VR Senator problems 22L/100km :|

[mwemy]

ok, lets start off with saying this car uses a HUGE amount of fuel and is slower than my friends ex-chaser VR,
im using 22L / 100km, and it has a rough idle when first started (sounds quite lumpy and mean for about 5 seconds)

Ive checked for inlet manifold leaks, no codes came up, has standard memcal in it, plugs are new, leads are new, coil new, i thought the throttle may be sticking, but the throttle body all the way into the manifold is SPOTLESS clean, wich surprised me a bit O.o hence why i checked for inlet manifold leaks, it has a higher stall in it (2500 i think) i was thinking of cleaning out the IAC but that surely doesnt cause 22l/100, my temp guage normally sits at 1/4 bar and only ever gets to 1/2 when it gets a bit hot/ sitting in traffic for ages
it also gets quite hot when i turn the A/C on whilst driving.... the electric fan is spinning the right way and all, it can get to 3/4 even higher on the gauge

any suggestions will be considered thanks for looking!

[edals]

Im Suspecting 02 Sensors mate, general cause for such a huge amount of fuel usage.
Since you have checked everything else and changed plugs leads etc, thats my next guess. Have you also changed the fuel filter ?

[mwemy]

yes fuel filter was changed when plugs etc were done, does anyone have the spec on howmuch OHM's im suppose to be getting from the o2 sensor? or are they that cheap its just worth changing ? also wouldnt the o2 sensor show up as a code??

[Z2TT]

Hi,

List of things that can affect fuel economy.

- Dragging brakes
- O2 Sensors
- Clogged fuel injectors
- Dirty Air Filter
- Fuel filter
- Airflow sensor
- Water temp sender bad, not sure if VR's have a separate one for the ECU, if yes this should be checked and replaced.

I'm pretty sure the ECU should put out an error code if the Oxygen sensors are not functioning correctly.
But the oxygen sensors should give a voltage from 0.1-0.9 volts, fluctuating up and down. Be sure to know
which wire to test on them, there may be an easier way to check the voltage through some check connector too,
or auto electricians can plug a diagnostic tool to the car to test.

[mwemy]

im gonna unplug the o2 sensor and see if it even makes a difference or wether i get a code or not and go from there, if nothing then new sensor it is!

[wortus]

Have you checked it for codes already? When the O2 sensor in my VN was on it's way out the engine light would come on every now and then but not all the time. As above I'd be jacking it up and checking for dragging brakes by spinning the wheel or looking for uneven pad wear.
I'd also be replacing the air cleaner element. I wouldn't be driving with the )2 sensor disconnected just check the brakes and get a new air cleaner and if the milage is still as bad go and get a new O2 sensor. Shop around for a genuine one as I found prices varied from $50 to $100 for the same AC delco part depending on which Holden dealer I rang. Also when you put the new sensor in don't use any anti seize other than what is already on it as some compinds contaminate and ruin the O2 sensor.

[PanthaVS]

from memory... if your o2 sensors fail... doesn't the computer go into a closed loop setup, where it will run really rich to protect itself?

this would result a lot like somewhere in the vacinity of 22ltr/100km ... wouldn't it?

[The1]

from memory... if your o2 sensors fail... doesn't the computer go into a closed loop setup, where it will run really rich to protect itself?

this would result a lot like somewhere in the vacinity of 22ltr/100km ... wouldn't it?

You mean limp home mode? Closed Loop is everyday operation. The only real way to know if you o2's are working correctly is with a scantool or laptop hooked up to watch for crosscounts, o2's get lazy and the computer wont set a fault for that as there still working.

[Z2TT]

Also see how they respond when you create rich and lean conditions, what does the VR Senator normally use, 17/100 ? it's a V8 or V6?

Could also be defective ECU, bad capacitors inside.

[PanthaVS]

You mean limp home mode? Closed Loop is everyday operation. The only real way to know if you o2's are working correctly is with a scantool or laptop hooked up to watch for crosscounts, o2's get lazy and the computer wont set a fault for that as there still working.

Yes... sorry... thats the one...

[mwemy]

well, ive changed the o2 sensor and nothing has changed, do i have to reset the ecu somehow? i wouldnt of thought so since its only a sensor.

also i felt my fuel regulator and it seems to be pulsing / knocking quite hard and the injectors are quite noisy, but i didnt think that would change the fuel consumption

brakes are not dragging either, they are free as a bird, the car also hunts at low speeds, but i duno wether thats cause of the higher stall or something is wrong wich in turn causes this fuel consumption

[The1]

You need to reset your ecu your fuel trims will be way out of whack if the sensor was stuffed the new one will adjust it back but not instantly it will take a tank of fuel

[mwemy]

this may be a stupid question but how do i reset my ecu ? i found something about battery off for 10 mins then revs at 3000rpm for 30 seconds, but that sounds pretty wierd to me....

how do u reset a VR ecu?

[The1]

pull engine fuse for 30mins or disconnect battery

[mwemy]

mate just told me to pull out the ecu lol, so i did that, spose it should have the same effect...

[pjdm1980]

Maybe a block catalytic converter.

[mwemy]

converters are high flow stainless steel bastards that u can basicly see straight thru them lol and the rest is brand spankin new,

i just hooked the ECU back up and started her up, the car seems to be ALOT quite'r now and the idle is higher ~850rpm instead of ~650 as usual, the car doesnt idle up when i put the A/C on tho, im thinking my IAC is still buggered?
seems its running a bit leaner but only time will tell what ill get out of it, i rang coventries today for a IAC valve but they dont seem to know what im talking about and want a part number..... do they just get stuck and need the carbon cleaned out or something ?

OH and another thing, my fuel gauge and temp gauge dont normally work until i give the top of the dash a little tap, but they worked straight away after the ECU was reset lol.... related??

[mwemy]

Im thinking I got a bad earth, my lights on the dash dim bad when I use my windows or indicators lol

[WogBoyz]

Hi,

List of things that can affect fuel economy.

- Dragging brakes
- O2 Sensors
- Clogged fuel injectors
- Dirty Air Filter
- Fuel filter
- Airflow sensor
- Water temp sender bad, not sure if VR's have a separate one for the ECU, if yes this should be checked and replaced.

I'm pretty sure the ECU should put out an error code if the Oxygen sensors are not functioning correctly.
But the oxygen sensors should give a voltage from 0.1-0.9 volts, fluctuating up and down. Be sure to know
which wire to test on them, there may be an easier way to check the voltage through some check connector too,
or auto electricians can plug a diagnostic tool to the car to test.

Just to add to that, not pumped up tyres will give u bad economy too

[mwemy]

Lol I hope ur serious, tyres?!? Not 22l/100 dude, I checked my injectors today and the flow rate was way off on 2 injectors, sonic cleaned them and also cleaned my iac but to no avail..... I'm kinda stuck now... Any suggestions??

[The1]

lead foot? lol

Coolant Temperature sensor?

[T-rex]

Lol I hope ur serious, tyres?!?

If they have more air in them they have less rolling resistance, within reason that is because you can only put so much air in.

[mwemy]

Nah I don't have a lead foot at all, is the coolant temp sensor the one at the front of the block? Wich one feeds the ecu? Wich one feeds the dash?

[dirt drifter]

yep it is, prick of a thing to get at too. the guage sender is just 1 wire the ecu sensor is the 2 wire plug

[mwemy]

mmm, should probably buy a gregories manual or something lol...