how to know if your I-6 is running right ?

[paul2005tb]

I have noticed as long as I can remember that when on the HWY if I step on the gas to accelerate my TB will drop down to 2 or 3rd gear and rev at about 4000 RPM. I dont know if this is normal, can others weigh in please. Does your vehicle have power in 4th gear ? I get about 19mpg on the hwy so it cant be anything too serious but Id like to know what other vehicles have for power so I can compare.

 

[Sparky]

Probably isn't dropping to 2nd. First it drops out of TCC lock, then it'll downshift to 3rd. Can feel like 2 gear drops but really is not.

 

[HARDTRAILZ]

Seems correct

 

[Mounce]

 

[yonkster4g4]

My trailblazer does the same thing but my gas mileage is way worse and feels like it has no power. I cant figure out why. That's why I joined because I need help to figure this out.

 

[Lckent48]

19 mpg sounds a little low. I can cruise all day at 75 & get 22 mpg. Stop & go traffic, like metro Denver, 19 sounds about right.

 

[Sparky]

Depends on driving habits, traffic, gearing, and what your terrain is like. Also I think the OP is lifted now so that will affect it also.

 

[smokey262]

My 2004 gets about 19.7 on the hwy, which isn't bad according to this

https://www.fueleconomy.gov/feg/bymodel/2004_Chevrolet_TrailBlazer.shtml

As far as power goes, it has the highway gears so it doesn't exactly push you back in the seat

 

[Mounce]

19 mpg sounds a little low. I can cruise all day at 75 & get 22 mpg. Stop & go traffic, like metro Denver, 19 sounds about right.

19 sounds low? Higher than what most people report.

 

[paul2005tb]

Just to be clear:

1) my 19mpg number was my average before the lift.

Im still collecting data on the difference with the lift. But unless it costs me more than 3mpgs Im not going back

2) I have the 3.73 rear gear. I dont know if that is why I get a little lower than some of you.

3) Does gasoline vary much state to state? Im going to guess that it does not.

4) Im at 80k miles, I will be changing plugs for the first time this weekend.

 

[Blckshdw]

2) I have the 3.73 rear gear. I dont know if that is why I get a little lower than some of you.

^^^^ This is the cause right here. If you had 4.10 gears, your fuel economy would be even lower on the highway.

 

[Mike w]

I average 15 city 20 Hwy at 186k

 

[HARDTRAILZ]

Just to be clear:

3) Does gasoline vary much state to state? Im going to guess that it does not.

yes it does. The ethanol content can and it really really affects MPG. Corn should be eaten not in fuel.

 

[Tiggerr]

yes it does. The ethanol content can and it really really affects MPG. Corn should be eaten not in fuel.

Other additives too. That's one of the reasons prices vary so much state to state. Even from county to county. 50 states and probably 100 different gasolines.

 

[paul2005tb]

I average 15 city 20 Hwy at 186k

Do you have the 3.73 or the 3.42 rear gear?

 

[yonkster4g4]

I am only getting 14 mpg in my ltz. I found a vacuum leak the other day and fixed, it is a little better but still something is wrong.

It's not shifting as erratically as it was but still sluggish.

 

[Mike w]

Do you have the 3.73 or the 3.42 rear gear?

i have 3.42

 

[dkvasnicka]

19 mpg sounds a little low. I can cruise all day at 75 & get 22 mpg. Stop & go traffic, like metro Denver, 19 sounds about right.

What rear gear do you have? Last I checked it I was getting 22 mpg - but doing only 70 and with the A/C off (3.73 gear). Do you get this kind of mileage with A/C?
I'm talking about setting the cruise control to a speed and resetting the MPG display while driving. Also the 9-7X may have a few more lbs compared to the TB...

 

[paul2005tb]

Now that I have replaced my plugs and she is running much better I will make my first mpg calculation by next week. With the 3" lift my best hope is to be at 19mpg.

 

[yonkster4g4]

I changed the CPAS and my TB seems to run better but whenever I put the pedal to the floor or stills falls on its face and the LTFT goes to like -18%. Is that right?

 

[paul2005tb]

I changed the CPAS and my TB seems to run better but whenever I put the pedal to the floor or stills falls on its face and the LTFT goes to like -18%. Is that right?

did a google search and I cant find out what CPAS means ?

oh and what does LTFT mean ?

 

[Blckshdw]

did a google search and I cant find out what CPAS means ?

camshaft position actuator solenoid

 

[yonkster4g4]

LTFT is long term fuel trim

 

[Lckent48]

dkvasnika,

I'm running 3.42 gears. A/C on about 1/2 the time.

Tried to quote your post, but it just wouldn't work.

 

[paul2005tb]

3.73 rear gear and the G80 locker. The vehicle brand new gave me over 20mpgs hwy.


1) Review/background : With no lift, 85k miles with original old spark plugs, 19mpg (over a given commuter week with about 90% hwy miles).

2) Now : With 3/2 Markmc lift and new AC Delco Iridium spark plugs: 387 miles on 20.3 gallons= 19.0 mpgs, (same commuter week, about 90% hwy)

Just FYI, I was getting under 350 miles per tank in the interim between the lift and the spark plug replacement.

Caveat: I am a very tame driver, tend to accelerate gradually, and drive under 70mph.


Im very pleased !!... The elation that comes with a well maintained vehicle cant be over estimated.