Arrg - what else can it be - v poor mpg 1.4 Auto 2004 44k

N

notagain

200 miles from a full tank...9 gallons or 22 mpg...I mean 22 mpg.

Checked engine management with scanner and live data - no faults, all readings fine o2 sensors working as per spec. At correct temp, both coolant and Cat, checked with laser thermometer. Replaced temp sensor and Thermostat as matter of course. Serviced - clean air and oil filters, oil clean. Air pressure sensor cleaned, seems to be reading ok ( could do with resistance readings to check). New plugs which showed over fuelling...so could be intake pressure but .am I correct that there is no maf sensor just the pressure sensor, get a good range of resistance from throttle body. Cam sensor says its happy...

Brakes and running gear all ok, no binds, auto box fine clean change up and down, overdrive fine, fluid fine nice and pink.

So what am i missing as this cannot go on, I have a landrover - it does 24 mpg round town.......

Any symptoms for a timing chain failure - cannot quite get my head around that as should throw up a lot of errors but....
 
notagain said:
200 miles from a full tank...9 gallons or 22 mpg...I mean 22 mpg.

Checked engine management with scanner and live data - no faults, all readings fine o2 sensors working as per spec. At correct temp, both coolant and Cat, checked with laser thermometer. Replaced temp sensor and Thermostat as matter of course. Serviced - clean air and oil filters, oil clean. Air pressure sensor cleaned, seems to be reading ok ( could do with resistance readings to check). New plugs which showed over fuelling...so could be intake pressure but .am I correct that there is no maf sensor just the pressure sensor, get a good range of resistance from throttle body. Cam sensor says its happy...

Brakes and running gear all ok, no binds, auto box fine clean change up and down, overdrive fine, fluid fine nice and pink.

So what am i missing as this cannot go on, I have a landrover - it does 24 mpg round town.......

Any symptoms for a timing chain failure - cannot quite get my head around that as should throw up a lot of errors but....
Click to expand...
what are your fuel trim values
 
Many Thx
short trim is bouncing between .08 and 4.7 % at idle 775 average is 2.3 long : flat at -7.8%

But revisited the cat as have a problem with a bouncing post cat o2 sensor ...the run I did at the weekend showed stable .75v today its .15 to .85v with a long wait at .280 volts at idle so I am begining to think that it might be partially blocked cat...

Having now grilled my mother in law whose car it is it seems that when she said it was serviced regularly she meant it was about 7 years ago, apparently according to my brother in law its a waste of money servicing them but she didn't want me to think he was a berk.
 
fuel trims are ok,
What is your down stream 02 sensor voltage with the engine hot at idle.
blocked cat is certainly a possibility.Easiest way to check it is to connect a vacuum gauge using the servo vacuum take off.Reading should be around twenty.
The other way is to take the front o2 sensor out and check for back pressure.Its quite easy to rig up a union to connect a pressure gauge.Should be no more than 3 psi
 
Right ho will give that a shot and will check temp of cat after a run tonight, thank you.
post o2 at idle its up and down 0.15v to 0.82v with periods stable at .280....
 
Oh this is madness....seems cat is fine, o2 sensors are fine, the only fault I can find is the temp sensor on the map is reading 28 degrees c according to my odbc scanner but gives resistance about 2.61 @14 deg c beginning to lose hope.
 
notagain said:
Hi , many thanks finally got a working gauge on the vacuum take off steady at 20....any ideas ?
Click to expand...
Your cats fine at 20 inches no blockage.With it being auto I would look at gear box issues.
Have a quick check of engine coolant temperature and IAT temperature on live data after an overnight stand comparing the readings with ambient
 
Will do thanks, Gearbox has a little jerk between 1 2 ...whilst its warming but settles down. Coolant seems fine, and temp sensor reads correct - put a laser thermo on the thermostat and checked the temp sender - within 2 degrees of each other..will check the iat tommorow....

Thank you
 
Checked IAT - showing 7 degrees for outside air temp of 6, tracked well on a drive - 1-2 degrees above air temp. However after a stop and restart, IAT showed 28 , air at 6..car ran ok ish but idled at 700rpm and was lumpy. Gave it a few miles and IAT was stuck north of 25 with air temp 6-7. So could be a faulty temp sensor, car came with a badly fouled air filter, might have scavanegd from the engine, I stripped the inlet down and cleaned it, replace the seals and plugs at the time....but the map sensor is a pricy thing to replace so any other checks ?

Gearbox - noticed that overdrive light fails to come on in drive, overdrive works but no light, light comes on when in park - don't know enough about the ecu to know if there is a feedback to ecu other than the selector switch.

Any help as ever received with thanks
 

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