95 Disco I w/ 154000. Background: I am third owner and have only recently started using premium. Prior owner did not. Recently put in Valvoline high mileage oil, prior owner used only dino. I know the fuel filter has not been changed since at least 75k and I know there has never been an induction, ATF flush, etc in that time frame either. Have replaced plugs and wires twice, I have owned since April 05. Last change of wires, plugs, cap and rotor probably Spring 07.
Lately it has been running rough, small misses, when at highway speed. If i step on down it will run great but upon letting up you can feel the inconsistencies again. It also feels sluggish but maybe they all do, only rover I have ever driven. I am now still on the first tank of premium, 89 octane ethanol blend before, and saw a marked difference immediately. However that difference has dissipated now that I am at a half tank, all the old gremlins are back. Any ideas? Sorry for the long post, i just thought the history might help. And each time i changed wires i used 7mm and i almost guarantee they are not magnecor.

 

Thank you for the history leasson, it helps us help you.
7mm is the factory wire size.
Sounds like you need a tune up, it has been almost two years.
If your check engine light is not on it soon will be with mis fire codes.

 

Have you tried a new, factory cap and rotor, not aftermarket?
How about your fuel filter?

 

Thanks Spike, would you recommend going to the 8mm or staying with the 7mm? What do i all need to get besides plugs and wires? Any particular plug?

 

Sorry Mike I was replying to Spike when your message came in. I have not tried the factory cap and rotor and the fuel filter I have i picked up from a Rover dealership. After reading some of the other posts i might go ahead and get the kit on Atlantic British.

 

You may want to check the following, based on your brief description of the symptoms:

[ul][*]idle speed control valve functioning properly, any oily / carbon deposits on the valve.[*]vacuum leaks between mass airflow sensor and the intake manifold.[*]Is the intake manifold gasket in good shape.
[/ul]Your problem sounds like a vacuum / air intake leak. Because you state that it runs strong if you floor it.

 

I have not checked anything that you just suggested. If I find some form of air leak to I tape and move on or what would you advise?

 

Sorry, the three items that I recommended would require basic auto technician skills, not an ASE Master tech L1 or anything like that, just basic understanding of intake plumbing and operation.

Do you have a local shop or a technician that you can ask to check these items for you. Duct taping a cracked air intake hose or duct is strictly a temporary fix that is not recommended, if that is really the cause of your problem.

 

Go with the 8mm, you will also need a LR cap and rotor.
DiscoMike likes the Bosch +4 spark plug I LOVE the Denso Iridium spark plugs.
You can use whatever you want.

To buld on what unimog said...if you find a vacum leak you will need to fix it.

DI's spark on every up stroke of the piston, so every compression stroke and every exhaust stroke the spark plug sparks.
When you have early signs of misfires the truck will run rough at low engine speeds, but at higher engine speeds you will not feel it.
When it gets bad enough the truck will not idle hardly at all and will hesitate at higher RPM.
After you put new plugs and wires on I would also take it to a shop and have the timing adjusted. You will need a shop who has a mechanic with no teeth and cant hear a word, no new mechanic knows how to adjust timing with a timing light.
They just do not teach that anymore.

 

Where do I find the idle speed control valve? The intake manifold and the connections look good. Would the fact that the fuel filter has probably never been changed attribute to the rough running?