Discovery 1 running rough when warm

[rickl]

Hello All

I have a 1997 Discovery 1 3.9 and until recently it was running well. I put the car in for a rego inspection and since it has become a dog when the engine is warm. It appears the engine was pressure cleaned but I am told nothing else was done.

About 2 months ago the fuel pump died and a new one was fitted but the car ran fine since then. Ever since I got he car the idle speed has hunted when the car was warm.

The car starts and runs fine cold. On warm days or when the engine gets warm and under load it starts to lose power. The first sign is the engine will not rev past 3000 rpm. It soon starts to backfire and keeps losing power until it will not even run.

I was told that it was likely to be the coil or ignition module damaged by the engine cleaning. Both have been changed and it has made no difference. When I was changing these I noticed the wiring near the radiator, for the coil and the ignition module, looked dodgy so I cleaned all the connectors.

I have found that I can make the car lose power and start backfiring by having the air conditioning on. I am assuming this is because of the increased load on the engine or the more under bonnet heat produced.

I have found that if I open the bonnet and let the car cool for only 15 minutes it will run fine again for a while.

I am starting to tear out my hair as no one has been able to give me any useful advice on what to look at.

I would appreciate any advice on what to test as the car is unreliable as it is.

Regards

Richard

[Traco]

Check the rotor and dissy cap, plug leads and plugs themselves. Could also be an air leak, check around plenum and tightness of inlet manifold bolts.

Other culprits could be AFM and possibly TPS. D1 autos also suffer from sticking valves if driven lightly on ULP. Let tank go down to nearly empty, chuck in a bottle of Nulon FI cleaner or equivalent and take it for an Italian Tune up - i.e. rev it to 5000 rpm in lower gears (or manual shift the auto box). Afterwards fill it up with premium and if an auto drive it round the city in 3.

[cockie55]

You don't say you have overheating problem so in addition to Traco's advice I would also look at overall timing particularly as symptoms of power disappearing at 3K is also reflective of a seized mechanical advance.

[bee utey]

I would take the terminals off the coil one by one, tighten, and refit. A loose terminal complete with a bit of corrosion will do that. Also take the cap off with the engine warm, look for condensation.

[mike 90 RR]

I'll add some real simple checks.....



Suck on the Vacuum advance unit and see if it holds vacuum

In total darkness .... Lift the bonnet and start the car ... You will instantly see any ignition Sparks Arcing out from the leads & coil / cap

Start the car & pull the plug on the MAF .... Go for a drive



It'l be something silly ....

Mike

[nzlandies]

The temperature sensor in the middle of the V is know to cause issues. Might even be loose. cheap to fix. That is where my money is.

[rickl]

Hi All

Thanks for all the tips. Over the weekend the car has gotten worse so I am now getting desperate.

The car will no never rev past 3500 in neutral. I can start teh car and from cold it will not free rev past 3500. As the car gets warm or the air temperature rises the car will not free rev past 2500.

Under load the car will not rev past 3000 even when cold.

I have found out that the other driver of the car has been putting E10 fuel in the car for a few months. I usually use Premium or just ULP when I can't get it. I am not sure what E10 will do to the car though as the compression is so low on D1's.

I have tried the following this weekend with no improvement noticed.

I put a bottle of Nulon injector cleaner in half a tank and ran it to empty. I then put a full tank of Caltex Vortex Premium ULP in and have so far run through half a tank. All I have noticed is slightly better idle and better fuel economy.

I have looked at the engine in complete darkness when it was misfiring and can see no signs of sparks around the coil or distributor.

I have checked the rotor button and distributor cap and both look fine with only minor burning on the cap contacts. Both are about 5 months old.

I have checked all coil wiring and cleaned all connections and all are fine.

I checked the vacuum advance and it is holding vacuum fine. When vacuum is applied I can see the baseplate moving. I checked the bob weights were not stuck and they seem fine and free.

I checked the static timing and it was 6 degrees. I can't see how this would have just changed from when the car was running fine.

I tried unplugging the MAF while the car was idling and it almost stalled. The car could not be driven with the MAF unplugged.

I checked the voltage going to the coil and ignition module while driving and they sat solid at 13.9 volts even when the engine was misfiring. I had heard of an alternator fault causing misfiring so it was worth a check.

One rubber boot on the coil lead looked a bit sad so I tried another coil lead.

I checked the other leads and they looked fine. All measured OK for resistance.

I pulled the plugs and all seem to be burning fine.

I am at my wits end with this car.

I would appreciate any further thoughts on trouble shooting.

Regards

Richard

[bee utey]

Fuel pressure. I can't help you with specifics but if you can read fuel pressure before the regulator, it is a good diagnostic for fuel delivery problems. I have made a tee for a different vehicle once, you are looking for a rise under load as the manifold vacuum drops. It is probable that your fuel pump has a pressure leak, especially if someone has repaired it. Perhaps also regulator problems. Pinching closed the return hose will raise pressure if the pump is OK, do this carefully and listen to the engine.
The fuel pump is quite easy to access, lift the cargo area mat and unscrew the hatch. Remove the pump and check for loose/ split pressure hose.
Someone else posted about an ECU that they changed fixing his running problems, find an owner willing to swap, ask here if there are any problems with that first.

[lokka]

I had a similar prob with my 95 3.9 disco i ended up replacing all the ignition system dizzy coil amp leads the whole lot got canned and in went the crane system from my old rangie and what a difference it made no more prince of darkness for my disco :D

[nzlandies]

Its fuel related, not spark. When engine temp rises it goes lean and backfires because exhaust is too hot. Why does it go lean when hot then. Temp sensor #1, fuel pressure reg #2. After you stop and temp drops a bit then the cold start valve probably gives enough fuel to run for a bit or the temp sensor leans the mixture out.

[Utemad]

I had similar problems with mine. I pulled my hair out looking for the cause. Turned out it was the new aftermarket rotor button.
Started running rough on lpg first and later it did it on petrol. Ran fine for months with the Bosch part so even though everyone said to swap it for a genuine one it took me a while to do so.
So fit a genuine one if you haven't already $45 delivered from Karkraft.
Alternatively ask Beeutey for the Ford Bosch part that fits.

[bee utey]

I had similar problems with mine. I pulled my hair out looking for the cause. Turned out it was the new aftermarket rotor button.
Started running rough on lpg first and later it did it on petrol. Ran fine for months with the Bosch part so even though everyone said to swap it for a genuine one it took me a while to do so.
So fit a genuine one if you haven't already $45 delivered from Karkraft.
Alternatively ask Beeutey for the Ford Bosch part that fits.

GB864

[rickl]

Hi All

I changed the coolant sensor this morning and it made no difference at all.

I would be surprised if this was the problem because the problem is now happening when the engine is cold. As I mentioned last night the engine will not free rev past 3500 when cold now.

As I first mentioned the car had a new fuel pump about 2 months ago. I cracked the fuel connector on the injector rail and the pressure seems quite high although I don't have a fuel pressure gauge to get a pressure reading.

The car also had a new fuel filter when the pump was changed.

Is this still sounding like a fuel problem?

Regards to all who are offering suggestions

[bee utey]

Hi All

I changed the coolant sensor this morning and it made no difference at all.

I would be surprised if this was the problem because the problem is now happening when the engine is cold. As I mentioned last night the engine will not free rev past 3500 when cold now.

As I first mentioned the car had a new fuel pump about 2 months ago. I cracked the fuel connector on the injector rail and the pressure seems quite high although I don't have a fuel pressure gauge to get a pressure reading.

The car also had a new fuel filter when the pump was changed.

Is this still sounding like a fuel problem?

Regards to all who are offering suggestions


It is not unknown for replacement pumps to fail quickly, or the hose to burst inside the tank. It should be possible to fit a tee piece and a pressure gauge, the turbo boys frequently fit adjustable regulators with gauges. I bought one on ebay for not very much to replace a failed Volvo regulator for which I didn't know the design pressure.

Not withstanding the pressure problem, how does it run under light load? What about low RPM and acceleration? If it splutters under load then it could be a failed coil, that is common enough to warrant repeat mentions.

[rickl]

Hi All

The car runs fine under light load and acceleration is as good as it always was until it hits just over 3000 rpm and then it starts to misfire. As it gets warm it gets worse

[nzlandies]

Vacuum leak? It really sounds like its not getting enough fuel or it may be the inverse in that its getting too much air, either way its too lean. Like you say it was running fine before so I doubt its some major failure and more a simple sensor or pipe is at fault.

[bee utey]

Vacuum leak? It really sounds like its not getting enough fuel or it may be the inverse in that its getting too much air, either way its too lean. Like you say it was running fine before so I doubt its some major failure and more a simple sensor or pipe is at fault.

Vacuum leak will cause poor running at idle, from what you say I would say fuel delivery rate is a problem. Take your fuel filter off and see what is in it after 2 months. Just let it drain backwards into a clean container, shake it a bit. If you see lumps they have been through your pump. If its clean then the pump is probably OK. Was it a genuine pump? Maybe its too low a volume aftermarket thingy, as it wears it gets worse.

[rickl]

Last night I tried the suggestion of pinching off the vacuum line to the fuel pressure regulator. This made no difference I could detect at any point in the rev range.

I will try the fuel filter tonight as I have a spare new one.

[bee utey]

Last night I tried the suggestion of pinching off the vacuum line to the fuel pressure regulator. This made no difference I could detect at any point in the rev range.

I will try the fuel filter tonight as I have a spare new one.

Removing not pinching the vacuum hose will raise the pressure if it is operating. In any case, no vacuum equals full power setting.

[rickl]

Hi All

It looks like it might be fixed. I changed the fuel filter last night and it is running fine now.

I could knock any rubbish out of the filter so I cut it open. I found a lot of black sludge in the filter.

Before I installed the new filter I ran a few litres of fuel into a bucket to see if there was any more junk in the fuel and it looked fine.

Thanks to everyone who had ideas for me to try

[muddy69]

Rickl,

You beat me to the crunch. All the symptoms you mentioned were the same in my case and wouldn't rev beyond 3500k for me.

Changed out the fuel filter....wow the power was restored.....

Sorry couldn't get in earlier to help you with the problem.

I changed fuel filter at same time I changed out my faulty fuel pump.

Muddy

[rickl]

Hi All

Well it was too good to be true. After a few days of running reasonably well the same problems are back. I have checked the new fuel filter and it looks fine. I actually had another new filter on the shelf and I tried fitting that but it made no difference this time.

I pulled the fuel pump out last night. I had this pump installed a little while ago when my pump just died and I was in a hurry to get the car going. I have no idea where the mechanic got this pump but I am a bit concerned about the way he has installed it.

For some reason he has replaced the factory fuel hose on the output of the pump. The hose he has used is a black rubber hose marked as safe for submersion in fuel. He has used a hose clamp on each end of the hose. The new hose is no where near as flexible as the factory hose and seems to be pushing the pump down.

Is it possible that the installation of the fuel pump could be causing my problems? Without a fuel pressure gauge is there a quick way to see if I am getting the fuel pressure and/or volume I should be getting?

Is it worth just biting the bullet and getting a new pump?

Regards

Rickl

[PhilipA]

The hose should have no effect as long as it is the corect length. The OEM is very flexible to allow the pump to rise if the tank gets a clout. You will notice the whole assembly is on sprung columns.

The filter sock will have notches in the input to the pump.

Just check that the filter sock does not have any splits as this happened to me in NT. Some fluffy stuff went through the split and the car would go well for 15 minutes then take no accelerator. Stop and the whole process would repeat. It was that the fluffy stuff was blocking the inlet pipe of the pump, then would fall out as I stopped the engine.And so on ad infinitum.

I flushed the tank and finally as a last resort in Mataranka pulled out the luggage and changed the pump. Later looking at the pump I pulled out I saw the problem. AGGGGGGGH!

Regard sPhilip A

[rickl]

Hi All

At long last the dramas are finally over and the car is running fine again. The problem turned out to be the fuel pump. More correctly the dodgy mechanic who replaced the fuel pump a few months back when it failed one morning.

The guy had dropped the rubber fuel sender sealing ring inside the fuel tank and had used black silastic gasket to seal the sender unit to the fuel tank. he did this because without the rubber ring the lock nut could not tighten down far enough to hold the sender unit. To make things worse quite a bit of silastic was inside the tank.

When i pulled the pump out I noticed some black muck on the outside of the prefilter but thought it was just sediment in the tank. The tank was very low on fuel and i noticed some lumps of black stuff inside the tank. I soon discovered they were dissolved silastic.

I checked the new fuel filter I only installed a week or so ago and found it to be blocked. When I cut it open I found this black muck inside it. I flushed out the fuel line from the filter to the pump and there was a little muck in there. I spent a few hours cleaning the entire fuel system.

I decided that the muck must have gone through the pump to get to the filter so I installed a nice GOSS $75 VN Holden Commodore pump and put the whole thing back together. I put the rubber ring back where it was supposed to be.

Surprise the car runs just like it should. The poer is what I was used to before all the trouble started and the fuel economy (yeah right:cool:) is back to where it was.

The lesson I have learnt is to not trust a service station mechanic who tells you he has never touched a Land Rover before. It would have been much less of a hassle in the end to get the car towed to someone who knew a little about Land Rovers or basic workshop practice.

Thanks to everyone who offered idea and support while I was tearing my hair out.

Best Wishes

Rickl

[PhilipA]

AFAIK the syetem on Land Rovers is exactly the same as on Commodores and numerous other cars.
He was just a lazy ignorant robbing SOB who had no excuse for his action.

Regards Philip A

[d2dave]

Great stuff silicone except for where petrol is involved.

Dave.