Pontiac GTO Forum banner

1 - 20 of 41 Posts

·
Registered
Joined
·
20 Posts
Discussion Starter #1
Hello All-

have to make this quick..

I have had my GTO for 2 weeks now. I am avg 12mi city and 16mi highway

I stay out of the throttle, trying to break the engine in nice and easy.

6 speed, Red w/moonroof, running 93oct dealership is clueless, I knew more about the car then they did.

Your Take?
 

·
Registered
Joined
·
26 Posts
Just took the family out for a nice Sunday dinner at a town 30 miles away. No stops. I live in wide open Texas country. With the cruise set at 72 it was showing 28 mpg. I get 20 or better @ 40 mph.in 4th in town. Somethings wrong man. You need to hook it up to a gizmo to let her tell you what's wrong.
 

·
Registered
Joined
·
77 Posts
Auto Mileage

At 400 miles and with the automatic, my average so far is 15.5 MPG. Being a new toy, I have put my foot into it way too many times.

It left the dealer with that average at 9 MPG. They must of rode her hard on those test drives.

I figure if I can average around 17 - 18 MPG after the engine breaks in, I will be happy as this is higher than my SUV used to get.
 

·
Registered
Joined
·
20 Posts
Discussion Starter #4
Mileage

Thanks Blue Goat. Were do I go, again the dealership is clueless, I'll try asking the mechanic there to check it out. I never would have purchased this vehicle knowing that this was the type of gas mileage. I know what it is rated for is off by a few miles but this is ridiculous

I love my ride though, man its nice.. My payments are 517mo for 5yrs Ouch!!!

Ill update you if I find out what’s going on.

Take care, and watch out for the smokies
 

·
Registered
Joined
·
6 Posts
My first two tanks were running 21.3 MPG, I too drive mostly on open highways and back roads, minimal stop and go driving.
 

·
Registered
Joined
·
17 Posts
1stGTO said:
Hello All-

have to make this quick..

I have had my GTO for 2 weeks now. I am avg 12mi city and 16mi highway

I stay out of the throttle, trying to break the engine in nice and easy.

6 speed, Red w/moonroof, running 93oct dealership is clueless, I knew more about the car then they did.

Your Take?
first i would wait until you have some more miles on it before you get to excited about mpg. i am sorry your talking to a guy whose commuter car is a F250 w V10 so 12 mpg sounds good to me. my gto is for week end and pleasure driving so i dont pay to much attn to milage. ;)
 

·
Registered
Joined
·
53 Posts
Don't be too hasty to try and calc mile per gallon. For the first 500 hundred miles or so, your engine breaking in by wearing hard metal components to the soft ones. During this time you have extra friction and your compression will be lower during the break in.

Many of the new computers have different programs that handle fuel and engine management systems. These programs will run different sub routines the more miles you put on. I think at about 2,000 miles they run the full normal programs (maybe someone else has more info on this)... this is to keep you from hurting your own car.

Also when you are checking to see what the average MPG is, make sure you are resetting the ave. It is an average over all miles driven to include creeping forward at traffic lights.
 

·
Registered
Joined
·
28 Posts
My average has been, 1st two tanks were around 18mpg, last tank was 21.3
This tank is still near 24 mpg. As long as someone doesnt want to go for a test ride it should stay there :D Dont forget to reset your avg mpg to 0 at each fillup. That will give you mpg for that tank. If not you will get a life time average.
Joe
 

·
Registered
Joined
·
2,473 Posts
Just finished my 500 mile break in period so I felt safe to take it really easy on the engine, just as an experiment. My 75-mile each way commute over the mountains to the high desert nets an average mpg of 19.1 mpg. I'm sure that will improve.

Oh well...I didn't buy it for its frugality!
 

·
Registered
Joined
·
98 Posts
1STGTO,
Something is wrong. ECMs learn very fast on new vehicles ( less than 50 to 75 miles depending on how you drive) Even though mileage should improve as an engine breaks in, yours is not running correctly if you are driving as you say. Where in the country do you live? Mountains or cold?? If you haven't set a check engine light, you might still have a sensor problem. Have the dealer, one that knows what they are doing, put a TECH II on it and look at the outputs from the sensors with the vehicle running. Does coolant and Intake air temp look like it should?? Those are the two most common that could cause it to run rich. ( or maybe never go closed loop) Also have them look at the TPS throttle position sensor both closed throttle and WOT.
Ask the dealer..also when they have a TECH II hooked up ask if it's closed Loop...What do the O2 sensor read?? They will find something if you are really just driving normally at 12 to 16. In a 6 speed thats too low..

Here's another way we might help you on this board. AFter the engine is fully warm.Go drive 55 MPH on Flat level pavement. 1st in 5th gear at 55mpg, then 6Th gear at 55 MPH at both speeds with a speady throttle note the INST FUEL ECONOMY on that screen in the dash. Post it here. Others can drive their 6 speeds at the same speed and gear and quickly tell how far OFF your's is from normal MGP....Just a thought.

How about someone else checking thier INST MPG screen at 55 in 5th and 6th gear???and posting results.
I love a science project.....
 

·
Registered
Joined
·
53 Posts
GTO TOO said:
1STGTO,
Have the dealer, one that knows what they are doing, put a TECH II on it and look at the outputs from the sensors with the vehicle running. Does coolant and Intake air temp look like it should?? Those are the two most common that could cause it to run rich. ( or maybe never go closed loop)
In his post he stated that he took it to the dealer... and they did not find anything. If any of what your decribing is happening, the GTO would have shot a number of codes out imediately... of course this is the first thing they would check.

Also have them look at the TPS throttle position sensor both closed throttle and WOT. Ask the dealer..also when they have a TECH II hooked up ask if it's closed Loop...What do the O2 sensor read??
I don't claim to know every thing about these cars... but just a simple question for you... ask if exactly what is a closed loop??

Also, when he asks the dealer what the O2 sensors read... What would be the range that would show a problem or not show a problem?

Thanks for these answers... don't send a Ranger into battle with a gun, but not any bullets.. :cheers
 

·
Registered
Joined
·
160 Posts
I just got back from a fishing trip to southern Georgia. It was a seven hour drive, all highway. My avg speed was 72.4mph and gas mileage is reading as 25mpg on this last fill-up. Watching the instant MPG while I was driving, it stayed right around the mid 20's while cruising, rising and dropping depending on the terrain, passing other veh's (which i did a lot!!LOL) etc.... My GTO is my everyday car, my 16 mile one-way commute to work being a combination of hwy and city driving, and I'm averaging about 17mpg.
 

·
Registered
Joined
·
109 Posts
Yeah, I also reccommend storming in to your local dealer and telling them how to work on your car. :confused
Be cool with you dealer, talk to the service manager and explain your concern to him (her) AFTER you have given the car time to fully seat the rings. If you go in there acting like an idiot, how willing do you think they will be to help you? Granted some dealers are pretty bad, but if you develop a good relationship with the service dpt. early on, I just may benefit you in the future. Most dealers have in house authority to perform "good will" warranty repair up to 60k IF they like ya. The guys in our service dpt. seems to bend over backwards (and forwards sometimes :eek: ) for good customers.
Just my opinion....B
 

·
Registered
Joined
·
159 Posts
:agree

There are three people you dont piss off in this world....

Waiters/chefs, caddies, and people that work on you car... all of these people can make your day go down hill really quick :shutme
 

·
Registered
Joined
·
98 Posts
First I did not say storm the dealership. Let's not twist what is said !!
1stGTO stated " dealership is clueless". I suggested several areas to look at and how to look at them. This site has been very calm but I sense some emotion in several of the newer posters. I would hope this site does not deteriorate to the level of most others. Rock you sound as if you work in a dealership. They work on cars they do not design and test them.
George, you are of the opinion that anything will set a code. Many things will, but some problems will NOT set a code. Sensors do not always just fail to one extereme or the other some can just output the wrong signal and cause issues. Again no offense but you are asking what closed loop is and yet have an opinion on how codes will set. I have some knowledge on how codes get set and how the system actully works. I was just trying to help. To answer your specific question on closed loop. That is one mode where feedback from the O2 sensors is used to maintain stoichometric Air/Fuel ratos. Stoich is where modern catylitic convertors have the best mutual efficencies for HC, CO, and NOX. While most engines run closed loop most of the time there are many operating conditions when an engine is NOT closed loop. ie. during warmup, and under some high load operating ranges. Watching both the front and rear O2 sensor outputs on a TECH II tool can help indicate what the problem might be. This engine seems to be running too rich for too long. If the dealership service is truely clueless they might be open to a few suggestions. That is all I tried to provide.
 

·
Registered
Joined
·
53 Posts
Well this time you DID provide (verus tried to). This answer is wwwaaayyy better than your first one. Thanks, I personally did not know how about the closed/loop durning warm up. It seems the computer is not really making so many adjustments until the engine is warmed up... at least in regeard to the O2 sensors. You mentionad the front and rear sensors, do you know where they are located on the GTO's exhaust system??

Is the GTO exhaust a duel exhaust with some kinda H pipe that connects to to balance the pressure... or is a single pipe with a single muffler that splits out to create 2 tail pipes??
 

·
Registered
Joined
·
109 Posts
OK, OK, so maybee "storming" was a little too dramatic. You understand what I mean though. It's just something I see happen from time to time here at the dealership. Some techs get real pissy when they think they are being questioned or challenged. These guys can be sort of sensitive that way.
I guess my hidden messsage in all of this is that you can catch more flys with honey.
 

·
Registered
Joined
·
109 Posts
George8211 said:
You mentionad the front and rear sensors, do you know where they are located on the GTO's exhaust system??

Is the GTO exhaust a duel exhaust with some kinda H pipe that connects to to balance the pressure... or is a single pipe with a single muffler that splits out to create 2 tail pipes??
When I looked under the car last night, I appears that the first cats are just inside the front tires along the firewall. The first O2 sensor is located just in front of them and then the second is under the middle of the car past the second cats. The car has an H pipe that from what I understand is blocked off for the GTO but not the Holden.
 
1 - 20 of 41 Posts
Top