[Doc Joe]

Hello Gents,

First a little back round about my wife's truck, 2009 Ext cab, 2X4, I4 with a 5 speed and is 100% stock and has just a click over 70K miles. I did change the plugs at 60K miles.

So last weekend I was rotating the tires and noticed that the tail pipe was real black as in Rich running conditions, was my first thought. Now this truck gets about 21 to 24 mpg city and Hi-way and I still feel it should get much better than that. It's not throwing and codes. Just wondering if I have an issue and I don't know what it is or do I have a O2 sensor about to go out or needs replaced??

Thanks for your help...

Doc.

 

[Joe canyon]

I'd change the o2 if it has more than 45k on it. I picked up some MPG after doing mine never had a soot problem but that could be the o2 on yours. What plugs did you put in it?

 

[Doc Joe]

NGK IR plugs... Was asking a friend and he thought it might be my temp sensor??

Doc.

 

[Joe canyon]

Yea. Which temp sensor are you thinking it could be?

 

[Doc Joe]

Yea. Which temp sensor are you thinking it could be?

Joe I have no idea, I was just thinking out loud and hoping this might lead me to a place where to start looking??

Doc.

 

[cart7881]

Lower than normal engine operating temperatures can cause issues with mileage. You should, however, have a corresponding drop on the temperature indicator in the instrument cluster. If the temperature indicator stays around the 1/4 mark, that would be a clue. On these trucks the most common cause of this issue is a defective thermostat.

 

[LLV.MA5]

My 2.9 used to get about the same mileage as yours. I was pretty frustrated with it for a while. I even took it back to the dealer I bought it from and had them scan it to see if anything was wrong. They said everything looked normal. Then I started replacing sensors and plugs and cleaning things, but nothing helped. Finally I had the computer tuned by someone who knew what they were doing and my mileage jumped about 4mpg.

I'd recommend you save yourself the hassle of replacing a bunch of random sensors and just get a good tune. It makes a huge difference.

 

[Joe canyon]

If the truck is running good and you have no cel it very well may just be the factory tune as that is what GM has established as their best of normal operating parameters. The only sensor I'd throw at the truck with no cel is the o2 for MPG gain. Also we are now in the cold weather season and MPG will go down as compared to warm conditions.

 

[Doc Joe]

Thanks for all your help guys, glad to know I am not the only one who is or has had issues with MPG in the 2.9 trucks...

I have a friend of mine who owns a dino shop, may have to stop in and have him look at it??

Doc.

 

[08Canyon]

A tail pipe isn't hot enough to burn off the carbon.
My tailpipe is sooty in appearance. Are they ever perfectly clean? I don't think any of mine have been??

 

[Doc Joe]

A tail pipe isn't hot enough to burn off the carbon.
My tailpipe is sooty in appearance. Are they ever perfectly clean? I don't think any of mine have been??

I have owed my share of cars and trucks and every time I have had a tailpipe look this black means something is wrong some where in the system.

This is why I asked on here to see if anyone had any idea what might be wrong. Now I am going to have the trucks ECU tuned and hopeful that is solves the problem.

Doc.

 

[peter04]

I have a stock thermostat on my 04 i5 and my ultra gauge says it's 176 operating temp. Sometimes on the highway downhill it will throw a pending code for too cold. My question based on the above would be is 5 or 10 degrees really enough to cause a noticeable difference in MPG or performance if I'm daily driving?