Yes....the misfire.

Disclaimer: I am a total amateur/hobbyist at this. Read: I know just enough to be dangerous. You've been warned. Also, please feel free to comment and correct me as I'm sure it will be needed.

I'm starting this one for a couple of reasons:

1) I just bought a 2001 DII with P0307

2) I've spent HOURS searching and reading threads on this forum about misfires, and the lack of conclusion to most threads annoys me

3) I thought it would be a good idea to summarize the HOURS of reading to maybe help the next guy/gal out there.

So - your rover is misfiring huh? Welcome to the club, its a big one.

From my reading, there seem to be several recurring causes of misfires, leading to codes P0301, P0302, P0304, P0305, P0306, P0307, P0308, and a couple others that I'm sure someone will chime in on. All of these are fault codes which isolate a misfire to a given cylinder, or a combination of them. There is a general misfire code, (P0300?) that can also appear.

The possible causes:

1) Electrical - this basically is the combo of bad plugs/wires. Pretty straightforward, don't want to get too far into it. Just buy new ones and replace everything. I'm seeing mixed results on wire/plug choices, but I think it's safe to say that this would be a VERY good first step. It's also good maintenance in general.
*Coils* - this has been mixed reviews all around. Although they do go bad, most of the threads that mention them don't report replacing coils is either a)fun, or b) effective in curing their misfires.

2) O2 Sensors - these little guys are apparently engineered to give us headaches, and contribute to the growing bald spot on the back of my head. A large portion of the threads involving one of the above codes report back that the 02's, (pre-cat) helped or fixed the problem. Note - they are Bosch, Part number 15175. Get 'em on amazon or your local parts store, but GET THE BOSCH, not the cheap-o's. You own a british SUV, therefore by definition you cannot be that much of a cheapskate. Those of us blessed to have an Ultra-Gauge can read their inputs to determine how badly they are fried.. Those who don't have said Ultra-Gauge, and still own your rover, need to hitch up their pants and buy one.

3) Vacuum lines/leaks - these can manifest in all sorts of annoying ways, and are best dealt with aggressively. The smoke test, (search for "vacuum leak cigar") is a great one, but I have found in my years of messing with brit stuff that once one goes, just replace them all. There is a great outfit called hosetechniques.com that sells really high quality silicone vacuum hose by the foot. Pretty colors too.

4) Seafoam - a good, solvent based cleaner that will attempt to rectify the last 10 years of abuse your motor took at the hands of someone like my girlfriend, whose idea of "car maintenance" is putting gas in it. There's a good sticky on the treatment, and yes, you will fog out your neighborhood. If you have any enviro-types lurking around in Prius-mobiles, loan it to your neighbor's teenager to take for a ride. It's good, it works, and cleaner is better with these leak-prone swine in prom dress that we call our Rovers.

What's it cost?
Well, I like to start cheap. I currently only show a P0307, (cylinder 7 misfire), and will be tackling it in the following manner:

1) Plugs n wires. I'm going with Kingsbourne and NGK 7734's, because basically, the engine in these is an antiquated buick POS v-8 and fancy plugs/wires are a total waste IMHO. You just need to get a good spark at the right time, and let the rest happen naturally. I'm into mine for $42 for the wires and $19 for the plugs.

2) Seafoam - 'cause it's cheap, effective, and my neighbor drives a hybrid. $12 for 2 cans

3) O2's - oh, forgot to mention, its a good idea to bench test these with a multi-meter before getting into some hardcore "engine bay yoga". Not all mass-produced stuff works right off the assembly line. Live-n-learn...$53.57/each with free shipping on amazon.

4) If I still have them, I'm hitting the cigar rack and doing vacuum lines. All of them. A small leak has the ability to send your blood pressure through the stratosphere trying to chase it. Trust me.

**It's my opinion that if you have misfires, these should be (well, at least #1&2) your first steps to correct it. The 02's should be read with the Ultragauge you bought to determine whether or not they are bad**

Tired of reading yet??

Now - there are also many, many threads where people have done these things, and still have misfires. So what then?

Possibles, and I would check in this order:

1) Look at all your plugs when you change them - steamy fresh n clean? *headgasket time!* don't be sad it happens to the best of us.

2) Listen for a rattle from your catalytic converters. If plugged, they make MAYHEM for your ECU. Your options are to buy the insanely high rover y-pipe, or get some $50 universal cats (2" pipe I think) and weld them in. If you don't know how to weld, get on google and find a low-brow muffler shop. Usually around $150 to get it done.

3) Coils - some sadistic limey SOB placed them in a very nice spot under the hood, next to the firewall, so I'm eliminating everything else before messing with these, solely based on PITA factor. But maybe you need 'em. Do both at once, or you'll be sorry later.

And in the words of John Belushi - if all else fails, start drinking heavily.

I'll report back on this thread next week when I have completed plugs, wires, foaming, and cigar test.

You stay classy San Diego.

 

Oh, and I forgot to mention the MAF (mass air flow) sensor - it can also cause misfires if either dirty or malfunctioning. It is a little widget that tells your car how much air is coming in, so it can supply the proper ratio of fuel to get you from your garage to the parts store and back.

Clean it - use LOW PRESSURE (like 40psi MAX) compressed air and a LITTLE bit of brake cleaner. Overdo it on either of those, and you're buying a new one. My last 2 rovers got used MAF's because they were cheap and readily available in atlanta due to mass rover suicides during the summertime.

Replace it - Bosch makes it, AB sells it, or be one of Savannah's "partz vulturez" like me. Hey, I dropped $2500 on this ride, it doesn't need fancy new stuff...there's always a couple/few being chopped up in your zip code.

 

Nice summary.

Not too sure about the brake cleaner on the MAF, though. A proper MAF cleaner is available from CRC. I've never used either but that is the only product I have ever seen recommended in any threads.

Also, stick with quality wires with an 8 mm diameter. For some reason these trucks seem to be very susceptible to shorting of the plug wires. Kingsbournes seem to have the best rep, better than Magnecores which cost 4 times as much.

Oh, and if you do need to replace the coils take care of your leaking valve cover gaskets while your there.

 

I'm one of those poor suckers who tried all of the above, and a HG, and still have problems. You forgot to mention that the same evil genius who placed the coils where only small children can reach them also put security screws like the phone company uses on the MAF sensor, and put the driver side o2 sensor in the worst possible location and orientation. I have a long thread on my flailing about trying to solve misfires (not totally solved yet, but a lot of it had to do with a bad wiring harness). Also those hose clamps... Lord. Replace them all with a 5 dollar box of hose clamps from harbor freight.

Anyway thanks for the rundown. It really is nice to find an actual list. You reminded me to clean my MAF again. But I use the high dollar MAF cleaner. Oddly, a Rover cries like a little child through its codes yet the MAF can be a total paperweight and throw no codes.

Low compression and slipped sleeves or a cracked block on a cylinder can cause misfires.

Tonight, when I decided I had lost enough blood messing with the catalytic converters (also on your list) I walked in the garage and opened the hood on my 31 year old Mercedes. It is rough looking but the engine runs like a sewing machine. Staring in the engine bay I saw no plastic lines, no computers, and no nonsense. It would look so nice in a discovery ii.

Thanks again for a great post. Good service to the forum.

 

Ah yes..I also am lucky enough to own a Benz diesel. They are truly functional works of art. Mine is a non turbo, inline 6. Wonderful car.

Slower than grandma draggin a wagon.

I'm aware of the high dollar MAF cleaner, but I've just always used a very small amount of brake cleaner and gentle air. I'm sure the MAF stuff is a safer bet, but again, see disclaimer at the top.

Charlie, I'll keep updating this one, and I've read yours quite a bit. That's one of the first wiring harness issues I've personally heard of, and this is my 4th disco. I'll be curious to see how you resolve it, as you seem to be blessed with one of the more confounding cases out there.

I'd also be curious to know if anyone can shed some light on how the computer defines a "misfire", I.e. does it show a spark being sent but not a subsequent combustion stroke? A combo of several things? A timing screwup? That might shed some light on all of this.

And yes, anything you can do to stop valve cover leaks is a definite plus. I read somewhere on here that "the containment of British automotive fluids is an inexact science"....

 

You make another excellent point. I, too, wonder how the vehicle defines a misfire. When you can watch the throttle plate open, when you know the gas is flowing, and when you have tested to make sure the spark is there in a sequence, and the exhaust gases are exiting and don't smell of un burnt gasoline, I wouldn't call that a misfire, but my computer does.

My MB is a straight 5, with turbo. The turbo doesn't add much to the equation. Tuning is via wrenches I bent with heat in a crack in the driveway. It doesn't know what a code is unless it is a reference to German wartime spies passing messages. If there was any plastic on it, the plastic would be consumed as fuel... Without a misfire. If it had a misfire it wouldn't tell you. I'm looking forward to its first rebuild in 300,000 or so miles, when it is 50 years old.

 

I think, unfortunately, the disparity in quality might have to do with the respective financial foundations of LR vs MBZ...

I'm pretty sure the Benz's are made of melted down Panzer tank parts by skilled and uber-****-retentive germans, while LR was limping along with 3rd world castings and the bittersweet memories of a dying global empire...

However, waxing nostalgic isn't curing my P0307.

A TD5 conversion would. But that's for another thread.

 

You can do a $30 head gasket test to rule that in or out. http://www.summitracing.com/parts/li...FWoS7AodA0wApw

 

"Low compression and slipped sleeves or a cracked block on a cylinder can cause misfires."
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In my experience, low compression does not, generally, cause misfire, nor does slipped sleeves, but what often does cause misfires, especially ones that many guys cannot diagnose----after checking items detailed above, sometimes repeatedly, they give up---is one or more minute cracks in aluminum wall behind one or more liners, due to that aluminum wall being, comparatively, quite thin. Most of the time, the cracking is directly caused from overheating of engine, and indirectly to some degree, from the stretch head bolts putting serious stress on specific area of block, or very close to it, (almost always directly across from base of head bolt, where cracking occurs most of the time. Such cracking is direct cause, most of the time, to the liners coming loose, "slipped liners," but the block cracking can and does happen often, with the liners not coming loose, at least for a reasonably long period of time anyway. The crack in aluminum wall allows coolant, coolant jacket is short distance from the thin aluminum wall, into the interior surface of liner(s), moves upward (sometimes downward into oil pan) and into one or more cylinders, which directly spark plug from firing, thus misfiring. This happens a lot more often than most people realize, with the Rover engine, and more often than most people want to admit.

 

I have another possible cause to add, although certainly way down the list.


I'm the 4th owner of my D2, with it starting life as a leased vehicle, then being sold as a certified used vehicle to the 2nd owner, then being sold to another owner, then to me. The 2nd owner got the shortblock replaced under warranty by LR. I was able to figure out who he was and I spoke with him to confirm the replacement before I bought the truck. He actually worked at a dealership and told me they were chasing an intermittent misfire without success when they finally bit the bullet and pulled the heads. The engine had about 68k on it at that point. They found that some of the cylinders were out-of-round and that the pistons were able to rock in the bore causing the misfires. After much bitching and threats, LR installed a new shortblock with round cylinders.


I did not experience the condition myself but I can say that 50,000 miles later the engine is misfire free.