My ecconomical I6 gone? Why?

Gianz · 05-02-2007, 12:14 PM

Hi all,

Over the last few months my au xr6 has been drinking like a pig and i cant work out why...

here is a bit of background....

I go away almost every weekend (travelling over 850kms a week)
I service my car every 5000kms on the dot (using only the best oils and lube)
up untill about a couple of months ago i was getting 750km to 900km to a tank on the highway and now ill be lucky to even get 600km. (yes i do realise i have been using the air con)

My girl has done 130,000 Kms and still running better than ever.
equipped with full exhaust system, unichip...nothing should be causing this...

its driving me crazy.. what could it be???

Quicklier · 05-02-2007, 12:24 PM

O2 sensor fouling?
What's the power like?

**Mechan1k** · 05-02-2007, 12:54 PM

Is the car running cooler than normal ... might be a thermostat staying open at all times ... that's another thing that I can think of.

Other than that ... as Quicklier mentioned ... O2 sensor fouling .... may as well replace it anyway and see how it goes.

Then do an ECU reset (will take a little while after the reset for it to be running at it's optimum again as the ECU relearns.)

Gianz · 05-02-2007, 01:01 PM

yeah, i was suspect about the possibilities of it being the O2 sensor..

probably be best replacing it as sujested.. thanks guys.

apart from that i have reset the ecu, but no effect..... and as for the power, its never been better...

XR Rob · 05-02-2007, 01:05 PM

Wow, you were getting great fuel economy.

I'm getting nothing like that in city driving with the a/c on. What should I be getting???

Chrispy · 05-02-2007, 02:07 PM

Are you using good fuel, from a high turn over servo?
Chrispy

Gianz · 05-02-2007, 02:28 PM

Quote:

Originally Posted by Chrispy

Are you using good fuel, from a high turn over servo?
Chrispy

Yes! I always use good fuel......ive seen far too many engines ruined from bad fuel....none of them being mine thank god...!

JC · 05-02-2007, 03:39 PM

Quote:

Originally Posted by XR Rob

Wow, you were getting great fuel economy.

I'm getting nothing like that in city driving with the a/c on. What should I be getting???

You should get between 400 and 500kms per tank city driving. 400 if it's lots of stop start, up to 500 if you get some nice cruising at 60 or 80. On the highway (say Canberra to Melbourne) 700+km is easily achievable - I've done KalKallow (sp?) to Yass on a tank with DTE still showing 100km. 800+ would have to be on constant 100km/h with little to no hills.

As for Gian' problem - it is definitely a mixture issue, and the 3 major things that affect mixture are engine temp, O2 sensor and MAP sensor, as well as ECU/Chip settings. I wouldn't rule out the possibility that your unicrap has sh@t itself, but before going there, get a new O2 sensor (approx $80 off ebay for a genuine Bosch one) and fit it (I got instant 50km+ arond town improvement). I would also also replace the thermostat as well - for $30 or so it's extra insurance and after 100,000km+, it's worth replacing these things as preventative maintenance.

XR Rob · 05-02-2007, 03:42 PM

Wow, so that's some variation there. Thanks for that. I reckon this tank of petrol will yield about 450km, but a lot of it has been stop-start and I've been running the a/c most of the time, too. OK, so at least I'm in the ballpark here. Thanks.

Tech Trainer · 05-02-2007, 07:33 PM

What fuel are you using? Standard or high octane? Is your XR6 a VCT?

XR Rob · 05-02-2007, 07:54 PM

Mine is a VCT and that first tank I put in was high octane.

The Monty · 05-02-2007, 08:26 PM

Have you changed or washed your air fliter lately. I was chewing loads of fuel, cleaned my K&N filter and is now back to 500-700 a tank city and highway driving.

GK · 05-02-2007, 08:38 PM

Quote:

Originally Posted by XR Rob

Wow, you were getting great fuel economy.

I'm getting nothing like that in city driving with the a/c on. What should I be getting???

Rob, his figures were for the highway though!

GK

Gianz · 06-02-2007, 08:19 AM

As for Gian' problem - it is definitely a mixture issue, and the 3 major things that affect mixture are engine temp, O2 sensor and MAP sensor, as well as ECU/Chip settings. I wouldn't rule out the possibility that your unicrap has sh@t itself, but before going there, get a new O2 sensor (approx $80 off ebay for a genuine Bosch one) and fit it (I got instant 50km+ arond town improvement). I would also also replace the thermostat as well - for $30 or so it's extra insurance and after 100,000km+, it's worth replacing these things as preventative maintenance.[/QUOTE]

Thanks JC.
Here is just a little to think about..
1. i recently replaced the radiator and thermostat. in doing so i had a few choices and went for a cooler thermostat and an upgrade radiator. the car does run cooler but by cooler its still within the normal range, so maybe i should be using the hotter thermostat?

2. i wouldnt rule out the posibility of my unchip having sh#t itself either. there are days where i can tell (sniff sniff) my mixture is good and then days when its absolutely way out.. (screeeeams for edit)

so to my conclusion id say i have a few things to blame and need to be sorted...ahhh $$$$...but we all love it right...?

XR Rob · 06-02-2007, 09:06 AM

Quote:

Originally Posted by GK

Rob, his figures were for the highway though!

Yes,I know, that's why I was curious what city driving should deliver me.

I didn't expect it to be as little as half, which is why I asked.

LOWAU · 06-02-2007, 11:40 AM

Put a bottle of injector cleaner in your tank, see how that goes.

I put one in at every 2nd oil change or 10,000 kms.