V8 3.9i problem ( Driving me mad!!)

[cookie55]

Hi, Got a probem with my V8 3.9i, It is a K plate Discovery left hand drive but is got no cats! And no signs of having any from new!!

When I first got the car it seemed fine but I never drove it as, it was damaged ( not hard) And been sat for a long time( few years) So I repaired it and started to make it my new off roader....... Got it all finished just about to take it for an mot and it would not start.. It would not even fire!! I tried a few things and found out it needed new plugs and fired up lovely.. Thought I had sorted it and took it out for a day and it seemed fine.. Parked it up and in a few days went to start it and the same happend again!! Everyone told me to put more new plugs in but I never did as I only just put new ones in!! I changed the dizzy/Air flow/ Cap/ Leads everything that I had spare, but nothing!! Chucked another new set of plugs in and it fired up!! Thinking I had a poo set of plugs and took it out for another day out!! Sure enough the next day it was running bad missing and choking up!! I tried to drive it to work and it died only a few yards up the road!! It seems to be over fueling loads... The plugs are jet black.. Even if I clean the plugs it doesn't work!! ( only new plugs will make it fire up) When its running it runs lovely!! So getting bored of buying new plugs ( tried ngk's and Denso Plugs) I got a mate that works in a toyota garage to get me some second hand plugs out of the service cars and chucked them in!! Fired up sweet.. I have had the timming all set up and changed the Fuel temperature switch! And found out it had no thermostat and put a new one in!! (thinking it was running to cold and telling the ecu lies) The car ran so much better and thinking I had sorted it I used the car for 3 days ( not miles ) and it seemed fine!! Till it did the same thing tonight!! I took a plug out and it was soaking wet and black!! I put a lighter on the plug and set alight to it and held it burning!!

I was told when I first picked the car up from the last owner that it had just been rebuilt!! As you never know what's the truth, but the engine does seem like it's been rebuilt with nice new shiney heads and new gaskets everywhere. The car has spent most of it's life abroad.

Has anyone had this problem???

Its driving me crazy!!

[Hybrid_From_Hell]

It sounds as if it is hugely overfuelling - HUGELY

This can and does kill plugs, but I have never ever come across a once use set overfulling

Anyways, when you do drive it how does it drive ?...perfect or maybe as though you had

the "Choke" pulled on, does it belch smoke when you boot it, if you stand at the back near the exhaust

dopes it stink of fuel ? whats the MPG like ??? ...if yes thaen thats a clue to over fuelling

You need to maybe start at the basiscs, 1st I would check the fuel pressure in the fuel rail to ensure the PRV

(PRV = Fuel Pressure Regulator - gold coloured tubey thing ) hasn't gone on holiday,

overpressuring this way will cause havoc with massive overfuelling.

Then check the ECU fitted is the correct version for the engine number, same with the AFM

If you can borrow known good AFM PRV and ECU, if you haven't already chage the CTS sensor as this can also cause mass overfulling

We prob need more info to sort, but the above should be a start for you

also see the tech diagnostic guide I shoved in the tech forum for a hotwire

and work through ALL the tests and then report back

Nige

Oh and PS - Fill in your location - you never know which forumeer could be near you

[gazzer]

I had a simillar problem with over fueling last year and it turned out to be the fuel pressure regulator. Mine would run for about a few hundred yards then loads of smoke then stop. It cost about £30 and it was a bugger to fit as it sits betwwen the bulkhead and the rear of the engine.

[Alistair P]

Concur with Nige ref overfueling being the problem and with his list of things to check, particularly the CTS.

You might want to read the article at the following link http://www.britishv8.org/Articles/Rover-14CUX-EFI.htm as it contains a useful description of the main components making up the hotwire injection system.

Some other things you should check are as follows:

1. What milage has it done? As A K reg I am guessing in excess of 100K. Have a look at the cam (and the valves and valve seats whilst you are at it) and see if you have rounded lobes on the cam. It could well be that if the engine hasn't ever had a rebuild. If this is the case, your cam shaft will be knackered which could result in these problems, particularly if, as you seem to indicate, the problem apparantly diminishes when the engine is hot. The Rover V8 has an amazing ability to carry on just about working with an inconceivable amount of cam wear, and replacing a worn cam will greatly improve fuel economy and performance.

2. Throttle position sensor. This is one of the most common failure points (the wiper arm on the resistance track inside gets knackered) and is easy to diagnose and (relatively) cheap to replace. See the advice at http://www.v8engines.com/carbs-2.htm#setting-up for a simple resistance check to see if your throttle pot and air mass meter have the right resistances and operation.

3. What is making the alarm bells go off for me is that (like my modified Disco V8) you say that your car has no cats Assuming your vehicle was UK market (and the age related plate is correct), it definately would have done when it was built. This means that someone has stuck an aftermarket exhaust on it with the cats removed, e.g. the performance exhausts supplied by Rimmer Bros. This is Not a legal problem as yours is a K reg and it only became a legal requirement for cars to have cats from late 94 onwards.

Importantly, what you don't mention is whether or not you still have lambda sensors fitted to both the exhaust down pipes. Do you have lambda sensors fitted?

Your vehicle would have originally had lambda sensors fitted from build. It does not however strictly need them to run in that it will run without them... if however they have simply been removed without further modifications to the wiring loom, it could make your engine run very rich. I would also expect your 'check engine' light (orange light top left of dashbord display) to be on registering a fault.

Is this check engine light on? (Bear in mind when you disconnect the vehicles battery you will reset this light and it may not come back on again until the car has been run some miles on the road). If it is on, you need to get the fault code read as this will almost certainly indicate what the problem is.

In any event, a 'Tune Resistor' was originally specified in the wire harness so that one ECU could serve multiple vehicle markets. (Multiple computer programs could be stored within the ECU, and the ECU could "decide" which one to use based on what resistance it sensed.) One leg of the Tune Resister was wired to terminal 5 of the ECU, and the other leg was spliced to ground. If your vehicle originally had lambda sensors, it would originally have had a White tune resistor (3900 Ohms USA and European vehicles with catalytic converter). In the unlikely event that your vehicle cam from the factory without lambda sensors, it would have had a Green tune resistor (470 Ohms UK and European vehicles without catalytic converters) or alternatively a Yellow (910 Ohms Saudi vehicles (without catalytic converters)). If the vehicle is a 'grey market import', e.g. from Japan, it may have a Red tune resistor (180 Ohms Australia and "the rest of the world).

What you need to check is the colour / resistance of the tune resistor. If you have no lambda sensors fitted and a green tune resistor, you are running correctly and the check engine light will remain off. If you however have a white resistor and no lambda sensors then your ECU is applying the wrong fuel maps and your check engine light should come on after a period of running. Go and buy a green resistor from your local dealer and swap it.

4. Are all your spark plugs coaking up equally? If not, then it could be that you have one or more knackered fuel injectors which may be sticking open. You can get these ultrasonically cleaned relatively cheaply to improve the fuel flow through them.

Alistair

[Ally V8]

May be worth checking that the fuel temp and coolant temp plugs have not been swopped,seen it several times and it causes massive overfuelling when warm.

[SteveRK]

If the engine ECU is for the later Lambda sensor model and Lambda sensors are not fitted (you say it doesn't have cat's) then check that the correct 'resistor' is fitted to the ECU. Cant remember the colours used but green and white are for vehicles dependant on whether cats are fitted or not. The resistor is found in the vicinity of the ECU loom and may be taped up to the loom. It is encapsulated in a clear plastic shroud. The 'colour' relates to a part of the shroud, not the actual resistor itself that is a standard colour coded low wattage resistor.

[ramon alban]

Hello Cookies,

Your Efi system is overfueling so you have to test all the components and wiring connectors that could cause that.

Coolant temp sensor, throttle position sensor, Fuel pressure regulator, weeping injectors, malajusted AFM and broken ECU.

If this thing came on suddenly then bear in mind that the vast majority of ancient Rover faults are due to air leaks into the plenum and wiring faults.

Overfuelling is not generally caused by air leaks so concentrate on testing for connection problems and mentioned component faults before buying loads of unneeded spares for undiagnosed problems.

Althought NOT written for your system you may find some useful component/wiring testing assistance here:

http://www.vintagemodelairplane.com/pages/...mponents01.html

and elsewhere on the same site.

Alternatively I believe there is a general RR document called RAVE which may assist.

Ramon

www.vintagemodelairplane.com

[FridgeFreezer]

If this thing came on suddenly then bear in mind that the vast majority of ancient Rover faults are due to air leaks into the plenum

You've posted that line a few times, I'd have to say I've not found air leaks to be a common thing with V8's - it's almost always an electrical fault, either dodgy sensor, naff ignition, or a good old wiring fault.

Over fuelling seems particularly unlikely to be related to an air leak - IMHO suspect #1 is the coolant sensor, closely followed by the fuel pressure regulator and the airflow meter.