Thread: '98 P38 Overfuelling

With those figures it would be well worth fixing. I would change the oxygen sensors, cheap 4 wire generic Bosch types, easily fitted just need to fit your old ones plugs. Get a new Maf from the UK, again very affordable. As the plugs are newish remove and clean. New air filter if the other one is past it and see how she goes

I assume the '98 has a fuel pressure regulator on the fuel rail on the engine. Check that the vacuum hose from the regulator to the manifold is connected and not showing signs of fuel leaking from the regulator into the manifold.

Thanks wayneg! That sounds good. The air filter is new. A new MAF from UK is a little hard, as I am doing a 4 month trip around AUS with the Rangie right now. -> Can't really wait around for parts.

I did just clean it though, so I'd rather just try my luck on other options first.



I will get the fault codes read before I do any more work on the car.

Could a stored fault cause this over fuelling issue? (bypassing o2 sensor)



Ultimately new o2 sensors seems like the way to go. Does anyone have experience fitting the generic sensors to the 98 model? I read there are differences in the voltages between the years. Is there a parts finder somewhere I can use?

I just fitted some new O2 sensors to my 98 year build. I'll dig out what I bought and PM you the details.

Very early cars had 2 wire sensors the rest 4 wire. You can pick up universal Bosch type 4 wire lambda sensors real cheap I got 2 for A$36 the pair shipped on special. You can even get Genuine universal Bosch if you want branded. The difference is the Plug, If you are happy to cut the plug off the old and fit to the new with the supplied crimps you can save a bundle. Go with ones suggested for European rather than Jap cars and you should be fine. E-bay and aliexpress are your friends here.

there are 1, 2 , 3 and 4 wire sensors so beware, you want 4 wire with 2 whites, grey and black, These are type colour schemes so get the right colours and you should get the right sensor
here is an example.....Universal Lambda Sensor Oxygen Sensor 4 Wire High Quality | eBay

Sounds like it may be running in "open loop" configuration which provides a richer fuelling map. There may be several reasons for this including a dud MAF, cleaning may not be enough. Have you checked the oil separator in the top of the rocker covers are not clogged?

IF you have an Android phone or better still an android tablet with GPS , get yourself a Bluetooth dongle with an OBDII plug on it ($25) and download Torque (pro) ($5). You can then plug the dongle into the connector under the glove box near the transmission tunnel and detect all sorts of parameters including O2 sensors, fuel trim values, and generic trouble codes...

EDIT: how much stuff do you have on the roof rack? Once you get past 80kmh the aerodynamic drag becomes significant. For example, there is a 50% increase in drag when the speed increases from 80km/hr to 100km/hr...

Thanks for the info on the o2 sensor. Will shop around for a generic one then



I don't have an Android phone to use as obd scanner though. I am still looking for a shop that will sell me a simple scanner that can read and reset codes for under 120aud. (and have it in stock)

So far no luck. I am in Adelaide now so if anyone has a tip, much appreciated.



Hoges: I have a lot of stuff on the roof. It is the rhino rack XL mesh basket which spans the whole roof. Its loaded roughly 50cm high with a weight of about 50-60kg.

I am not expecting any fantastic fuel figures, just don't really want to hit the servo every 450km

I really keep the speed to about 90kph on cruise control for longer highway trips. (engine running at about 2k rpm)

Originally Posted by Hoges

Have you checked the oil separator in the top of the rocker covers are not clogged?

I have not checked this. Is the separator easy to remove or do I have to look out for anything? This would be a part to get from the dealer I assume?



I just read about this a little and it could well be clogged. My rocker gaskets have been known to leak a little every now and then (read: constantly). I just tightened the bolts down and called it a day, but this may explain it...



Sorry for the double post, can't edit on my phone.