Solution to Engine Misfire =>1996 Disco's

[Mark]

WillieGA-

Not disagreeing on the final diagnosis, but you were not that specific on the mis-fires codes.

So far, I have determined from this post and other forum posts that misfires of #7, occasionally #5 may very well be the VSS, as it was in my case.

But you are stating that misfires were occurring on more than those two cylinders or am I reading too much into the post. How did you determine the 4 cylinder result? With codes?

Also, did the VSS get replaced and what miles are on your Rover?

My summation:
Misfire on #7 -- VSS
Misfire on #7 and #5 -- VSS {maybe the O2 sensor is starting to fail}
Misfire on the remaining odd cylinders -- O2 Sensors.


Comments anyone?

 

[Williega]

Mark,

I did change the VSS, as you suggested (thank you for the instructions), but after it continued I had to get the mechanic involved.

Yes, the misfire codes were pointing to multiple misfires and misfires on cylinders 2 and 7. As far as I understand it, when you get more than one cylinder misfire code, you also get the multiple misfire code with it.

The mechanic determined the truck was running on four cylinders after testing the engine and the computer.

And yes, he also replaced all 4 02 Sensors.

My Disco has 62k miles.

 

[Mark]

WillieGA,

After I saw the VSS fall apart on the floor with the cheap construction, I realize that all original VSS's should be changed, regardless.

Thanks for the info about the misfires, that is very informative.

 

[etrnly]

WillieGA,

After I saw the VSS fall apart on the floor with the cheap construction, I realize that all original VSS's should be changed, regardless.

Thanks for the info about the misfires, that is very informative.

That dosent sound like a bad idea, Where can I find a good deal on a VSS for my 96 Disco?

Thanks

 

[Mark]

Check Rovers North, Altantic British, Northwest British, etc. Get the catalogs, very informative.

 

[ericksd]

Hey everyone,

Thanks for all the info so far, it has been pretty useful.

I have a 99 D2 4.0.

I am also having alot of trouble with misfires from # 7, but I don't think it is the VSS.

I have a Rovacom diagnostics setup and can monitor all cylinders while it is idling in the driveway. Among other things, the particular page I had pulled up on my laptop displays the roughness and number of misfires for each cylinder.

All other cylinders seemed OK with only a little roughness here and there and no misfires (with the exception of #7).

When the Service Engine light came on 2 weeks ago, I checked the codes and it told me I had the misfire on #7. I have used the Seafoam a few times before, so I used it again hoping it would help, but so far it has only seemed to have gotten worse.

I have used the Seafoam in the tank and oil once, and through the intake twice. The oil was changed about 200 miles after the Seafoam.

I have swapped plugs as well as wires and the misfire stays with the cylinder.

I have done a compression test and all cylinders were pushing an average of 150 PSI except # 7, which was only 95-100 PSI. It seems that #7 is not sealing at one or both valves.

It seems to me that anything like an O2 sensor or the MAF would be causing misfires from multiple cylinders (which I have had codes set for that, but thought it was from choking the engine with the Seafoam). I could try swapping O2 sensor with the one from the other side, but I kinda doubt that would help with the misfire that is just on #7.

In all the reading I have done so far, I understand that Seafoam or other treatments will not work on the exhaust valves because by the time it reaches them, it is already burnt and no longer a liquid. With all the Seafoam I have used and still the misfire, I am thinking it is an exhaust valve.

If a cylinder is misfiring, wouldn’t the Seafoam or other treatment reach the exhaust valve in a liquid state?

Should I try a different treatment like the B&G 44K, or just keep adding the Seafoam?

A drag racer here at work, told me he sometimes slowly squirts water into his intake and it steam cleans the crap out. Not sure this is a good idea, just wandering what you guys thought about it.

I’m not opposed to taking the heads off to do it the right way, I just was wondering if there was something else I should try.

Any Ideas?

 

[Mark]

Does your Rovacom read vehicle speed?

I found that when #7 was misfiring, the Actron Computer was reading 115 mph, while the tach and speedometer were flickering.

With the misfires on the odd cylinders, my driver side O2 sensors are almost if not shot. The passenger side O2 sensors are vibrantly bouncing back and forth gleefully doing their job, while the driver side seems stuck on RICH when sitting at the light, and lean when driving.

My case was purely the VSS, it came apart before it hit the floor. I think the reason a code was not thrown (MIL) is that a valid signal was leaving the VSS and being received in the computer. On occasion, no connection to anything, the misfire codes would occur. It was with my scanner that I found my problem.

Except for the 150 psi test, I did everything else and found the VSS the culprit.

 

[ericksd]

Does your Rovacom read vehicle speed?

I think so...I will check.

At least on my D2, I thought that the VSS is what drives the speedometer.

If your device showed you going that fast, would'nt the speedometer also show the same?

I have never noticed my speedometer wigging out.

Initially, I did not think it was the VSS, because I was seeing misfires and experiencing rough idle while it was parked in the driveway.

I have since noticed that the SES light comes on when accelerating from a stop (or this morning) going downhill with my foot off of the accelerator.

I'm thinking now that maybe it COULD be the VSS.

I'm also thinking of replacing the MAF. I noticed that sucking the the seafoam through the vacuum hose last time around, puked some of the seafom onto the MAF (not sure how it did that because the butterfly would/should have been closed at idle) Even though I have cleaned it a few times, I'm just wondering if is time to just replace it.

I am going to pull the air inlet manifold this weekend to replace the coil pack and plug wires.

While I'm in there I will probably pull the valve cover and valve springs to see it the valve is seating properly (like the Robinson writeup referred to at the beginning of this thread).

I guess if none of that works, I will look at the O2 senosrs and the VSS.

SES light was blinking today on the way to work. I have read somewhere, that this means I am melting the CAT.

HOLY CRAP!!!!

Dan