Thread: Disco running rough.

Originally Posted by Dodes

Hey guys,

I'm after a bit of help with my 2003 D2 V8.

The probem I've got is it wont hold a steady idle (less than 500rpm)and it runs rich, very rich.

It all started about 2 months ago, I went to take off from a rolling start, gunned the throttle, the engine reved as it should then it sounded like the engine cut for a split second then went again, I thought this was a bit weird but then every felt normal again so didn't think much of it till I pulled up at the next red light and noticed my taco was only showing about 300-400rpm (close to the first line on the taco after the zero mark) which is way too low and was running rough. When I got the car home again I inspected everything and noticed one of my O2 sensors had been resting on the hot exhaust and burnt through the wires.

I've since replaced the O2 sensors and reset the computer and its still exactly the same. Not too long ago I replaced the ignition coils, plugs, leads, alternator, cam angle sensor and MAF.

Any help would be greatly appreciated.

Cheers,
Albert

Have you tried disconnecting te MAF and seeing how it runs. With it disconnected the ECU will simply see that its not there and determine the air fuel mixture via the other sensors and pre-determined values. Be aware it will log a fault code and turn the engine warning light on.

Another common cause of rich mixture all the time is a faulty coolant temp sensor. If faulty it will send an incorrect value to the ECU, eg if the engine is hot and it is sending a cold temp value it will run very rich because it thinks the engine is cold and need to run rich for a cold start so to speak.

Do you know anyone who can check the fault codes or data output for you?

That would be a good start since you have replaced all that other stuff already.

good luck

Dave

Thanks Dave,


I'll give that a go.


I have got a fault code reader, not a nanocom or anything like that but just a Bluetooth OBD reader and my smartphone. When connected with the engine running the coolant temp shows around 91-98 degrees C. So could it still have something to do with the coolant temp sensor being at fault.


Also could it have any thing to do with the crank angle sensor.


Cheers.

Faulty crank angle sensor will generally cause intermittent stalling or no go at all. Sounds like your coolant temp sensor is reading correctly. Did you try different connecting the maf?

Sent from my Motorola RAZR XT925

If electricals check out then perhaps there's an injector sticking open. If you can get a temp reading on each cylinder with an infra red gun thingo and it shows one or two noticeably cooler than the rest, then perhaps that's it. Uncommon though.

You only on petrol, no gas?

Cheers guys,


I think I may have found the fault, when the O2 sensor wire burnt through on the exhaust it must have blown fuse F2 under the bonnet. That would explain why there were so many faults showing, O2 Sensor fail, Cam angle, maf, purge control valve, even after I replaced them, but now I've got another problem, cause I've been removing my spark plugs for cleaning a few of my HT leads have broken. New leads ordered, and if all goes well should have it running again by the weekend.


Can't wait to get it running again cause I think I'm starting to get withdrawal symptoms from not being able to drive it.