Hello, welcome to Bamford Rose, and another question of the week. This week’s question of the week is a continuation of the subject of DB9 and misfire and a potential of primary catalyst failure as a result of the misfire. And specifically, we’re going to talk about the misfire monitor, because avoiding misfire means that you avoid a primary catalyst failure.

We talked about misfire rates, misfire type A, misfire type B in question of the week number 73, which we’ll pop a link up to here. So, it’s worthwhile watching that video and then coming back to this video, and to learn more about misfire.

Before we get into that, it’s worth talking about this DB9 that we’re in now. This is an early 2004 DB9. It’s got nearly 60,000 miles on the clock, but this car is extremely well cared for. We’ll talk a lot about some early low-priced DB9s being ones to avoid because they’ve probably been harboring a lot of problems. But you can sniff those cars out as soon as you walk up to them, you realize the pink condition is not as good as others. And when you open the door, look at the interior, it’s certainly well past its newness, and it’s a bit scraggy. And those are just early indicators that the car is a bit of a ropey one, and probably lurking underneath the car, what you can’t see is an even worse horror story.

There are plenty of those cars around and they trade at low mid-20s. So, if you were after an early DB9, a car like this one is one to seek out. Its high miles than the normal low miles DB9. You know, the Aston community considers anything above 50 high mileage. I don’t agree with that, really, because these cars, if they’re well serviced, can have the miles piled onto them and they will be good, reliable cars if maintained and serviced well.

So, an early DB9, this car is. High mileage, this car is. But this is not a car you would treat as caution, because the owner of this car has meticulously looked after this. Whether it’s been mechanical repairs, paintwork repairs, whatever this car wants, it gets. And as a result, it is in tip-top condition. It hasn’t got the DB9 dreaded tick, and at 60,000 miles, it’s probably unlikely to develop it. The meticulous repair and maintenance means the wishbone arms, bushes, radiator, air con condenser, door modules, all the normal sorts of things have already been done. And it’s these well-cared-for DB9s that will pretty much offer the next owner trouble-free motoring. And these are the ones to seek out.

Quite rightly so, it’s these sorts of well cared for DB9s that should command a much higher price in the marketplace, compared to a bit of a scraggier one. Side by side, this well-prepared car versus the scraggier car, they’re going to look more or less the same. The scraggier car might have a sale price of low mid-20s. This car, it’s very difficult to price this car. In any Aston, it’s based on spec, condition, mileage, service history. But compared to the price of low 20s for the less-cared-for car, this one is well worth something like 35. You know, that price differential is going to be less than what you will end up spending or repairing the less-cared-for car.

It’s just that the buyer, often untrained, doesn’t realize that. Meaning that for sellers who are quite rightly after a premium, like this car for they’re well cared for car is a difficult sell for them. Because people just have the eye on the cheaper cars, but don’t really know the problems that they harbor. So, that’s just a quick tangent we’ve gone off on to say that there are some great early DB9s out there. They do take some hunting after, but they are well worth hunting for and they’re well worth the additional premium.

Okay, so on to misfire and catalyst failure. Just before we go into a little bit more detail about monitoring for misfire, I want to say now that the 2 videos that we’ve done with Steve over at Aston 1936, we’re going to be doing another video with Steve on exactly this subject. We’ll be looking at the misfire, causes of misfire, the catalyst failure, and the impact of catalyst failure, what that can… can turn into in much greater detail. So, please check back on our channel, and also Aston-936 channel for that video where we both talk about the misfire and catalyst failure on DB9.

So, typically, misfire is from a number of reasons, but it’s going to be coil-related misfire, spark plugs need changing, maybe there’s a little bit of extra oil being pulled across in a breather circuit, and any one of those things can upset combustion, leading to misfire, which is a partial burn of the combustion mixture, meaning that an element of hydrocarbons, an element of unburned fuel is going on to the face of the catalyst, and because the catalyst is hot, combusts on the face of the catalyst.

This is really important to avoid on DB9, because if we look at a picture of a standard DB9 exhaust manifold here, you can see that the yellow line on this particular exhaust primary pipe runner is extremely short, meaning that the face of the catalyst is very close to the exhaust port of the engine. Because of a very large inlet to exhaust cam overlap that the V12 engine has means that there’s a suck back of gas that’s in the primary pipe very close to the exhaust port exit. And this is done as an emissions reduction sort of helper.

The downside of that is that, if there was any debris present in that gas, of course, normally there should not be, but means the engine will suck back up, ingest that debris into the combustion chamber. And bits of that debris get behind the piston rings, scuff the piston rings and liner. That grinding pace drops into the sump, and then it gets distributed across all crank and cam journals. So, it does pretty colossal damage to the engine, which in its worst extreme is irreparable.

Here’s a pic of a failed catalyst. And as you can see, there’s going to be quite a bit of debris floating around. And being so close to the exhaust port outlet, and because of that high inlet to exhaust cam overlap, means that all that debris gets sucked back into the chamber.

One of the subjects I’ll be covering with Steve over Aston 1936 is the frequency of this type of failure. Obviously, it’s a concern. You know, you wouldn’t want to be purchasing a car that has this failure, because the repair bill is so high. And in ownership, you want to do everything you can to avoid this problem so you don’t get a high repair bill, and an unnecessary repair bill. The engine would have lasted much, much longer. It was just failed by debris ingested because the catalysts failed.

At any given time in our workshop, there is never a V12 engine car, not inside the workshop needing a repair from this failure. I think 5, 10 years ago, this problem didn’t really even exist. This is because the cars still had some newness about them. And its age and deterioration that allows misfire to creep in. And then once misfire creeps in on the V12, catalyst failure is pretty much inevitable, and also inevitable is the suck back of the debris.

But whilst there is never a time when we don’t have a car, in the workshop needing this repair, and linked back to that question of how frequent this occurs, this never happens to one of our customers. This is because you can detect this problem with very careful analysis of the misfire monitor at each annual service. And it’s going to be bad luck that within 1-year service window, if you got the all clear at service, it’s going to be bad luck than to have a misfire creep in during that 12-month period. Because if everything is diagnosed as being perfectly healthy at a point in time, it’s going to take longer than 1 year, typically 3 to 5000 miles for deterioration to creep in to cause misfire, to cause the cat failure.

But saying that, a misfire can occur at any time. And as a driver, if you’re aware of the conditions which misfire can occur at so that you sort of monitor it yourself, then through the seat of the pants, you can feel that the engine is misfiring and seek a repair pretty quick before it does any damage.

The other way is if a fault code pops up on the dash, whether it’s an individual cylinder that’s misfiring, or it’s a general engine misfire. If that’s present, the fault code system will alert you to that fact. So, another tool to use is not ignoring any check emissions, check engine lights when they happen. Always plug in, always read the code. If you ever see a P300, up to P0312, these are all misfire codes. And you really need to get that checked out. If you plug in and it’s a lambda sensor fault, then, you know, they can be ignored and reset with robustness, because they’re often inconsequential.

So, it really is care and attention at service, which is the most important thing to avoid a misfire occurring and avoid a catalyst failure. And in terms of frequency, like I said earlier, it’s never one of our customers. So, this will always be a new customer to us. And it’s because this level of care of misfire monitoring has not been done as part of a service regime.

Now, it doesn’t matter whether it’s a franchise dealer, or its independents that don’t actually have the proper diagnostic kit to perform the misfire monitor. Whether you’ve got the kit, whether you haven’t got the kit, the root cause is inadequate detective time point of service, not enough time spent with the laptop in the car looking at all the conditions, which misfire occurs at. Static idling in the workshop and a good 3 to 5-minute observation of how the engine is behaving on the misfire monitor, and then drive the car, typically, 4th gear 2000 RPM, up a slight gradient, slow application of the throttle. It’s that onset of a little bit of extra load that you could get shudder in the chassis if a misfire was going to occur.

So, in terms of frequency people getting apprehensive about this problem. Well, if the car has been meticulously serviced and there’s no misfire present, then you’re unlikely to experience a catalyst failure. This particular DB9 60,000 miles on the clock, you know, this is service to death. And I’d quite happily drive to the south of Europe in this car, and even though it’s got its primary catalyst present, I wouldn’t be worried about it failing.

So, this question asked us to go into a little bit more detail on the misfire type A and misfire type B measurements of misfire. So, we’ve got a video here of another car that has got a little bit of low-level misfire at idle. Now, when you plug in with your generic fault code reader, you could get 0s in misfire type A misfire type B, and convince yourself that you have no misfire so you don’t need to worry any further. But this video shows how, depending on when you plug in, depends on if the real time misfire type A misfire type B monitor is reset. So, there can be misfires present, but you might have plugged your fault code checker in at a period in time where those counters reset to 0.

So, you can see on this graph that there are a few low-level misfires creeping in on a number of cylinders. And if we look at cylinder number 4 here, we can see that it’s ticking over and it has triggered a number of misfire type A and type B counts. And now. if we just sit and watch this misfire monitor run, over time, we can see the misfire type A count reduced back to 0, and over a greater time, we can see the misfire type B count reduced to 0.

So, if you happen to plug your misfire monitor in at the point where type A and type B misfire had the most amount of counts in, you would be fortunate enough to be alerted to the fact that the engine is misfiring a little. But if you plugged in at this point on the video, now the red bar graph indicates the history, and we can see this on our AMDS diagnostic tool. But on your generic fault code checker, you wouldn’t be able to see that history, and you’ll plug in and see 0s on the misfire type a misfire type B counts.

So, the importance of this, you know, at a basic level as a driver, you’re just going to be in tune with the engine, and know when to… or how to feel misfire. And we’ll drive this car in second and just reiterate the points that we’ve raised in a previous video to help you do that.

The next level up, you’ll be relying on the dashboard’s fault code light triggering, because the system has detected a misfire. On the next level up from that, you’ll be plugging in your fault code checker to interrogate real-time misfire type A and misfire type B counts. And the owner the next level up from that will actually be driving the car in certain circumstances, just to try and promote a misfire if it was going to occur, and see how those real-time misfire type A misfire type B count has count up. Or you could just take the approach where you don’t have to concern yourself with anything of that nature, drive and enjoy the car, and whoever you gave the keys to service the car, you just know, they’ve done all that work for you at point of service.

So, first off, we’ll check this car at idle. Now, it’s a big 6-liter V12 engine. And although it does run incredibly smoothly, when you’re sat in the cabin, you do get some noise, vibration, harshness feelings on the floor pan where your feet are in the seat if your arms are resting on the center console, you know that the engine is taking over. And by that, I mean that if you were deaf, you couldn’t hear the engine at all, just by sitting in the car, the vibrations that you are picking up from your feet, your arms, your hands would tell you that the engine is running.

So, what you need to do is understand the base level of those vibrations. And every now and again, just check that they are consistent, it’s always the same. So, it’s… I’m sitting in the car now. On the floor pan, I can basically feel the engine ticking over. You can feel some vibration on the floor pan. And what I do is open the door and then just hold the glass, because now I can feel a vibration through the glass. But on a car that’s misfiring, you can almost feel the glass moving, because the vibration has increased that much. Also, with the door open, if it had a misfire of any significant amount, you’re going to hear a little bit of torque tube chatter. And that rattle will be obvious it’s coming from underneath the car. So, getting yourself in tune with a normal level of vibration. And then like this car, listening, though it’s not exhibiting any torque tube rattles, these are 2 really quick and easy ways to detect whether a car is misfiring or not. And you don’t need any kit to do that.

So, now when we’re on the move, and we want to detect for misfire, we’ve got it in 5th gear doing about 40 miles an hour. And we’re just at about 15, 1600 rpm. And this is about the lowest vehicle speed in which you could hold this gear without it down changing. And now, we’re on a slight incline, and we just want to slowly increase the throttle. We don’t really want to pick up any engine speed, and we’re using that incline for gravity to sort of hold us back, meaning that we can just slowly increase the load, increase the load, and the engine speed is as low as you can maintain. And if the engine was going to misfire, it’s at this point that it’s going to do it, and you’re really going to feel that as a shuddering in the chassis. It’s going to be absolutely obvious if your engine is misfiring.

I mean, we don’t want to be driving these cars with apprehension all the time. But just like the pilot has a checklist to go through, and every single flight that you go on, you run through that checklist, then if you can build that checklist into your subconscious, and you’re almost doing it each journey without thinking about it, then every time you use the car, you really are protecting yourself from any sort of failure that could happen that, if you could prevent it would have prevented an extreme spend on a repair bill.

This particular DB9 is an absolute joy to drive, and I can drive it around all day and it would never misfire. If you did ever encounter misfire on your DB9, you don’t want to be driving it at all. The first hint of a misfire, phone up a breakdown company. Get it towed to a garage or get it looked at immediately without driving it much further. Because driving it with misfire is causing unburned fuel to go on the face of the catalyst, which is risking it breaking up with… which is risking it being ingested.

If you have encountered a misfire, part of the repair procedure is not just correcting the spark plug or coil or root cause in the misfire, it should be taken each of the lambda sensors out of the exhaust manifold, popping a camera down and checking that the face of the catalyst is in one piece and it hasn’t broken up.

If it has, not all is lost. We’ve recovered plenty of these cars, these types of failures. You can take the inlet manifolds off, clean them out, be totally sure that there’s no countless debris in there. Either perform a primary catalyst decap, or renew the catalyst manifold if the car needed to be kept to the standard, flush the oil. And had there been misfire, and had there been a small amount of ingestion, and if the miles were really, really low, then you’ll save that engine.

I know this because we’ve saved a couple of engines in this way. And I also know this because, at an establishment that you would have thought this wouldn’t have happened, we’ve had an engine come to us obviously in a car that’s extremely poorly, hardly wants to run, making some very nasty sounds. And whilst all 4 catalysts were present, there was catalyst debris in the inlet manifold. Because it had a misfire, it failed its catalyst, the intellect didn’t know whether to search further or what to search for. They repaired the problem that was wrong. They didn’t check if there was any catalyst debris in the inlet manifold. If they had done that, it’d probably saved the engine. They didn’t. The engine was run with… with the previous failed cat debris still in the inlet manifold. And that prolonged running completely failed the engine.

More often than not, these cars, especially as they’re getting older now and they’re out of the franchise network, they’re even out of the reputable independent network, are being worked on by people that shouldn’t really be working on the cars. They introduce problems, and then the cars can often get a bad rep because of some problems that’s been introduced by people and nothing to do with the car.

So, this car has finished its annual service with us. And after absolutely no hint of a misfire, quite sure that this car will go another year misfire free, in fact, any problem free because it’s been serviced by Bamford Rose. Have you found that insight into DB9 misfiring catalyst failure informative? Check out our future discussions on this with Steve over at Aston 1936. And we’ll see you in the next question of the week.