Solution to Engine Misfire =>1996 Disco's

[Williega]

Team,

After spending lots of money and going through the guessing game, I came across this article, which diagnosed exactly what my Disco was having.

It is EXPENSIVE, but after you have replaced your spark plugs and wires, fuel filter and coils or coil packs, and still getting single cylinder and multiple misfires, this should be your final solution:

http://www.robisonservice.com/servicedep/pdfs/carbon_fouling1.pdf

 

[meyersd]

That is exactly what most people are trying to avoid... That should be your last resort, if that can of Seafoam doesn't do the trick...

 

[Williega]

Team,

I am not looking forward to have my mechanic stick me with a $1,000 bill to take the engine apart and clean the exhaust valves.

I already put the Seafoam in the intake hose, oil and fuel and I still have the misfires.

Any other way to get the exhaust valves cleaned?

Thank you,

 

[Mark]

Vss

Having gone through the same issues, mis-fire on cylinder 7 and occasionally 5, I also sought out an answer.
The solution was a screwed up VSS (Vehicle Speed Sensor). Replaced in Aug and the engine runs like a bat - out - of hell!.

When the mechanic took the VSS out, it fell apart before it hit the floor.

LR wanted to know how I thought it was the VSS and not something else, like a valve job.

the easiest part of the question is the Actron scanner (9145) that I had attached and when the misfire started, I would scroll up and down the screen looking for something erratic. I finally found my vehicle speed rising to 115 mph and I was doing 55mph.

Then I would check the code that was thrown and see it was a misfire on #7.

For $100 try this first. I think it is a cheap way to check and in the long run, a new VSS is installed.

 

[Williega]

Thank you Mark. I am getting multiple misfires as well as specific cylinder misfires. I also heard about getting the "Road Speed Transducer" replaced to get the misfires resolved.

Do you know if the VSS (Vehicle Speed Sensor) is the same as the Road Speed Transducer?

Thanks,

 

[Mark]

Uhmmm, Never heard of that term but could very well be the same thing.


The VSS is located on the transfer case and held by one bolt and a wire plug. You will need an extension to get to it and maybe some small hands with long arms(?) That is why I went to the Rover dealer to have it replaced.

I kept the old one and played with it on the Fluke when I got home. A very simple item yet very important.

If you look through OBDII codes, you will find a code for the VSS. I NEVER threw that code since it would work and feed a signal. I think that code will only throw when it completely fails. Otherwise, when the engine is told that you are screaming down the hiway at 115mph, the engine is programmed to misfire to slow the engine down. Hence the priority in the misfire code.

Cheap repair. try it.

 

[Williega]

Mark,
My 96 engine might be configured differently. Perhaps if you could be more specific about the location (front left, right rear, under...etc) or post a picture/drawing. Then I can switch it and see if that solves the problem.

I don't know where my transfer case is or what it looks like.

Thanks,

 

[Mark]

Vehicle speed sensor

The vehicle speed sensor is located on the transfer

box behind the transmission brake. The unit has a

multirole as the vehicle electronic speedometer

sensor and as a sensor for ’surge damping’, (a

function which smooths out engine response to sharp

accelerator movement and reduces vehicle ’bucking’).

The sensor is an additional input for engine overheat

protection.

 

[Moose]

Use two 6" 3/8" extensions, a ratchet, and a 3/16" Allen driver to get to it. It's super-easy to DIY. Just make sure the square drive in the VSS fits into the square socket on the transfer case.

 

[Williega]

Thank you everybody for your imput.

My problem turned out to be bad 02 sensors, which were sending bad signals to the computer and caused it short out. The computer in turn put itself on safe mode running on 4 cylinders and causing the engine to misfire. All this misfiring caused my Catalytic converters to run hot and go bad.

I was fortunate not to have bad exhaust valves on top of this. I got most parts after market so the deal ended up being around $1,500.

On the road again.