Poor fuel economy?

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shaun16, Mar 8, 3:42am
91 sr20de primera. Averaging 400km for 45 litres. mostly town driving but even when doing more open road i hardly get any extra k's per tank. all this done recently - oil and filter, air filter, fuel filter, spark plugs, cleaned throttle body, cleaned air flow meter and replaced oxygen sensor. made no noticeable difference. any suggestions!

shaun16, Mar 8, 3:44am
and i had the cat cut out recently as i thought it may be blocked. cars done 220,000 k's

intrade, Mar 8, 3:48am
what fuel do you run on it! 91 !

shaun16, Mar 8, 3:50am
yep has about 34 in the tyres and i use 95, but probably do have a reasoniable heavy foot.
was wondering if it needs a tune up as the exhaust smells quite strong like almost unburnt fuel! smelt like that before removing the cat but probably smells a bit stronger now

shaun16, Mar 8, 3:52am
my back tyres are slightly smaller than the front, but even before i had them replaced i wasnt getting any better mileage

intrade, Mar 8, 4:02am
well get a diagnostic cable and find what is going wrong.
i got one of tradme from these crowd works mint with software dealer had listings on here but cant see any right now.
http://www.blazt.biz/products/cable.php

intrade, Mar 8, 4:07am
shows you all its awsom even injector currents on display temp sender you name it.
http://www.youtube.com/watch!v=aGX1NqqAnjs

mr_lovebug, Mar 8, 4:07am
Not read whole thread.

My question is,does the have a stanard exhust system!
If the system been changed the car MIGHT be "limp home mode"which means, that is pouring large amounts of gas into the motor & the air/gas mix is all WRONG!

Often caused when the Cat convertor is removed!

shaun16, Mar 8, 4:11am
it has the standard exhaust except no cat. the oxygen sensor is near the front of the car not in/near the cat. and even before the cat was removed it was getting the same fuel economy. i only removed the cat thinking it may help a bit

mr_lovebug, Mar 8, 4:15am
You might of had a bad sensor & that might of triped the "limp home mode",was looking at removing my cat convertor in my car, was told NOT to as it would then waste gas in LHM.

I wonder if you took the car to place pit stop & get them to check or fool the sensor you might get the car out LHM.

It's something to look into.

mr_lovebug, Mar 8, 4:36am

1fordluva, Mar 8, 4:43am
First thing to check when constantly doing the around town driving is the simple stuff first.
Air element or filter,is a standard one!
If it is, an educated guess is its as black as the ace of spades,so given time its rooted the plugs too,due to getting less air and more fuel.
If they are mint then 02 sensor.
My p10 primera averages 300km to half a tank with mixed driving.

shaun16, Mar 8, 5:18am
air filter is less than 3 months old and looks reasoniably clean and dust/dirt free. sparkplugs are probably a year old but checked them all the other day and all were clean looking.
02 sensor replaced approx 6 months ago with a proper matching nissan one i got off trademe

edangus, Mar 8, 5:28am
gummied up injectors!

1fordluva, Mar 8, 5:30am
Check codes for ecu,as above someone posted it could be in limp mode.

shaun16, Mar 8, 5:32am
ok thanks for all the help people. some good suggestions to try

mr_lovebug, Mar 8, 5:42am

franc123, Mar 8, 5:42am
I'm surprised its taken 20 posts to suggest the obvious.Is the engine at operating temperature, ie the thermostat is OK and is the coolant temp sensor giving the right readings!Both of these can be fuel wasters big time and quite common on 90's era Nissans.

1fordluva, Mar 8, 5:44am
Absolutely correct,dam I just did that not long ago.
My mind is getting old and forgeting things.

shaun16, Mar 8, 6:26am
where would i find the coolant temp sensor please! it gets to operating temperature ok and the thermostat and radiator and antifreeze were replaced approx 18 months ago as the radiator sprung a leak.

clark20, Mar 8, 8:24am
Yep, I'm sure if was me driving I would be happy with 11L/100km around town

1fordluva, Mar 8, 8:25am
Yeah fish but you looked proffesional with that black box mate ha ha

shaun16, Mar 9, 3:59am
ok just checked the fault codes and it came back with 34 which is apparently the knock sensor! anyone know if this would cause poor economy and have any idea what it may cost to replace! apparently they are usually situated in an awkard place so labour can cost a bit.

musikcrazee, Mar 9, 4:12am
my car a 3sfe auto corona is a pig around town - 13l/100km or more, but will do 7s on the open road

1fordluva, Mar 9, 4:56am
Knock sensor,will push car into limp mode.
However mellissa2000 had a primera do this a while back,ecu was shagged.