P38 idling rough and cutting out

Hopefully somebody can help me out with a problem on my p38 4.6.Drove it on Saturday on an hour and half trip, left it standing for 20 minutes and when I went to start it it spluttered and then kept cutting out (fuel or air problem). The idling got progressively rougher and it cut out after a couple of minutes.I couldn't keep it running, everytime I touched the throttle it spluttered and died. Got it relayed home (after 8 hours of the AA sending out power lifts to relay me!!!!). Started it yesterday and it was fine, drove it all day and never missed a beat, only thing it is is ticking over slightly roughly.Anybody got any ideas. My worry is the problem will come back, when I least want it.Thanks Daz

Hi Daz,
You need the engine management system scanning for fault codes.

Nige

Rangey is currently in the main dealers and they can't get any codes out of it. They have changed the Air flow meter checked the manifold for cracks and can't find the problem. It has had a full compression test, all the plugs, leads and coil pack are fine. Anybody please have any ideas, i'm running out of money and options. It will idle very roughly and will drive a hundred yards or so at a max of 2500rpm, then it will splutter to a hault.
Please help.
Thanks Daz

Hello Daz, Observations in RED

Daz said:

Rangey is currently in the main dealers and they can't get any codes out of it. They have changed the Air flow meter checked the manifold for cracks and can't find the problem. It has had a full compression test, all the plugs, leads and coil pack are fine.

All good because there is actually nothing wrong with the system.

It will idle very roughly and will drive a hundred yards or so at a max of 2500rpm, then it will splutter to a halt

With no proven system problems, how about crud in the fuel tank, fuel lines, pump, filter and elsewhere (injectors?).

The fuel supply companies are pretty keen on additives to keep our engines clean these days, perhaps they are so good they clean the crud from the inside of fuel tanks too!

If so, the result is inevitable.

Click to expand...

Ramon
Vintage Model Airplane and Rover SD1 3500cc Twin Plenum Vitesse

Thanks Ramon, makes a lot of sense and explains why no fault codes. I will try and clean the fuel system with a compressor when I get the car back.
The main dealers seem to have very limited knowledge of the P38 so forums like this are extremely useful. Thank
Daz

Daz said:

The main dealers seem to have very limited knowledge of the P38 so forums like this are extremely useful. Thank
Daz

Click to expand...

brilliant.. flagship model for how many years?????

Daz said:

The main dealers seem to have very limited knowledge of the P38 so forums like this are extremely useful.

Click to expand...

Hello Daz,

Amazing isn't it? I have never owned a RR, never worked in a garage, never serviced my own cars before I retired and have only electronics as a background, and yet the dealerships, who employ folks to service cars, cant come up with some simple logic, that if the ECU says there are no faults in the electronics system then it might JUST be something else.

God help the country when all us ancient engineers are dead and our children are left totally at the mercy of diagnosis by computer.

Bring back engineering colleges and apprenticeships!

Ramon

got the car back last night and the dealers admitted they were stumped. Got some read outs with a couple of codes eventually. Got a P1178, P0102 and a P0103. They reckon they tried 3 different types of air flow meters on it and the problem never disappeared. Is there anybody in the gloucester are who would be prepared to have a look for me? I will happily pay the going rate to somebody who knows more that the dealership does.
I will blast the fuel system with the compressor today and see if that helps.
Thanks
Daz

sorry guys bear with me. If I disconect the air flow meter should I notice any difference in the running? When I unplug it I get no difference, does this point it being the problem?
Thanks Daz

dont think you will see an immediate result, if you take out the spark plugs how do they look(thats like a doctor looking at yr throat, dealers don't do it that often!!!) it could be that the HT leads are breaking down under load. i know no test for this. if it were me i would clean the fuel system and chuck some new leads and plugs on it

old farts are not dead until in the box 6ft under, items needed to check spaky leads if breaking down, go into the kitchen when wife is not about take out 1 surface spray bottle from under the sink, tip contents down the plug hole, (no wife about) fill with water,start engine spray a tiny bit of water on 1 lead at a time and rev engine if leads are breaking down the water will cause tracking and misfire, but dont spray on the dissy cap.easy test on dissy cap, remove cap wipe inside the cap with wd 40 wipe dry and the get some chalk dust sprinkle all over inside of cap then blow out the dust with your mouth any tracking in the cap will show up with the chalk, then go and explain to wife where the contents of bottle you used have gone to,

Cheers for the replies. I have now eliminated fuel as the problem, I have new plugs and leads on it and still have the problem. I have ordered a new Air Flow Meter and Throttel Potentiometer. Heopefully one of those will help.
The plugs were a little balck but not execessively. Can't find any leaks in manifold or any of the air pipes.
I appreciate all the responses and would welcome anymore thoughts anyone has.
THanks
Daz

Hello Daz, observations in RED

Daz said:

I have now eliminated fuel as the problem,

You mean fuel supply? Yes?

I have new plugs and leads on it and still have the problem.

Did the main dealer put the new stuff on, and leave them on despite, the problem not being fixed? Licensed to print money, they be!

I have ordered a new Air Flow Meter

I recall you saying that the AFM had been changed a couple of times. Did that exercise identify yours as the source of the problem?

and Throttel Potentiometer.

The TP can be readily tested for over fuelling characteristics so it could be a good call if you know its faulty.


Hopefully one of those will help.

The plugs were a little black, but not excessively.

A "little black" is still wrong which indicates overfuelling. However, intermittent sparks might result in similar symptom.

If overfuelling be the problem then there are some other components that would come under suspicion. Temp Sensor, Pressure regulator and ECU.

Stay vigilant when going thro the test processes.

Can't find any leaks in manifold or any of the air pipes.

Thats great and it supports the situation that the engine is running rich, not weak.

I appreciate all the responses and would welcome anymore thoughts anyone has.

Keep the faith, and keep the questions coming, eventually you will find the prob.

Click to expand...

Ramon
Vintage Model Airplane and Rover SD1 3500cc Twin Plenum Vitesse

anybody know how I test the TP?
Cheers
Daz

Daz said:

got the car back last night and the dealers admitted they were stumped. Got some read outs with a couple of codes eventually. Got a P1178, P0102 and a P0103. They reckon they tried 3 different types of air flow meters on it and the problem never disappeared. Is there anybody in the gloucester are who would be prepared to have a look for me? I will happily pay the going rate to somebody who knows more that the dealership does.
I will blast the fuel system with the compressor today and see if that helps.
Thanks
Daz

Click to expand...

If its still not sorted send me a PM and we can work something out.

Daz said:

anybody know how I test the TP?

Click to expand...

Follow the Throttle Pot link from this index and open the PDF for the full Monty.

Also loads of other test processes for Efi components.

Some will apply to your car.

Rover SD1 Efi System Components

ramon
Vintage Model Airplane and Rover SD1 3500cc Twin Plenum Vitesse

Right I have now changed the following and have no improvement :-
New Crank Sensor
New Plugs
New TP
New Air Flow Meter
and the dealers tried a new ECU in it.
Any ideas?
Thanks Daz

Hi Daz
Have you sorted out this problem yet?

Regards Craig

HI, IF YOU STILL HAVE YOUR P38..CHECK THE WIRES THAT GO INTO THE THROTTLE POSITION SENSOR..I HAD SIMILAR PROBLEMS WI MINE..
AND A MEMBER GAVE ME THE ADVICE (ITS ONLY 3 WIRES) GET THE PLUG OF A ROVER 800 OR SIMILAR ..PLUG IS NUMBERED 123
GOT TO BE WORTH A TRY..MINES RUNS BETTER THAN EVER NOW:beer2:

All thanks for all the help and I have now resolved the problem. Brand New Air Flow meter didn't sort the problem,then put a new TP on and no improvement. Put the old AFM back on and the problem had been fixed. So the TP was knackered and the main dealers couldn't identify it.
I'v now sold the car and bought a V8 defneder on carbs, so no horrible high tech worries for me!!!!!
Soon be posting with questions on that one.
Thank Daz