Tim Shallcross

Email Tim with your questions

Hi Tim,

I have a Porsche 997 Carrera S, November 04, that I've owned from new. It has 47k miles with full Porsche centre history, and I use it more or less daily. It has been run almost exclusively on Shell V-Power and BP Ultimate fuels.

Buying the first of a new model generation has, with hindsight, been an error, and the car has been plagued with problems to the extent that I renew warranty and roadside assistance cover annually. I note the price of this increases every year too !

I have a long term problem with under-performance, where the engine feels as if it's struggling to breathe. When squeezing the throttle, sometimes the car will feel distinctly under-powered. Occasionally this will go the full way to a misfire, but, being intermittent this is often just added vibration and reduced performance sporadically during a journey. Most of my driving is motorway or A-road cruising where this is most apparent, as a low-rev lack of torque.

More often than not the computer does not record a fault. Extreme cases of roadside breakdown have clearly identified coil failure, and I've had them replaced at least 3 times now. I've also recently had a new air-mass sensor, as this is a common fault. One further clue, on bad days the car will start but with a notable petrol smell in the morning from the exhaust.

After the most recent (September) round of coil and air-mass replacements, no fault is logged on the computer which means the only remaining option is to open the engine. However, this is something for which I'll have to pay, as the warranty will not cover this until a warrantable fault is found. Therefore I leave myself open to 10-20 hours labour at £120 plus VAT an hour. The garage and I have an amiable relationship and I'm sure I could negotiate this down.

My alternative is just to keep driving it, and let the warranty pick-up the failures as and when they show. It's just annoying driving a car which doesn't drive right.

I would appreciate your thoughts.

Kind Regards

Robert Prince, UK

First, a bit of armchair diagnosis based on what you’ve described. The “added vibration” and sense of loss of power both suggest one cylinder or more misfiring, but if that was an ignition problem, unburnt fuel should be detected by the oxygen sensor which in turn should trigger an engine management warning light and a fault code in the computer. However, that doesn’t always seem to happen and the petrol smell in the morning might be another indicator of a misfire. Once the cat warms up, unburnt fuel smells like rotten eggs, but for the first few minutes after start up, the fuel passes straight through the cold cat and you will get a petrol smell. For some reason the ignition coils on these engines seem to last about as long as a tank of petrol, so it might well still be a coil problem. On the other hand, the smell could be an indication of overfuelling due to a duff coolant temperature sensor. Alternatively the evaporative emissions system can give a very strong petrol smell if the carbon canister valve is stuck open, which can also give a misfire... OK, I think we can conclude that accurate diagnosis from an armchair is not easy – rather like the diagnosis you get from the bloke in the pub who knows a bit about cars.

So, some more common sense and practical advice about what to do. This was Porsche’s first venture into water cooling after years of sticking with aircooled technology, and the early engines did get a bit of a reputation for cracking heads and cylinder liners – although the reputation seems worse than the facts. You mention a full Porsche service history, so I assume that means the garage is an Official Porsche Centre (OPC)? Do they acknowledge that there’s a fault and have they asked Porsche to send an engineer to investigate? Regarding “opening the engine”, that seems a bit extreme without some further preliminary investigation – otherwise, what are you looking for? A cooling system pressure check is pretty straightforward, even on a Porsche and it will give you a clue as to whether you have the dreaded cracked head. A compression test will give a further insight into other possible mechanical flaws. Measuring the temperature of each exhaust manifold can also give a great indication of which cylinder’s giving problems.

Porsche is an unusual manufacturer because the cars tend to be kept going for ever, so there are quite a few independent specialists in older cars who have a proper motor engineering background and in many cases they seem to have more expertise than the OPCs. Hartech up in Lancashire is probably one of the best; they have excellent and comprehensive buyers’ guides on their website, detailing common faults. (Be warned; when you’re reading them, you feel as if you’re being given a lecture by the headmaster after being caught smoking behind the bike sheds, but there’s lots of good information and once they’ve told you off for not buying one of their cars they seem very helpful.) I would consider contacting them or a similar specialist before committing yourself to paying an indeterminate amount for proper diagnosis.

www.hartech.org/

Dear Sir,

I would value your opinion on the situation I find myself in - the weekend before last I purchased an Audi 80 estate, M reg, diesel from a dealer near my home in Enfield. I test drove the car the preceeding week and other than a bit of vibration from the steering wheel at 60 mph, it seemed a reasonable purchase. The car had an MOT till April 2010, and no advisories recorded on the previous one. The Audi service history was there along with plenty of other bills for consumables and parts replaced, all the MOTs going back etc. One would think that it would make a reasonable purchase, not immaculate but a decent-ish buy that would keep going for a year or so, or at least until the next MOT. The vendor had apparently carried out HPI and DVLA checks as advertised on his website.

However, I booked a service at my regular dealer who reported that the car in its present state would fail an MOT, on account of several suspension-related issues (sub-frame cracked), two tyres worn down to the steel and several other faults, which leave a repair bill of over £1000. I cannot afford this!

The dealer from which I bought it has agreed to take it back for a look and to conduct his own inspection - can you advise as best you can what my rights to recompense are with him. He seems a fairly agreeable sort of bloke. The car was not 'sold as seen', which I understand would leave me with nothing.

Many thanks,

David Malleson, Enfield, UK

Get your money back fast – you can still reject the car so do it now. Even if you paid a low price for the car, it should have been roadworthy if it came from a trader. No argument, just do it. Next time, if your budget’s limited, the cheapest form of vehicle inspection is an MOT – ignore how long the current MOT has to run, take the car you’re thinking of buying for a test at the place that’s just looked at the Audi. £50 or so will tell you everything important about it. Audis are not bad, but at this age any car will have faults and on an Audi they’re expensive. Go for less image and you’ll get a lot more car for your money.

Hi Tim,

I have recently come across two economy measures which Googling hasn’t resolved the question of their effectiveness.

1) Filling tyres with Nitrogen

2) The use of diesel additive COUNTdown from highspeed.co.uk.

Have you any opinion? Thanks,

John Valentine, UK

Additives are generally rubbish unless used under very controlled conditions – and even then you’re better off with BP Ultimate or V Power etc. That’s because the additive has to be added in very controlled quantities, otherwise you either don’t get any benefit because there’s too little or you waste money by putting too much in. By an advanced fuel and it’s already done for you. There’s much debate about whether you actually get any benefit, but the potential is certainly there if you avoid using it for extra performance. Try some careful measurement of your mpg with ordinary fuel and an adveanced fuel to see if it’s worth the extra cost.

Nitrogen in the tyres is a complete waste of time. Some racing teams use it because it’s easy (comes in compressed cylinders so you don’t need compressors etc) and inert, (so it won’t feed a pit lane fire the way compressed air might). There’s debate in various internet forums about other merits, but consider that (a) compressed nitrogen isn’t pure – it’s about 95% nitrogen, (b) unless you get all the air out of the tyre first, there will be a mix of air and impure nitrogen in the tyre anyway, taking the % of nitrogen down to, say, 90% if you’re very lucky, and (c) good old air is about 80% nitrogen. So, the big deal about nitrogen inflation is...????

Forget gimmicks, check your tyre pressures regularly and drive sensibly. That’s how you’ll get the best economy.

Hi Tim,

I would really appreciate some advice. I bought an audi A3 2002 model from a garage. When I first took it away (paid £3,200) it was fine, then a few days later I noticed that the sensor on the dash always stated the door was open even when shut, which caused the alarm to go off. And also I had a problem with the turbo losing power when reaching 70mph in top gear. The garage only gave me a month warranty and I took advantage and took it back. They fixed the sensor in the door and tightened tubes in regards to the power loss. Now all seemed well again until the warranty went out. Turbo loss again and instead of sensor saying door was open the whole dash flickers on and off. I then took the car to a garage I am familiar with and they run a diagnostic. Stating that the power loss was due to turbo "losing power". I had all the tubes tightened. Still after two days this still was happening. In regards to the flashing dash I was advised loose wires from the battery. They said they fixed this then two days later started again. I was advised I should go back to the garage that sold me the car even though the warranty has expired as the problems were reported before and not fixed properly. Just wondering where I stand with this and any advice would help as I am now pulling out my hair and wishing I never bought the thing.

Many thanks

Liam Jamieson, UK

It’s not clear whether this is the TDI or the 1.8T petrol (20Valve). If it’s the diesel, replace the boost sensing pipe from the turbo to the ECU – it’s a common cause of power loss above 3,000 rpm. The dashboard is a poor connection or a dry joint on a circuit board – it needs tracing properly and fixing permanently.

All that aside, I think you should try to reject the car if you’ve had it less than 6 months – it’s still possible after more than six months but more difficult. If you have documentation about the faults – receipts or letters from you to garage, keep them. If not, start now. For a purchase under £5,000 you should pursue a claim through the small claims court if the garage is being difficult.

Sir,

Are you aware of the alarming wear rate issue on Saab rear brakes?

Specifically that they wear out between service intervals even if you start with new components.

The front brakes appear fine (should last 40-50,000 miles).

I have personal experience of this on my MY08, and have checked with a half a dozen dealers all saying rear pads last 15-20,000 miles. On dealer said that in his area the average was 12,000 miles. Given the service interval is 18,000 miles, brake failure is almost guaranteed on any vehicle where the service interval is defined by mileage rather than the 12 month interval.

Obviously the rear pad material is inadequate, or the front-rear bias is overloading the rear brakes.

I am an automotive development engineer with 30 years experience, and as such know that this is a serious problem.

I have various emails from Saab (including some from the MD of Saab UK) denying the issue.

I have also checked the Saab forums on the net and customers have been complaining as far back as 2007 so this is not a new problem.

Perhaps this is something that would be of interest.

Regards,

Mark Berry, UK

You don’t mention the model, but in general I wouldn’t say that Saabs are any worse than many other current cars. It seems that rear pads do seem to wear out more rapidly for some drivers. There is a brake wear indicator, so even if the pads wear down between services the dashboard warning light should alert you to the fact that they need changing, and this will illuminate well before they become dangerously worn. There are a couple of possible reasons for the higher rate of pad wear. First, manufacturers are keen to reduce weight where they can to improve economy. Modern pad material, disc cooling technology and servo assistance all mean that the size and weight of the rear brakes can be reduced without in any way reducing brake efficiency (as long as you don’t include service life in efficiency!). This is important because there isn’t one single bit of a car you can lose significant amounts of weight from – it has to be bits shaved off here and there. However, a smaller brake working harder will wear out the pads – and discs – more rapidly. Second, electronics have taken over the brake force distribution between front and rear brakes, and as always it does it more accurately than the old mechanical/hydraulic valve. The point of brake force distribution is to make certain the front wheels will always lock up before the rear ones, so that you don’t spin in a skid. The bias on older systems was set to err on the side of safety, so the back axle would tend to be under-braked in relation to the load. You might lose a little bit in total braking efficiency, but the car stays in a straight line. The front/rear braking balance today is incorporated into ABS system and there’s more effort going to the back brakes for the same load – you can safely go to the maximum rear brake effort and let the ABS take care of any danger of the wheels locking. (That’s also why you should not drive a modern car with the ABS light on, other than carefully to a workshop. I still hear people being advised that the brakes will work perfectly well, you just don’t have the anti-lock capability. Not true; you also lose the front/rear balancing which makes emergency braking a potential spin. If the ABS light comes on, get the brakes fixed straight away.) This extra braking effort will exacerbate the wear.

Another point to bear in mind is that 18,000 miles between services is a long way; it’s three quarters of the way round the world. Maybe we need to start thinking about car maintenance in a different way. For more on this, click here...

Hi Tim,

I have a 4 year old VW Golf, 50 Plate, that I have owned since it was 6 months old.

The car has always suffered from misting/steaming up of windows.

In general in the summer months it doesn’t happen but on some days when there has been rain or damp conditions followed by sunshine or warm weather I have noticed that operating the fan during the first few minutes of the car running causes the windows to steam up.

During the winter I have to be careful not to use the heater until the car has at least partially warmed up.

I have taken the car into the dealer a number of times over the last 3 years and they have never found a problem despite my insistence that one exists.

I suspect a problem with the Air Conditioning/ Fan unit. I have tried looking on motoring forums etc but have not found any explanation to get me nearer the cause.

Brrr,

Neil, West Midlands, UK

First make sure that you really do have a problem; it’s not that unusual for the windows to mist up if you put the fan on before the engine starts to warm up – but this should not last more than a couple of minutes. If your local dealer is friendly, go there first thing on a damp morning (there should be no shortage of them just now). Start one of the cars on the forecourt and see if it does the same as yours. If so, it’s normal. If not, at least you can show the dealer that you’re nor imagining it. However, assuming there is something abnormal about your car, it’s caused by water inside the car or in the heater system. For some general advice on keeping your car dry, comfortable and fog free until next Spring, click here...

I have a 15 year old saab convertible which has a pale green lichen-type fungus growing on the roof in places. They are mostly about half an inch in diameter and nothing I have tried so far has been successful in removing them. I've tried various soft top cleaners, scrubbing with a stiff brush, even using a very sharp knife to try and pick it off, but I don't want to damage the fabric. I even sprayed the roof with round-up in an attempt to kill them. Do you know of any products or cleaning methods that will bet rid of them? I appreciate that you're not a microbiologist, but if it helps, I'm sure that they are probably the result of parking for many years in a station car park which was overhung by sycamores.

Justin Charlton-Jones, Winslow, UK

It sounds as if the roof may be beyond redemption. It should have a good waterproofing treatment, which must have broken down to allow things to germinate in the fabric. Roundup was a good thought, but there’s not much leaf area to absorb the stuff. A good moss/lichen/fungus killer might be better, but these tend to be a bit bleachy, so you may well mark the roof. There are firms who specialise in renovating convertible hoods – try: www.clean-image.co.uk/valeting_convertible.htm

Dear Sir,

Mercedes Benz in higher Class cars as the Class CL and S has introduced the Active Body Control (ABC) suspension system against rolling in curves.

In other also fast and expensive cars as the CLS 500 or the CLS 63 AMG has introduced the Airmatic DC suspension for similar reasons.

The question is why there is not any ABC in the CLS Class cars? Is for the CLS the Airmatic DC sufficient against rolling in curves?

Thank you

Best Regards

Andrew, Athens, Greece

Both do pretty much the same and if it’s good enough for the Mercedes engineers, it’s good enough for me. If you’re in any doubt, you could always try driving through bends at a sensible speed – you know, the sort of speed where you can stop if something turns out to be in the road just around the bend...

Hi, I have a Renault Master van with a semi-automatic gearbox or rather an automated manual gearbox.Is it electricly or hydraulically opperate? It also has "snow control" and "load control" switches what do these do ?

Thank you

Graham Thomson, Edinburgh

Both. It’s an ordinary manual gearbox with some electric and electro hydraulic servo motors to do the gearchange and operate the clutch and a computer to control it all. The advantage is that you get all the efficiency on a manual gearbox – no losses through a torque converter, but with the relaxed left foot in traffic you get from an auto. The drawback is that the gearchange can feel very jerky compared to a conventional auto.

Snow mode limits wheel spin when pulling away on icy roads. Load mode adapts the shifts for a heavily laden van – it reduces clutch slip and alters the gear change points to take into account the extra weight

Hello,

I have an Alfa 156 JTS veloce Ti, 55 plate. Sadly, I now need a car which can accommodate my dog - an Irish Setter! So I need a hatchback or estate, which can also carry my 15 month old and 7 year old girl, as well as assorted friends. I need a car in which the passenger airbag can switch off to allow the transport of kids in the front when necessary. I also want something that is reasonably powerful, and a bit stylish (tough, I know)

I have a budget of around £6000 including my car, which has done around 50,000 miles. I though I had cracked it with an Impreza hatchback, but lo & behold, airbag permanent. Can you help?

Mrs M, UK

A bit stylish? Impreza? You’ve had the style and good taste to buy an Alfa; you can’t possibly like an Impreza. Buy another car to take the dog out. Or get a sports car and refuse to take the kids anywhere – we’re supposed to be encouraging buses, walking and cycling and it’s their planet we’re ruining, let them make some effort to save it...

OK, I’ll be sensible. What’s wrong with the Alfa Sportwagen? A brilliant car, great engines and stylish with it. The airbag only needs to be switched off with a rear facing child seat in the front. A 15 month old should be big enough for a proper child seat by now, so leave it on, use an appropriate child seat and move the car seat right back. Then get the Alfa Sportwagen. And teach the dog to wipe its feet!