warranty so it cost me the $100.00 deductible. So far, two days later the MPG is MUCH better. Now, for those of you members who will have to do this yourself you will also absolutely need a fan clutch tool to hold the water pump pulley as you screw off the clutch. The tool can also be found on AMAZON for $37.00. You will need this tool in your box anyway if you ever have to replace the water pump (mine on order).
If your MPG is horrible on your Envoy or TB the clutch could be bad and even if you have to do the job yourself not that bad but you ABSOLUTELY need the tool I spoke of.
These clutch fans are not simple units as there is a thermal connector on the front that is plugged into the trucks computer to turn it on. Remember, replace with only a OEM part otherwise there could be some re-programming involved. Hope this helps.
Have more news to share later, 33 year GM employee.

envisionelec
01-05-2011, 11:21 PM
Hello All & Happy New Year!

Would like to pass this on to all those experiencing poor MPG. My 03 TB LTZ was sucking fuel like a thirsty pig, worse gas mileage than a TB SS. I changed the exhaust to a Gibson stainless with no luck (truck sounds good though). Stopped by local dealer to discuss problems and got the standard line of "no codes, not anything I can do for you with no other suggestions). OK, time to solve problems myself.
Now, everything was running fine except for the MPG, duh what could it be? Every once in awhile when idling I would hear a slight ticking and at start-up the engine would "roar" for a moment a little more than I remember. Started searching the internet with the symptoms I had at hand and came up with the fan clutch being shot. Keep in mind, I DID MENTION THESE CONDITIONS AT LOCAL DEALERSHIP and of course drew a dumb look from the service guy.
Truck will be out of warranty 01/17/2011 so I was in a hurry to get this fixed under warranty. The fan clutch in itself is EXPENSIVE (OEM Delphi/Delco) so just as insurance before I took the truck to dealer I bought one just in case I was told the clutch was not bad. Best price and I mean the best price was at AMAZON.com, OEM fan clutch for $218.00 free shipping. Amazon beat Rock Auto. com price by about $50.00 but trust me either price is a GOOD one but go with AMAZON first.
Dealership agreed with my diagnosis and changed the clutch fan under warranty so it cost me the $100.00 deductible. So far, two days later the MPG is MUCH better. Now, for those of you members who will have to do this yourself you will also absolutely need a fan clutch tool to hold the water pump pulley as you screw off the clutch. The tool can also be found on AMAZON for $37.00. You will need this tool in your box anyway if you ever have to replace the water pump (mine on order).
If your MPG is horrible on your Envoy or TB the clutch could be bad and even if you have to do the job yourself not that bad but you ABSOLUTELY need the tool I spoke of.
These clutch fans are not simple units as there is a thermal connector on the front that is plugged into the trucks computer to turn it on. Remember, replace with only a OEM part otherwise there could be some re-programming involved. Hope this helps.
Have more news to share later, 33 year GM employee.

Thank you for sharing your experience. I'd nearly exhausted ideas for my crappy mileage (O2, exhaust cam actuator, throttle body clean) and myriad other rule-outs. My clutch does tick or roar sometimes....I'll try it next.

deronh2002
01-10-2011, 12:25 PM
Typically, what would you check to see if your fan clutch is bad? I am getting around 11.7 MPG all the time...

tony0452
01-10-2011, 04:42 PM
Hello:

Hello, Happy New Year! Typically, you will hear a ticking at idle speed and when you first crank it up the engine will roar more so than usual. My 03 TB LTZ was experiencing the same awful mileage below 12 MPG no codes. The clutch fan is controlled by the PCM (power control module ) and when engaged all the time (bad) creates a drag on the motor and MPG goes south.

I hope this helps you, mine seems to be better as I do not see the gas gauge move as much. Heck I know it is better and next is a cold air intake to get rid of that restrictive box in the right hand corner that houses the air filter.

As I wrote before try Amazon (best price) or Rock auto. com for the clutch as this thing is expensive . Mine was $218.00 at Amazon and Rock had it for $262.00 and get only A/C Delco or Delphi replacement.

In the end this cannot not hurt and do not forget to check the overall health of the water pump and if in doubt just go ahead and change it as after the fan is off you are half way there. Also not a bad idea to change the thermostat too when everything is drained. Use Dex Cool (orange or Prestone brand that mixes with any color antifreeze. I never buy diluted mix or use water.

Hope this helps, let me know. Good luck!

Tony0452

Loverotties
01-10-2011, 05:03 PM
Changed it this last summer with no difference in MPG.

tony0452
01-10-2011, 08:35 PM
Hello:

Sorry about that. Mine has improved but not dramatically, I did put a Gibson exhaust on the truck. My 03 LTZ has only about 33K on it, how reliable has your truck been since it is first year model. My wife has an 02 Blazer and although smaller it is more capable in bad weather. The TB is scary fast at times and you do have to be careful with it. The darn horsepower than my 87 Vette (248).

The gas mileage on the Vette is unbelievable, you would not imagine the MPG it gets so whats up with the TB.

Regards,

tony0452

NYDeer
03-09-2011, 12:21 PM
I was getting 10 city/14 hway mpg. I already run synthetic fluids. I used Seafoam in the tank, went to stock sized General HTSs, replaced the plugs with Delco Iridium's, cleaned the throttle body. We just took a trip, and got @15.5 mpg for daily driving. Going up, at 75-80, it was @17mpg. Coming down, at 60-65, @18.5. The truck was loaded down too, so empty, I expect better numbers..

deronh2002
03-09-2011, 01:09 PM
I ran two containers of Techron through my fuel system and went from 11.7 mpg to 15 mpg. Also bought a K&N filter. Don't think the filter has really increased the MPG since I was getting 15 mpg before I installed the filter. Changing the Spark plugs will be next.

envisionelec
03-09-2011, 04:53 PM
My fix was to replace the CAM sensor. After doing this, I started to get rough idle and codes P0014/P1345 after driving at freeway speeds for more than 20 minutes.

I changed the spark plugs (Delco) and all codes disappeared. Gas mileage is 15 City/19-20 Highway. My Bravada has 207k miles.

DragonNote
03-15-2011, 12:57 AM
Had this exact discussion with a local mechanic (and friend) that I know an he said that the gas is more ethanol heavy and could be partially to blame. Around here (upstate NY) all you can get is eGas. :-( I am getting 12.5 avg.

shelbygoat
03-15-2011, 10:28 AM
Had this exact discussion with a local mechanic (and friend) that I know an he said that the gas is more ethanol heavy and could be partially to blame. Around here (upstate NY) all you can get is eGas. :-( I am getting 12.5 avg.

17 around town...pcmforless tune. do it.

Audiojunky
03-15-2011, 01:08 PM
Just did the spark plugs and cleaned the throttle body on mine last night. First thing I noticed was that my exhaust was quieter. I drove it for about twenty miles on the highway and in town and noticed a big difference in acceleration. As soon as I floor it, it goes. No more hesitation. I have a tune installed from Wait4Me and an Airaid CAI. I have a high flow muffler, but don't ask me the brand, because I have no idea. Now, if I can keep my foot lighter on the throttle, I should see my numbers go up.

Also one thing to mention, I upper the tire pressure to 45psi. All of my tires were around 30psi. Max psi on the tire is 50.

DragonNote
03-15-2011, 01:23 PM
Just did the spark plugs and cleaned the throttle body on mine last night. First thing I noticed was that my exhaust was quieter. I drove it for about twenty miles on the highway and in town and noticed a big difference in acceleration. As soon as I floor it, it goes. No more hesitation. I have a tune installed from Wait4Me and an Airaid CAI. I have a high flow muffler, but don't ask me the brand, because I have no idea. Now, if I can keep my foot lighter on the throttle, I should see my numbers go up.

Also one thing to mention, I upper the tire pressure to 45psi. All of my tires were around 30psi. Max psi on the tire is 50.

Cool, I did my plugs and throttle body last summer. I saw quite an improvement as well on my 2002 (100,000miles) The mileage has just been as of late. I have a bad front/passenger wheel bearing and my tires are at 40psi (rated at max 44) so I am hoping that has something to do with the 4-5 mpg I am off from most. I was using 93oct only for a while and did see an increase in my mileage but that seems to have gone away with the bearing..

mitsusport2000
04-10-2011, 08:50 PM
I've noticed my MPG had decreased and the "infamous ticking noise" that typically appears when i'm idle or the A/C is running. I saw that most people said the fan clutch solves that problem. I'm a women and don't foresee tackling that project myself so I will be "paying the piper". I also saw that some people said switching to synthetic oil may help as well? Which is better or should I try them all?

I have an 03 Trailblazer with about 147,000 miles on it and thought maybe I needed a good tuneup to improve my MPG. (I've had some of those maintenance 30, 60, or 90K maintenance things done but I don't recall switching out my spark plugs or fuel filter.) I haven't had any major problems with my Trailblazer, which is a blessing but I typically try to take care of symptoms before they become major problems!!

Thanks!!

Loverotties
04-10-2011, 09:21 PM
I've noticed my MPG had decreased and the "infamous ticking noise" that typically appears when i'm idle or the A/C is running. I saw that most people said the fan clutch solves that problem. I'm a women and don't foresee tackling that project myself so I will be "paying the piper". I also saw that some people said switching to synthetic oil may help as well? Which is better or should I try them all?

I have an 03 Trailblazer with about 147,000 miles on it and thought maybe I needed a good tuneup to improve my MPG. (I've had some of those maintenance 30, 60, or 90K maintenance things done but I don't recall switching out my spark plugs or fuel filter.) I haven't had any major problems with my Trailblazer, which is a blessing but I typically try to take care of symptoms before they become major problems!!

Thanks!!There's a lot of thing that could help.Plugs,front O2 sensor,Air filter,fuel filter,thermostat,synthetic oil and seafoaming and cleaning Throttle body.

Macatowa
04-10-2011, 09:38 PM
Mine is not good right now, 181,000 miles; however mine is the fuel pump leaking and it is spraying fuel on the top and above the tank. The mpg for urban driving only is 13-14 and it should be 16-18. Eight salt bath winters does a number on these rigs and i need to drop the tank and replace the fuel pump. I
don't qualify for the bulletin fix but I may call to see if they might given that i have bought two trucks from them.