'98 P38 Overfuelling

[RangerFelix]

Hey Everyone,



I've just registered and this is my first post. I've been using this forum to help me along fixing the (many) various issues that have come up on my (beloved) 1998 4.6 HSE Range Rover. So first off: thank you all for your valuable contributions :)



I have an issue where I am not sure if it is worth fixing: The engine seems to be running too rich. It has no issues running and always starts up nicely.



The main problem is the fuel consumption: 17l/100km on pure flat highway cruise control at 90km/h. (Fully loaded with a roof rack) In the city it gets around 23-24 liters.

That seems a little high to me, or am I crazy?



The other issues I have discovered are fouled spark plugs (all of them, 1500km after changing them, dry black carbon) and a smell of fuel when opening the oil filler cap.



I have recently changed out all spark plugs, the air filter and cleaned the MAF (with CRC cleaner).

Fuel pressure tested at the rail: seems stable and holding at correct pressure when idling.

O2 sensor and others were (supposedly) checked by a mechanic in Melbourne (fixing the EAS). He told me all sensors seem to be reading out just fine.



So my question is: what could be the cause? And is it worth chasing down? (should I be expecting drastically better economy?)





Thanks in advance,

Felix

[wayneg]

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

[bee utey]

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.

[RangerFelix]

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?

[davidsonsm]

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

[wayneg]

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 (http://www.ebay.com/itm/UNIVERSAL-LAMBDA-SENSOR-OXYGEN-SENSOR-4-WIRE-HIGH-QUALITY-/250984739999)

[Hoges]

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...

[RangerFelix]

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)

[RangerFelix]

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. :(

[TheTree]

Hi

I am still having fun finding why I get a misfire on LPG and heavy fuel consumption.

I concur with the other things said here, I have replaced my MAF, O2 sensors and fuel pump, all needed replacing

Vacuum leaks could be an issue.

I am now checking for vacuum leaks, and have purchased an inexpensive vacuum tester to check it.

If you can afford it get a nanocom or hawkeye rather than a generic diagnostic tool, you get a huge amount more information. Although the generic ones are better than naught!

I am now getting a fault on one bank only, so am about to swap the o2 sensors and see if the fault changes sides :angry:

Steve

[RangerFelix]

Just a quick update: got a code reader - no fault codes.



Bee utey: checked the fuel pressure regulator. No signs of a fuel leak. But I could not find a vacuum hose. I will check RAVE and take a look maybe I'm just looking I the wrong place...

[RangerFelix]

Just found the vacuum hose for the fuel pressure regulator. It is in pretty bad shape. Has a crack in it. No signs of major fuel leaks, but I'll be replacing that asap. Could that be the cause of over fuelling?

[bee utey]

Just found the vacuum hose for the fuel pressure regulator. It is in pretty bad shape. Has a crack in it. No signs of major fuel leaks, but I'll be replacing that asap. Could that be the cause of over fuelling?
Absolutely. a leaking vac hose at the reg means higher fuel pressure at light load which means extra rich as the fuel map can't cope. I see this all the time.

[RangerFelix]

Okay. I've replaced the hose. Had a little drive. No noticeable improvement. The old one seems to still be able to hold a vacuum. Still taking too much petrol. (18l/100km empty & nothing on the roof rack on a country road at 50-60 - according to trip computer)



Just checked the fuel pressure at the rail again. 29psi while idling and 20psi with the engine off and ignition on. I checked it with a tyre air pressure gauge. That's too low right?

Also just cleaned the oil separator. That was a bit messy. Likely the engine had a hard time breathing through that. Will see how that affects the engine running tomorrow.

[bee utey]

Okay. I've replaced the hose. Had a little drive. No noticeable improvement. The old one seems to still be able to hold a vacuum. Still taking too much petrol. (18l/100km empty & nothing on the roof rack on a country road at 50-60 - according to trip computer)



Just checked the fuel pressure at the rail again. 29psi while idling and 20psi with the engine off and ignition on. I checked it with a tyre air pressure gauge. That's too low right?


The pump pressure should climb by about 10psi when it is at full load as the injector pressure is supposed to be held at a constant level above manifold vacuum. You can mimic full load by temporarily undoing the vacuum hose. Unfortunately it sounds like your system is working normally and your problem is elsewhere.

BTW I wouldn't trust a dash readout of l/100km all that much. You should calibrate your settings by driving fill-to-fill and checking the odo against a GPS or road markers on a highway. You could easily be 20% out overall.

[Keithy P38]

Out of curiosity RangerFelix, what size are your tyres?

[RangerFelix]

Out of curiosity RangerFelix, what size are your tyres?



265/70 R16 BFGoodrich All-Terrain T/A



Running them at 34psi all round.



They are Muddies that the previous owner put on there. Really annoying, because they are too big so when the EAS is in access mode the tyres hit the wheel arch when turning.



These no doubt contribute to the bad fuel economy. I will change them, but only after this trip, so in about 3 months.

[TheTree]

Okay. I've replaced the hose. Had a little drive. No noticeable improvement. The old one seems to still be able to hold a vacuum. Still taking too much petrol. (18l/100km empty & nothing on the roof rack on a country road at 50-60 - according to trip computer)


Hi

I would not place a lot of credence on the trip computer consumption figures, it is an average based on how much fuel the injectors are getting so it may take a while to see nay change there.

Much better to fill the tank and do it the old fashioned way

Steve

[RangerFelix]

I'm not placing much trust into the trip computer figures. The figures from the initial post are calculated from the tank fill and km. I was just looking for some ballpark figures. The last couple of fills were very accurate on the trip computer for me.

Will be doing a bigger trip today, so I'll know of there's any change. Likely I'll still fit a new MAF and o2 sensors.



A blockage in the crankshaft breather (oil separator) wouldn't cause excessive fuel consumption, right?

[wayneg]

265/70 R16 BFGoodrich All-Terrain T/A



Running them at 34psi all round.



They are Muddies that the previous owner put on there. Really annoying, because they are too big so when the EAS is in access mode the tyres hit the wheel arch when turning.

These no doubt contribute to the bad fuel economy. I will change them, but only after this trip, so in about 3 months.

With those tyres you are at least 10% on your fuel KPL and speed readings so right away your 18l per 100k is 16ish. As previous poster, Get a gps logging distance, fill to brim then work it out exactly at next fill up

[TheTree]

A blockage in the crankshaft breather (oil separator) wouldn't cause excessive fuel consumption, right?

Hi

It may if it is causing a vacuum leak

There are some threads on here about how to get the buggers out on the Thor engine :twisted:

Steve

[RangerFelix]

Hi

It may if it is causing a vacuum leak

There are some threads on here about how to get the buggers out on the Thor engine :twisted:

Steve




Thanks Steve. I've cleaned the breather. Not too bad to get out just need to take some time, but I managed to pull the whole thing out without anything breaking. Gave it a good clean and popped it back in.



Drove around today, but not enough to make any assumption on changed fueling.



Got a new (used) MAF from Triumph Rover Spares in Adelaide. (Along with some other small bits). Popped that in. Doesn't feel any different to using the original (cleaned) one.



Concerning the tyres and trip computer: its been pretty much spot on for me. Comparing GPS kilometers and tank fills for the last 3 tanks the trip computer has been within 0.2 l every time. I was pretty impressed. Speed seems perfectly accurate too. Maybe the tyres are balancing the inaccuracies of the trip comp :)



Like I said it doesn't feel any different. Was running nice before I did anything though, so that's not much to go on. The only thing I seem to notice is that on a kick down, the power doesn't seem to be quite there. I can fully press the accelerator and the engine won't rev over 3k rpm. Is that normal?

[mtb_gary]

RangerFelix, I've got a 1996 HSE (4.6 GEMS) running 91 octane petrol only. Put the foot down and revving to redline without a problem. As for fuel consumption, that comes back to how I am driving. If I drive sedately and dont get over 90 kph on a country road aside from annoying every driver in a vehicle behind me I can comfortably acheve around 13l/100K. Lift the speed to 110+ and a bit more aggressive with the right foot and the fuel consumption will move up to around 17l/100K. Those figures are whilst running with "standard" size tyres 255/55/18 highway tread. If I switch to the 265/75/16 Maxxis Big Horn muddies, firstly the speedo and subsequently the calculator is out by around 10% but using GPS and actual fuel being put into the tank I am getting around 18l/100K with highway speeds of 110+ kph.

On a trip that I did back in 2012 I had a fully loaded car plus roof rack also heavily loaded. 5629.7 K's and averaged 17.22 L/100k. That included driving around 1200 K's of gravel roads and around 250 k's of sand driving, I was then on Cooper ST's 225/75/16.

Gary

[davidsonsm]

Gary. That sounds about spot on with what I get. Nice to see some repeatability.

[RangerFelix]

Those figures you're reporting are what I'm expecting from this car. Sadly its not what I'm getting.



I've today just done about 30km on the highway and decided to see how the car is responding to the recent adjustment.

Result: I've discovered a complete lack of power. I may have just not noticed this previously, because I was driving the thing like a grandma to save fuel. So this may be a new issue or an existing one.

Basically what happens is it will go fine to about 100kph, albeit very very slowly. (like 30-40 seconds, bot like a 4.6 V8 should) This is with the gas pedal to the floor. The rpm maxes out at 3000. It feels like it is struggling hard to get to that speed.



I've just ordered new HT leads which I will hopefully be able to fit this afternoon.

Also just checked the transmission fluid: was low so I've just topped that up.



Any ideas? I love that range rover, but it really is a bit of a money sink :D

[bee utey]

It's not unknown for catalytic converters to block up, especially if they've spent a number of years running rich, from short trips etc. If your engine is running at full throttle it runs open loop and rich so it only compounds the problem. You can either smash out their guts with a rod (illegal but invisible from outside), cut them out and fit plain pipes (more illegal and visible) or replace them with aftermarket hi flow cats. You could have a collapsed muffler baffle too.

[glenhendry]

What does exhaust smell like? What are your long term fuel trims? You really need to watch ODBII values for a while and Id suggest for a while to stop throwing parts at it. If it starts and runs well, it must be something small. Small vacuum or exhaust leak?

ODB LTFT will tell you if its both banks or just one. The bluetooth adaptors are cheap and can connect to Apple or Android or laptops. Itll be useful for other stuff too. The Kiwi one is excellent, flawless.

I have been chasing rich problems on both banks for months. I cant find it. My LTFTs are ~23%. And it smells rich, you can tell in the garage after only a few seconds. I have tried O2s, MAF and new inlet ducting. My last suspicion is inlet manifold.
http://www.aulro.com/afvb/p38a-range-rover/172248-high-long-term-fuel-trims-why.html

Good luck!

[glenhendry]

If it doesnt smell rich, and you havent got any faults, then it is probably not too rich?! Maybe dragging brakes, dud bearings, handbrake?

BTW: mine eventually throws fault codes on both banks, but does NOT fail into open loop mode. It stays in closed loop operation. And I have one knock sensor short to ground that I suspect is unrelated.

[mtb_gary]

Right back on your first post you mentioned that the plugs foul up after 1500k's. Not normal. Are the gaps set correct and are they the correct plugs? If the car is stationary and in neutral will the engine rev over 3000 rpm or is it only when under load?

Gary

[RangerFelix]

Right back on your first post you mentioned that the plugs foul up after 1500k's. Not normal. Are the gaps set correct and are they the correct plugs? If the car is stationary and in neutral will the engine rev over 3000 rpm or is it only when under load?

Gary




Yep plugs are fouling after a short amount of time. Correct plugs (ngk brp6es), previously used ones (from previous owner) were not correct plugs.




Tried some more stuff today. The car will rev fine in park or neutral. Also when using the "manual" gears it will rev higher. In sport it will go to 3500rpm roughly, then it will change.



Just installed new HT Leads. Haven't given those a try yet.



The catalytic converter sounds interesting. If I poke in the exhaust I can feel something loose and rusty in the end. That would be my muffler though I assume? Cats sit further in don't they?

[Keithy P38]

Yes, the cats are under the two front seats.

[mtb_gary]

RangerFelix, I should stress I am not a mechanic, so I may be on a wrong tangent with the diagnosis. The good news (well sort of good news) is that you have traced the problem back to the motor and eliminated transmission, brakes bearings etc...The fact that all the plugs carbon up after 1500k, to me, indicates that the problem is global to all cylinders and is not unique to one bank of the motor. There are 2 Cat converters one for each exhaust manifold, so I'm inclined to think it improbable (not impossible) for both cat converters to collapse at the same time.
Maybe start with a few less invasive tests first? I was thinking firstly checking the air intake of the air filter box. Also check that the throttle physically opens when the accelerator is pressed. Are there any modifications to the intake system that have been carried out by a previous owner?
Failing finding any blockages or restrictions I would be looking to get the car hooked up to a Nanocom or similar to see what fault codes come up.

Good luck

Gary

[TheTree]

I have tried O2s, MAF and new inlet ducting. My last suspicion is inlet manifold.
http://www.aulro.com/afvb/p38a-range-rover/172248-high-long-term-fuel-trims-why.html

Good luck!

Glen

I picked up a vacuum gauge for 26 bucks from ebay and am going to use it to check the inlet system for leaks, they can also tell you about other engine issues, worth the investment

Steve

[TheTree]

HI

As others have said, reading fault codes is the way to go, cheapest is a wifi elm327 adaptor and an app which will tell you a lot about your ECU.

Much better is a nanocom, faultmate or hawkeye but they are not a necessity.

Steve

[RangerFelix]

I feel kinda dumb now. The lack of power was due to a (very) maladjusted throttle. Readjusted that and voila...power is back.

Car is still over fuelling. I will try new o2 sensors next.

There are no stored faults in the ECU.

[mtb_gary]

Don't you just love finding out that it was cheap and easy fix? Amazing how we fear the worst though on a p38 :angel:

Gary

[Keithy P38]

The ECU might re-learn the fueling settings now you've fixed the problem!

[davidsonsm]

You should have a fault code via the OBDII connector if the O2 sensors are causing the engine ECU to default to runnung rich. Worth checking before you buy new Lambda's.

[RangerFelix]

You should have a fault code via the OBDII connector if the O2 sensors are causing the engine ECU to default to runnung rich. Worth checking before you buy new Lambda's.





I read the fault codes. There were none.



Just a little status update: drove 1000k's since I adjusted the throttle. Now power is back. Fuel consumption is still not good.



19.4l/100km on dirt at 80-90kph cruise control (Parachilna to Coober Pedy).



Do faulty lambdas always throw a fault code?



Just to sum up here is what I've done:

New air filter

New MAF

New spark plugs

New ht leads

Read fault codes - none found



When I start the car I can smell that it is over fuelling. Exhaust is coming out of the pipe - not black though. So it doesn't seem like the cats or muffler are blocked.



Thanks for any help :)

[TheTree]

Hi

One other thing which can cause rich running is a tired fuel pump providing low fuel pressure.

Or possibly a vacuum leak on the air intake system or plenum

Steve

Steve

[glenhendry]

How did you go here RangerFelix?