ECU and gas mileage

[slow8033]

I have owned my GSX now for about a month. When I got it it was about 3/4 full of gas. On that gas tank I only got about 190 miles and I had to fill it a few days ago. This tank seems to be doing much better...I was about to go buy an o2 sensor to see if that helps out at all.

However here's my question, when I got the car, I cleaned out the engine bay. Unhooked the battery etc. This would have reset the ECU. Would I have been getting that crappy of mileage because of that? did the computer need to be "ON" for 50 miles or so until the fuel trims leveled out again?

Or should I just bite the bullet and get the o2?

 

[97-gst]

You just got the car so are you sure you haven't been "getting on it" pretty hard to see what it'll do?

 

[slow8033]

You just got the car so are you sure you haven't been "getting on it" pretty hard to see what it'll do?

HA, see that's initially what I thought too. I moved to this car from a GS. But then I got to thinking about it, and no not really. Its completely stock except for a K&N filter, and by no means a fast race car etc. I just have driven it back and forth to work, and twice to the grocery store. I'm not much of a "racer" really.

I haven't been driving this car any harder or differently than my last one.

When the turbo starts building up boost and pulling, I have usually just been shifting to the next gear...probably driving at 1/4 to 1/2 throttle.

 

[19Eclipse90]

On the same note as above, I wouldn't jump to conclusions about parts needing replacement based off of one tank of gas. To answer your question, no, it would not take the ECU 50 miles to "level out the fuel trims".

Also, as horrid as 190 miles out of one tank sounds, it is an inaccurate way of knowing what fuel economy you are actually getting. The tank is 16 gallons, so if you used all 16 gallons (which is doubtful), you do have issues. The correct way of determining fuel economy is to fill the tank completely, drive it (being certain to record the mileage), and eventually fill it up completely again. Divide the number of miles driven by the number of gallons used to fill up the tank the second time.

What type of driving have you been doing (i.e. city, highway, mix %city/%highway)? What reason do you have to believe the O2 sensor is bad? Does the car have any modifications?

Personally I would run a couple tanks of gas to get a good feeling for the car and how much fuel it uses before making hasty purchases.

 

[slow8033]

On the same note as above, I wouldn't jump to conclusions about parts needing replacement based off of one tank of gas. To answer your question, no, it would not take the ECU 50 miles to "level out the fuel trims".

Also, as horrid as 190 miles out of one tank sounds, it is an inaccurate way of knowing what fuel economy you are actually getting. The tank is 16 gallons, so if you used all 16 gallons (which is doubtful), you do have issues. The correct way of determining fuel economy is to fill the tank completely, drive it (being certain to record the mileage), and eventually fill it up completely again. Divide the number of miles driven by the number of gallons used to fill up the tank the second time.

What type of driving have you been doing (i.e. city, highway, mix %city/%highway)? What reason do you have to believe the O2 sensor is bad? Does the car have any modifications?

Personally I would run a couple tanks of gas to get a good feeling for the car and how much fuel it uses before making hasty purchases.

It has just been driven to and from work, and twice to the grocery store. All stock (the reason I bought it, its all stock). I picked it up from the original owner with 3/4 of a tank, and 70 miles on the trip odometer. I drove the car to and from work, till it was down to I would say an 8th of a tank. I filled it up and put in 14.1 gallons, the trip odometer said 193.7 at this time.

basic math = 13.737 etc etc... per gallon. I think this car should do better than that. I have searched gas mileage posts on here and other places and over 300 miles per a tank is not unheard of. I would settle for 250-275.

The reason I was going to replace the o2 sensor is it's a big cause in poor mileage, and the one in the car seems to be original. The car has 140,000 on it and a member here suggested replacing it if it hadn't been replaced before.

I was just making sure my unhooking of the battery for a few hours didnt do something i wasn't aware of.

 

[19Eclipse90]

The car should definitely do better than that.

That is impressive you were able to put in 14.1 gallons. The most I have EVER put in a DSM is 13.6. I have a hard time believing that you had an 1/8th of a tank left and were able to put in more than 12 gallons (not to mention the convenient mathematics there as 1/8 of a tank would be 2 gallons left in your 16 gallon tank), but maybe your fuel level indicating equipment is in tip-top shape.

Again, I'd run a couple more tanks through to see if I couldn't improve on the mileage a bit before buying parts, but again, that's what I would do. If you truly feel the O2 sensor is the problem, by all means, replace it.

 

[slow8033]

The car should definitely do better than that.

That is impressive you were able to put in 14.1 gallons. The most I have EVER put in a DSM is 13.6. I have a hard time believing that you had an 1/8th of a tank left and were able to put in more than 12 gallons

I use 1/8 of a tank loosly here, it was between 1/4 and empty...probably more on the empty side. But being a car I am unfamiliar with I didnt wanna push it into the light coming on. I used to drive my GS about 20-30 miles past when the light came on. But I knew that car pretty well...and knew I could get away with it. and fillups on that one were regularly 14 gallons +. (i do cram it in there, I dont live in oregon, I dont have to stop when the handle clicks off, I'm a top off whore). haha!