Vct And O2 ... Help!

[nickalls]

Hi There,

I've just brought a 1995 GTS-T (S1 RE25DET), it's my 1^st skyline and I’m loving it however I’m not loving the quirks it’s got. Currently it’s doing 250-300km per 60L tank!! L I’ve spent hours and hours poring over forums to try and get an understanding of how this could be happening but its only lead to more questions… So far I’ve checked the following things and have picked up two potential problems

Purchased Consult cable – all sensors bar the o2 one seem to be ok?

Coil packs running ok

AAC valve taken off, cleaned, tested, re-fitted

Idle adjusted

Injector cleaner run through system

new fuel filter

O2 SENSOR FAULTY?

I noticed the o2 sensor has some strange readouts when the engines going (driving)? I assumed the voltage would creep up the hotter it got but it flicks back and forth between 0.2-3 and 0.8v is that normal?

VCT/VTC PROBLEM?

The second thing I noticed it that it has a funny idle. It only seems to happen when it’s at operating temperature and the only way to describe it, is, it’s a bit ‘lumpy’. When looking at the live readout using the consult cable, the timing is all over the place 0deg-15deg. I’ve checked forums and from what I can gather it seems to be the VTC solenoid is stuck open? So I took it off today and yes its stuck open but here’s where it gets tricky… I tested the solenoid and when I apply 12v to the terminals the valve closes??? Interesting! I then put the solenoid back and started the engine, instantly lumpy, I applied 12v to the solenoid, valve closed and idle returned to normal, timing at a steady 15 deg, smooth as! WTF?

Now, on all the forums I have read people believe that the valve is closed then is opened by the ECU at 1050 until 4500 rpm for a midrange power increase. So why is my solenoid/valve doing the opposite? Is the ecu meant to supply power to it during idle to keep it closed? Then power off at 1050-4500rpm to allow the spring to open the valve?

I’m so confused!! any ideas about these two issues guys?

Thanks,

Nick

[blind_elk]

Can't answer about the VCT solenoid.

Injector cleaner is basically a maintenance additive.You really need to get the injectors sonic cleaned (which entails removing them from the rail) if you hope to remove any contaminants. Then use cleaner to maintain the cleanliness.

The O2 sensor has a built-in heater so that it can sit further down the exhaust system. It relies on the heater and the exhaust gases to maintain the correct operating temperature. The sensor is doing exactly what it should, assuming the engine is under constant load / revs. Any other condition, particularly acceleration, and you (and the ECU) can ignore anything the O2 sensor says or does (it will generally show close to 1V under acceleration).

[W0rp3D]

There is one important part you have not checked out, your right foot, if you keep bringing the car onto boost and giving it stick then that fuel consumption is not unusual.

[nickalls]

There is one important part you have not checked out, your right foot, if you keep bringing the car onto boost and giving it stick then that fuel consumption is not unusual.

I had concidered that but I doubt it. Have you ever heard of a car coming off the production line that does that mileage? - if you google r33 bad fuel consumption, alot of our R33s are having similar issues? I really believe that there is something wrong with the VCT/VTC. Either the ECU is not giving it the correct signals or the soleniod valve is not operating correctly. Is anyone keen to run some checks on their r33s for me?

Is the valve open or closed with no voltage going to it?

Is there power going to the solenoid with the ignition off? - ignition on? - engine started? - engine over 1050 RPM? - engine over 4500 RPM?

I can't seem to find anything in the service manual about the operation of this system? Any help would be really, really appreciated!

[W0rp3D]

lol, your car has not just rolled off the assembly line, its now 14 yrs old, how many cars do you know of that get the same mileage 14 yrs after it rolled off the assembly line?

My car was getting the same mileage as yours, if i drove it normally and didnt bring it onto boost the economy was much better, i then had it tuned with a pfc and the economy was much better whilst bringing onto boost.

Also how much boost are you running, the standard ecu has a habbit to be really rich when you increase the boost.

[4NTM4N]

i got same model an mine is like that aswell, i could prob push 350km out of a tank if i drove like a nanna but who does that?...

my guess for mine is that its running rich, needs a tune or something, my exhaust also pops alot when i am drivin around

[nickalls]

i got same model an mine is like that aswell, i could prob push 350km out of a tank if i drove like a nanna but who does that?...

my guess for mine is that its running rich, needs a tune or something, my exhaust also pops alot when i am drivin around

I agree it's getting old but I know there's a problem somewhere. As soon as it starts idling rough (the VCT thing) i swear i could stand at the back of the car, light a match and i would be history :-( it's running that rich. When i pull up at the lights, i sometimes wind up the window to aviod the unburnt vaporised gas smell ... it's bad.

I have the consult cable but can't afford to fork out $100 euros or what ever it is for nissan data scan v1.52 to run the VCT scan... thought i'd be able to find an open source one but only found ECUtalk whick doesn't do scans, just readouts. I just don't get whats going on with the solenoid?

[paulr33]

it wont be the VCT - so dont even worry about that

in order to get good economy

1) pump up tyres - 40 psi is good

2) replace 02 sensor - they die after around 50,000kms, $120 part

3) reset the stock ecu

4) dont vary the throttle constantly, ie changing speed/gears, a steady throttle allows the ECU to run in closed loop mode

when the load is constant (not changing) the ECU will monitor the 02 sensor readigns and trim fuel

it does this purely for the sake of fuel economy and nothing else, ie; its not boost related etc

as soon as you vary the throttle, ramp the engine on load, bring on boost etc, it drops out of closed loop mode

and if all that fails

give the car with a full tank to your girlfriend or mother and let them drive it for a week

i bet they get good economy of out it - ie they dont load the engine up constantly and rape it flat out

[nickalls]

it wont be the VCT - so dont even worry about that

in order to get good economy

1) pump up tyres - 40 psi is good

2) replace 02 sensor - they die after around 50,000kms, $120 part

3) reset the stock ecu

4) dont vary the throttle constantly, ie changing speed/gears, a steady throttle allows the ECU to run in closed loop mode

when the load is constant (not changing) the ECU will monitor the 02 sensor readigns and trim fuel

it does this purely for the sake of fuel economy and nothing else, ie; its not boost related etc

as soon as you vary the throttle, ramp the engine on load, bring on boost etc, it drops out of closed loop mode

and if all that fails

give the car with a full tank to your girlfriend or mother and let them drive it for a week

i bet they get good economy of out it - ie they dont load the engine up constantly and rape it flat out

You make some good points and I'm going to take up your advice on the o2 sensor but I'm not wrong with this VCT thing. If I apply 12v to the VCT solenoid when the engine is at idle and up to temp (when its doing its rough idle thing), the valve closes and timing returns to normal - 15 deg instead of all over the place - no unburnt fuel smell either. I just need a kind volunteer to help us out with some readings :-D Anyone game to set some records straight about VCT????

Is the valve open or closed with no voltage going to it?

Is there power going to the solenoid with the ignition off? - ignition on? - engine started? - engine over 1050 RPM? - engine over 4500 RPM?

[mosquitocoils]

Hey Nicholas, I've got the exact same thing going on with my car. Lumpy idle (not missing or anything like that, just makes a 'breathing' noise maybe once every 1-2 seconds consistantly).

Thought it might be my timing, so I bought and hooked up ECUtalk, and my timing reading is all over the place between 0 - 15 deg as well... I can't figure out why!

Next thing I'm going to try is check/adjust the timing at the CAS, just so I know what it's set to, and just to rule it out for further problems.

I'll keep you posted.

[mad082]

the timing that the ecu is showing isn't the same as the timing you would read if using a timing light. the ecu can alter the timing. it is normal for the timing to fluctuate like it is. if the timing stayed the same throughout the rev range then you could find the car rather different to drive as in certain parts of the rev range it would be well down on power. this is one of the reasons why modern cars make more power than the old carby cars. the ecu can alter both fuel and ignition.

[frozenwaffles]

the timing that the ecu is showing isn't the same as the timing you would read if using a timing light. the ecu can alter the timing. it is normal for the timing to fluctuate like it is. if the timing stayed the same throughout the rev range then you could find the car rather different to drive as in certain parts of the rev range it would be well down on power. this is one of the reasons why modern cars make more power than the old carby cars. the ecu can alter both fuel and ignition.

actually if the cas is set correctly then the timing would display exactly what the ecu is commanding.

Dude fix you vct, very simple. It's a good chance why your consumption is bad.

0-1050rpm it's off

1050-4500rpm it's on

4500-6900rpm it's off

[mosquitocoils]

How hard is it to find/get to/replace the VCT solenoid? I have no idea where it is

[MrStabby]

O2 SENSOR FAULTY?

I noticed the o2 sensor has some strange readouts when the engines going (driving)? I assumed the voltage would creep up the hotter it got but it flicks back and forth between 0.2-3 and 0.8v is that normal?

The o2 sensor should flick back and forth when its up to temp - that indicates it working (assuming the voltages are right, cant remember what they're supposed to be). Its the ECU is hunting for stochiometric mixture (which the factory narrowband o2 sensors cant read).

[NewKleer]

thought i'd be able to find an open source one but only found ECUtalk whick doesn't do scans, just readouts. I just don't get whats going on with the solenoid?

you must have missed the fault codes tab if thats what you mean by 'scans'. look up the top or bottom of program window, you'll set the setup, fault codes, options, etc.

[Fido_]

try search in forum : AFM CLEANING

i used to have fuel consumption problem until i clean it with alot of wd40 or something like that.. all the carbon is clotting up in the pipe after that clean... you'll probably get 400-450ks per tank.. roughly..