AU1 fuel consumption

[titan 4380]

I have a 1998 AU1 Fairmont with the 4.0l 6 cylinder. I am the second owner and I know for a fact that the car has been very well serviced all of its life and has spent most of its 300,000 km life on highway cycle. Since owning it I have driven it like an old fart and drive rurally at no faster than 80 kmph and 100 when I am on the highway. I run the car on 98RON fuel, but cannot seem to get any better economy than 11.3 L/100km. This seems to be absurdly high for a car that has been treated like a baby all of its life. Even with the ECON mode selected, the car does not show an improvement in economy. The car starts and runs like a Swiss watch except for in cold weather where the car will start ok, but then stall even though a second start will fix the problem. Any clues why I am getting such rotten fuel economy?

[PG2]

Fuel regulator.

You can replace them easy enough but you can sometimes get away with giving it a clean.

[titan 4380]

Originally Posted by PG2

Fuel regulator.

You can replace them easy enough but you can sometimes get away with giving it a clean.

Can you give me an idea why it would cause this problem?

[PG2]

Originally Posted by titan 4380

Can you give me an idea why it would cause this problem?

Yep, no dramas.

The reg can get clogged up for any number of reasons such as dirty fuel or even just over a period of time.

If the reg gets clogged up it can cause the car to run rich. Sometimes when they run rich there are no other telltale signs other than high fuel consumption.

[titan 4380]

Originally Posted by PG2

Yep, no dramas.

The reg can get clogged up for any number of reasons such as dirty fuel or even just over a period of time.

If the reg gets clogged up it can cause the car to run rich. Sometimes when they run rich there are no other telltale signs other than high fuel consumption.

Thanks for the response. Please indulge me for a moment while I try to understand the problem. Doesnt the car ECU control the injector timing to set lean or rich setting based off the O2 sensor reading.I thought the fuel pressure regulator controlled the injector rail pressure and not the injector timing. Please correct me if I have this wrong.

[PG2]

I wasn't referring to whether it is running lean or rich. You said that you are getting poor fuel economy and it is hard to start of a morning.

That would suggest to me that it is the fuel regulator. I had a very similar problem to yours (and still do to an extent) but once I cleaned the reg it improved out of sight. I suggested the fuel regulator as it is the cheapest thing to look at first.

Your two problems could either be caused by the same problem or completely separate problems. It very well may not be the fuel regulator and could be a number of things, such as;

• coil pack
• leads
• spark plugs
• O2 sensor
• clogged fuel filter
• Fuel pump
• Fuel pump recently changed and the fuel lines put back on in the wrong order

The above is not an exhaustive list.

You could always run a scan over it to check to see if it could be something else. Sometimes scans though do not pick up the actual problem though.

Failing that, spend the money and buy an O2 sensor and see if that works.

[titan 4380]

Originally Posted by PG2

I wasn't referring to whether it is running lean or rich. You said that you are getting poor fuel economy and it is hard to start of a morning.

That would suggest to me that it is the fuel regulator. I had a very similar problem to yours (and still do to an extent) but once I cleaned the reg it improved out of sight. I suggested the fuel regulator as it is the cheapest thing to look at first.

Your two problems could either be caused by the same problem or completely separate problems. It very well may not be the fuel regulator and could be a number of things, such as;

• coil pack
• leads
• spark plugs
• O2 sensor
• clogged fuel filter
• Fuel pump
• Fuel pump recently changed and the fuel lines put back on in the wrong order

The above is not an exhaustive list.

You could always run a scan over it to check to see if it could be something else. Sometimes scans though do not pick up the actual problem though.

Failing that, spend the money and buy an O2 sensor and see if that works.

Once again, thanks for your input. I was leaning toward either O2 sensor or MAF sensor. Looking at the cars servicing history, the O2 sensor was replaced about a year ago, but I suppose that its possible for anything to fail prematurely. While the car starts easily, in cold weather it starts then dies. I had this problem on my beamer and it turned out to be the fuel lines reconnected in reverse thanks to yours truly.