4litre poor fuel economy

[jamienshelly]

Hi all. Trying to get on top of my new purchase and i have found a few things wrong, like the vac advance not working and maybee a dodgey ecu temp sensor have got new to fit but i am using vast quantities of fuel. strong smell of petrol at exhausts so must be running very rich. Would the the vac advance and possibly ecu temp sensor cause this much usage or is it more than likely to be the afm aswell. will be changing thermostat and guage sensor also as it takes a while to warm up, but even at warm it is costing about a £1 a mile (unable to get accurate mileage as is digital odometer and i assume battery is flat). Any suggestions would be grately received.
Many thanks
Jamie

[carsy]

The vac advance not working wont have this much effect. many dont run with it anyway. Could well be the ecu temp sender but more likely the afm.

[ChimpofDarkness]

First off do the Range Rover temp sender mod, although this wont solve the overfilling as such, at least for the first time you can see what the true coolant temp is.

NEXT:

• Replace the ECU temp sensor (it's different to the one above)

• Replace the thermostat, someone may have fitted a lower temp one in the past, you want a decent 82 degree German stat

• Replace the fuel temp sensor in the fuel rail

• Spray some carb cleaner down the air flow meter

• Disconnect the ECU & reconnect it to clear the fault codes

• Test

These cars have a weak spark as it it is, anything marginal on the ignition side can cause the car to overfuel as the fuel just doest get burnt properly especially when cold starting & at low RPMs.

Every element on the ignition side needs to be in tip top condition, plugs, coil, HT leads, ignition amp ect.

If the problem persists after the above bullet points have been addressed and you have given it a full ignition service, you may want to invest in a ECU Mate.

Faulty lambda sensors can cause overfueling but they are expensive you don't want to go replacing without testing them.

The ECU Mate will give you the fault codes you need to replace the right component first time, you may feel it makes more sense to invest in one in the first place.

Otherwise you are just replacing components that MAY or MAY NOT be at fault, in the hope the problem will go away.

Good luck with it.

[jamienshelly]

Thanks for your prompt replies, I have tested the ecu temp sensor and doesn't seem right according to the bible, but i feel that you are right and i will have to invest in an ecumate as fault finding by bit changing could/would cost more than the fuel that i am using. Also have checked timing and found to be spot on and tested spark and good strong spark present. did not think of fuel temp sensor so will test/ replace aswell.
Many thanks again
Jamie

[edo]

Ours was chomping through petrol hideously. New MAF fixed ours.

[jamienshelly]

Thanks again for all of your input. Is the 4.0 afm the same as 5.0 and are they interchangable as one for sale on an auction site. will try to test and clean first. even though its juicy the smiles per gallon are worth it, its just not very practical.
Jamie

[Hoofa]

Whats is the temp sender mod ??

[ChimpofDarkness]

Hoofa said:

Whats is the temp sender mod ??

Google is your friend

http://lmgtfy.com/?q=+site%3Apistonheads.com+range...

[blitzracing]

You can do a really simple test on the temp sender- just measure the water temp sender resistance, and the fuel rail temp sender on a cold engine- they should read the same as the devices are the same value- just different fittings at the screw end. If the exhaust stinks that badly, the ECU is likely to be in fall back mode, and ECUmate or RoverGauge will tell you if thats the case. Double check the AFM connections, as no signal to the ECU from the AFM makes the car run on throttle pot and RPM readings only, or the other failing is the AFM voltage goes high so the car overfuels, but the ECU does not trip into a fault condition. A lack of vaccume on the dizzy will make the MPG worse as you dont get the correct ignition timing under light load, but not £1 per mile!

AFM testing here:

http://www.g33.co.uk/fuel_injection.htm

[penno]

AFM is a 5am lucas one found on a various jags, range rovers all the same dont pay over the odds they are quiet common. Yes a 500 is the same as a 400.

This site gives some info on testing and setup quiet simple

http://www.g33.co.uk/fuel_injection.htm

[blitzracing]

ChimpofDarkness said:

First off do the Range Rover temp sender mod, although this wont solve the overfilling as such, at least for the first time you can see what the true coolant temp is.

Good luck with it.

You have me on this one- Im not sure what the relevance is? If you add another "load" onto the lucas temp sender in the way of the TVR gauge, you will alter the temperature / resistance curve of the sensor in the first place, which is not a good thing as far as the ECU is concerned- it needs an acurate reading to get the fuelling correct. The TVR gauge may now be correct, but the ECU temp may not be...Im not sure what you mean by the Range Rover sensor? You have three sensors on the TVR, ECU water temp, Fuel rail temp, and Dash Temp gauge, and all three should really be kept separate. I can only see any advantage to messing around with the Lucas water temp sender with resistances to make the ECU think the engine was hotter than it was to reduce the cold start fuelling- as already discussed in previous posts on cold start fuelling.

[jamienshelly]

Thankyou all for your wisdom. Will check afm as in links and fit all bits as this cant hurt and will report back with good news hopefully. i know the vac assy would not help the issue due to the fact i know its using a lot of fuel so i am trying to be as gentle on the loud pedal which will only compound the fuel issue.
Thanks Carsy, Chimpofdarkness, Edo and Blitzracing
Will let you all know the outcome.
Jamie

[ChimpofDarkness]

blitzracing said:

ChimpofDarkness said:

First off do the Range Rover temp sender mod, although this wont solve the overfilling as such, at least for the first time you can see what the true coolant temp is.

Good luck with it.

You have me on this one- Im not sure what the relevance is? If you add another "load" onto the lucas temp sender in the way of the TVR gauge, you will alter the temperature / resistance curve of the sensor in the first place, which is not a good thing as far as the ECU is concerned- it needs an acurate reading to get the fuelling correct. The TVR gauge may now be correct, but the ECU temp may not be...Im not sure what you mean by the Range Rover sensor? You have three sensors on the TVR, ECU water temp, Fuel rail temp, and Dash Temp gauge, and all three should really be kept separate. I can only see any advantage to messing around with the Lucas water temp sender with resistances to make the ECU think the engine was hotter than it was to reduce the cold start fuelling- as already discussed in previous posts on cold start fuelling.

No one is suggesting changing the resistance values of the ECU temp sensor, that would be stupid!

You are wrong anyway, the TVR has four temp sensors/senders:

1) The TVR temp gauge sender they fitted in a blind spur thread adapter

2) The redundant (but still present) Range Rover temperature gauge sender

3) The 14CUX ECU temperature sensor

4) The fuel temperature sensor

See four, not three

I guess in your defence this is not overly obvious when you don't even own a TVR.

My suggestion refers to the temperature GAUGE sender.

As I clearly stated above:

"this wont solve the overfilling"

However, what's the point in having a temperature gauge if it doesn't tell you what the coolant temperature truly is?

TBH it's next to useless at the best of times, but when you have overfueling issues like the OP has, its downright misleading.

For example it's well documented the TVR gauge & sender combo reads ridiculously & incorrectly low on a run in cold weather, this might lead the OP (incorrectly) to think his car is never getting hot enough to come off cold start enrichment.

Many a thermostat have been replaced unnecessarily on these cars for just this reason.

Ginetta may not have the stupid blind spur thread adapter, but the OP's car is a TVR, & they do.

I was just suggesting before the OP starts trying to solve the overfueling problem he may benefit from a temperature gauge that actually tells him what the coolant temperature truly is?

It's not revolutionary and as I clearly stated "It wont solve the overfueling", but with a fault like this surely knowing truly how hot the coolant is makes for a good starting point?

It's a bit like trying to test resistance with a faulty test meter, worse than useless!

This forum works much better when contributors focus on helping people with issues not picking holes in other contributors attempts to help.

Especially when that sniping is flawed anyway.

Lets get back to helping the guy with overfueling issues shall we?

Edited by ChimpofDarkness on Monday 26th November 15:33

[blitzracing]

Not meant as a snipe- just a simple mis understanding that you wanted to use the old rangie unit- I did not realise they where still fitted. Ive not looked that closely on many of the TVR's I worked on.

[ChimpofDarkness]

blitzracing said:

Not meant as a snipe- just a simple mis understanding that you wanted to use the old rangie unit- I did not realise they where still fitted. Ive not looked that closely on many of the TVR's I worked on.

My humble apologies then Blitz, sorry.

Now back to the overfuelling issue.

In my experience they all overfuel a bit, especially on cold start.

You cant really alter that on the 14CUX, but you can attack it from the other end & improve the spark.

I wonder if the OP just has ignition trouble?

Could even be as simple as he needs a fresh set of HT leads & some new plugs?

If it needs plugs, I saw a big improvement by ditching the shrouded electrode NGK B7ECS and replacing them with a set of projected electrode NGK BPR6EIX iridium plugs.

What lets these cars down is the ancient distributor & coil, it's fine for what it is but things have moved on so far now you would be mad not to ditch it in favour of a better more modern ignition system.

It's all too easy to blame the poor old 14CUX when suffering overfuelling but I always found it a very reliable system when I had one, it's just a shame you cant map it.

The airflow meter is also an extremely sophisticated & reliable sensor and should not be underestimated.

Remember there are two sides to this, how much fuel is being chucked in, & how effectively it's being burnt.

The OP could well have the right amount of fuel, it just going to seem like too much because his ignition system may be letting him down.

Just another way of looking at it, clearly it's impossible to diagnose a fault like this on a forum.

However an old Sun Tuner machine, the ECU Mate, and a decent mechanic would have it all correctly diagnosed in half an hour.

Often it's cheaper spending some money on a professional with the right kit, than clutching at straws and just replacing components in the blind hope you'll stumble on the problem.

[V8Firm]

Jamie
I had a horrendous overfuelling issue with mine.....flooding, black smoke etc etc....tried changing temp sensor...no difference. AFM and ECU both swopped with another cars...still the same ...diagnostics showed no fault codes!!!!

Finally auto electrician called in and he traced fault to "cross talk" in the wiring loom...apparantly very rare fault... and really difficult to find having tried all usual suspects.

Both lambda sensors also had to be replaced ...as they were ruined with all the fuel going through.......

Hope this is not the case with yours....

[jamienshelly]

Thankyou to all who offered advice and it was well recieved. Just wanted to give an update on progress
Have changed sensors and thermostat, cleaned afm and definately not running as rich, but now the idle is suffering. It fluctuates when cold giving stepper motor fault so disconnect stepper and hunts and stalls even when warm. I pressume that it is now running lean and to much air, i have checked for air leaks and adjusted the air screw on the plenum as descibed in the bible ( 1.5 turns out) but no difference. will have to test lamda sensors as have read that if heater part is inop then the sensor will not operate correctly. Will let you all know how i get on.

[paulathome]

When you disconnected the stepper motor did you do it with the engine off or running?
If you turned off the ignition the stepper motor will have returned to it's park position so
the engine will always stall after that.
Might be better to reconnect the stepper motor then you wont have another fault to add to the mix.
If you want to run without the stepper motor messing things up then reconnect and warm the engine and while you have a nice idle unplug while the engine is still running. You may now find it wont idle at cold and you will need to give it a little throttle for the first few minutes.
Paul.

[carsy]

That base idle of 1.5 turns is only approx. Mine is at its best at about 2.5

[jamienshelly]

Hi paul, i unplugged the stepper motor when warm, and at idle after a short time really starts hunting and eventually stalls if left. i have just come back from giving it a run and i noticed that if i barely touch the throttle it will idle smoothly so it may be the plenum adjustment. Thanks again for your advice
Jamie