rjjone2

As I have already complained about in other posts, my mpg tanked about 3 months ago when I had to get my engine wiring harness replaced. I wanted to start this thread to see who else on this forum had to get their wiring harness replaced and if their mpg was or is affected by it.

pyroman131

*Subscribed*

When I start removing my performance mods and inspect my xB, I'll post up my results here and see what happens.

TrevorS

iTrader: (1)

Darn dude, your RS 5 should be way past the serial number cutoff for the engine harness TSB. What's the story? (also, what is "tanked" and what does your dealer say.)

AAG

iTrader: (1)

Had mine replaced but didnt notice any difference. You sure its not because of the winter blend gas and colder weather which = lower mpg?

buickid

Let the ECU relearn the fuel trims etc. Then you'll see your MPG go back up. Whenever you disconnect the battery, the computer has to relearn everything.

rjjone2

How long does this take? I've been driving for 4 months since I had it replaced.

Could be I guess but we're talking a drop of 6-7 mpg here. Is that possible from just winter blend fuel?

It wasn't. I got the CEL light, traction control, and stability control lights all at once. Looked it up and saw the tsb. Took it to the dealer and they said that's what it was. I complained about my poor gas mileage then and they said it was cause of the bad harness. I have not talked to them about it since they replaced it.

AAG

iTrader: (1)

It's possible especially if you're riding on 19's.

buickid

Oh never mind. It should relearn within 100 miles of driving or so...

rjjone2

I'm biting the bullet and taking it in tomorrow. Last tank I averaged 20 mpg with some highway driving everyday and i just gassed it up and haven't seen over 18 yet.

When I called to make the appt. the service rep was like "Well low mpg is one of the hardest things to diagnose on a car."

So i figure that I'll fork over an hours worth of labor to them to just hear them say that they didn't find anything.

AAG

iTrader: (1)

How are you calculating your gas mileage? What does "some" hwy driving mean? How fast are you going on the hwy?

If there are no codes, you're wasting your time and money taking it to the dealer. Do you smell gas? Are you idling a lot? Have you kept up with the maintenance (fluids & filters)? Have you checked your tire pressure? There's alot of things that could cause the poor gas mileage.

You may need to get one of those things that plugs in to your obd2 port to see if your car is running rich. Running rich + cold weather + winter blend gas with 10% ethanol + heavy wheels I'm guessing are the main culprits.

rjjone2

For 4 months I was doing the ol' calculator method (number of miles driven/how many gallons i would fill up with). Then I started using my carputer and found that it was usually 1 or 2 miles higher than what I was calculating. So if my dash said 20mpg I was actually getting 19.

Some hwy means about 30 minutes a day at 65mph. But I live in a pretty rural area and don't go through many lights. Anyways when I went on a long trip I was averaging 23mpg hwy. In a large city I get 16 mpg.

There is not a CEL light but the ECU is always spitting out codes (pending). I believe I have smelled gas.

Everything is fresh and new (air filter, plugs, MAF cleaned, fluids). My tire pressure is exactly spec.

I do not have the obdII tool. I suspect I am running rich as well but why is the question. That's what I'm going to the dealer for. And my alloy wheels are lighter than stock by 7 lbs per wheel so if anything I should be getting better gas mileage than stock wheels. 19" alloy wheels weight less than stock steel wheels.

I used winter blend gasoline all last winter and did not notice this hit to my fuel economy.

AAG

iTrader: (1)

Maybe try swaping the ECU with another one. Ive seen a few on ebay and thats the only other thing I can think of. If you smell gas thats def a concern...

rjjone2

Yeah I am crazy enough to resort to something like this. I tend to let stuff like this really get to me. I would say that when I let my car idle for a long period of time, I can begin to smell gas inside the car. But its not often.

rjjone2

http://www.nytimes.com/2008/07/26/bu...26ethanol.html

"Some drivers think the change is notably greater. Chuck Mai, a vice president of AAA Oklahoma, reported that his organization has been getting calls from members blaming E10 for mileage drops of 8 to 20 percent.

Drivers in Tulsa, he said, are complaining to their local service stations , saying, “ ‘I used to get 28 mpg; last time around, I’m getting 25. What’s going on?’ ”"

So after taking it to the dealership, I was basically told that my xB is functioning perfectly normal and that its the gasoline. 10% ethanol. I've been reading up about it online. I don't think its a "winter blend" issue. I mentioned this to the dealer and they basically laughed at me. For those that have said "winter blend" can you elaborate?

CIONIDE

iTrader: (1)

http://ask.cars.com/2009/02/whats-th...y-cars-pe.html
http://blog.gasbuddy.com/posts/Winte...22955-413.aspx
http://www.theoildrum.com/story/2006/9/13/234043/431