Wednesday, January 9, 2013

My Toyota RunX has a ‘check engine’ light on throughout

By BARAZA JM

Dear sir,
I own a Toyota Corolla RunX, 2001 model. Recently, the ‘Check Engine’ light came on as the engine was idling. Since then it has remained on whenever the engine is running.

Sometimes it goes off, but for a very short time. At first I thought it was the faulty battery I had which had problems cranking the engine, but after I replaced it, the problem persisted.

The car runs well, there are no funny noises from the engine, even at highway speeds. I haven’t taken the car to a mechanic (I’m low on cash right now), but I’m still bothered. Is there any cause for alarm?

Kenneth.

The best way to know what that ‘Check Engine’ light is all about is to do a diagnosis. However, these here are common causes of the light coming on out of the blue:

1. Faulty Oxygen Sensor: the device is not transmitting accurate information to the ECU and this is sometimes accompanied by a reduction in fuel economy. Cars have two to four of these sensors: the OBD code will identify the culprit for you. The cause is this: over time, the sensor gets covered in oil/soot and thus does not determine the quality of oxygen in the exhaust properly.

2. My research leads me to a very strange cause: a loose or cracked fuel filler cap. Apparently leakage of fuel vapour from the tank can very easily confuse the entire fuel system. This is also accompanied by worse fuel economy. Check the filler cap for cracks, or remove it and tighten it again, then drive a bit to see if the light will go off.

3. Faulty Catalytic Convertor: Failure of this device can be caused by 1 above (a faulty oxygen sensor makes the car run rich and this fouls up the plugs and the cat. Fouled plugs can be caused by a faulty oxygen sensor too. As you can see, these problems can sometimes be interconnected in a veritable web of complexity)

4. Faulty MAF Sensor: This is NOT the oxygen sensor as some are wont to believe. The oxygen sensor senses the amount of unreacted oxygen in the exhaust and adjusts the timing accordingly to optimise economy and reduce emissions. The mass air flow sensor senses the amount of air going INTO the engine and instructs the ECU to meter out the fuel accordingly via the injectors.

MAF sensors tend to fail because of a badly installed or rarely-replaced air cleaner element. A once-annual replacement of the air cleaner is just about enough to keep the sensor from failing.

5. Weak Electrical Connections: Plugs and wires in particular. This is usually accompanied by the vehicle jerking while in motion. Since you have not mentioned this, we can leave that at that. Only Part 3 would cause you to worry because cats are expensive to replace and require specialised skill to install.

Hi, I hope you enjoyed your trip down south. I confess I did not take your advice to sell my Mitsubishi Chariot when it started giving me trouble. I had it repaired and, despite the cost of having to change several sensors, I still kept the car.

Call me names, but I had become accustomed to its comfort. Now, the mother of all problems has come up; the gear is stuck at Three. I have had several diagnosis from different mechanics until my head is now spinning, but none of them has been able to solve the problem.

I have sworn the moment the problem is solved I SHALL SELL it. What do you think could be the problem? This time I promise to heed your advice.

Margaret (@MachariaWanjiru)

To reduce guesswork, obtain a code from the TCM (Transmission Control Module). This will give you a code from which you will know exactly what the problem is.

Usually this 3rd-Gear drive is the fail-safe, limp-home mode, which is usually triggered whenever the TCM receives an electronically generated error code. In case you cannot communicate with the TCM, then therein lies your problem: the TCM itself is cooked.

The transmission may have to be opened. A coil pack may have failed and overheated from an electrical surge, melting the module. Mitsubishi, for some reason, thought it wise to place the two in close proximity to each other. If this is the case you are facing some major (and expensive) repairs. I can bet the mechs will tell you: “Nunua gearbox ingine, Mummy!”

Hello Baraza,

Just to let you know, your column is remarkable! Here is my dilemma. I am looking for a seven- or eight-seater vehicle for airport transport business and car hire services, mostly around Western and Nyanza (as you know, Kisumu is now an international airport).

Comfort, reliability, availability of spare parts and a bit off-roading are important. I have in mind these cars: Toyota Estima 4WD 2.4cc, Toyota Isis 1800cc 4WD, Toyota Wish 1800cc 4WD, Toyota Sienta 1500cc 4WD.

I am aware they are all Toyotas, but you will have to forgive me because I am new in this. Any other suggestions will be really appreciated.

In an unrelated matter, there is this car I wanted to buy from a friend, a Skoda Octavia station wagon, 1.9 diesel TDi, 2006 manual gearbox model, for my personal use.

How would you size up this car in terms of reliability, performance, spare parts availability and fuel consumption. It is going for Sh650,000.

Thank you in advance.

Buy the Previa, also known as Estima. None of these cars will go off-road properly (what international airports are these you visit that require one to off-road a bit to get there?), but the Previa is the best in all the cars you mention.

You may have to compromise on economy (2400cc compared to sub 2.0 litre for the rest, and the bigger body); but not so you’d notice. And, believe me, that Estima is worth it.

It is roomier, more comfortable by far and better equipped. The Isis may have powered sliding doors as a boasting point (these doors fascinated me so much I took the car for a spin in the dead of night to find out what else was good about it) but that is just about it. It won’t do anything that the Previa will not. Thew same applies to the rest of the pack.

About the Skoda: damn fine car that is. Reliability is Germanic (good), as is performance, even in the diesel iteration you mention. It can outrun a Mk IV Golf GTI over the quarter mile, which is saying a lot.

Spares are also Germanic (a touch pricey) but CMC should have them. If not, try the Internet. Economy is superb. Just watch out for DPF failure due to our twig-ridden and waterlogged diesel, and there is the fear that high-altitude use causes the turbos to spin too fast and fail within a year.

Care should be taken. Invest in a turbo timer to be safe, use only high quality oil and, unless you are at the coast, keep the revs low. Avoid the temptation to drag-race a Golf GTI between red robots.

Hi Baraza,

I am a regular reader of your Car Clinic articles and I must stay I appreciate your work. Good job. I’m planning to buy a car but I can’t seem to make a choice between the Audi A4 (2005) and the Mercedes Benz C180/200 Kompressor (2005).

I am a Second Year university student and I want a car, between the two, that I can service well and move up and about with. Also, of the two, which one has a quick resale value?
Thank you.

Mwaura.

As a Second Year student, my choice of transport was to either walk or take a bus. Clearly you are facing a dilemma a lot different from that which I faced. Anyway...

Spare Parts and Maintenance: If this is a worry for you, then maybe you should be looking eastwards (read Pacific Rim/China/Japan) for a vehicle, not Germany; but here is your answer anyway.

Audi has no franchise at the moment; at least none that I know of, so getting spares may be a hit-and-miss affair. Also, these are not cars you want to take to the seedier avenues in lower Nairobi, or any other town, so getting someone to do a proper job of maintaining that A4 will not be easy.

You may have to queue up at Arrow Motors and wait your turn. Mercedes, on the other hand, receives good support from DT Dobie, so it wins this.

Fuel consumption: Again, if this is a worry, then maybe you should be making Second Year decisions like mine. Both cars will not hurt your pocket fuel-wise though: provided you don’t drive in a way that will fascinate your impressionable lady classmates.

Expect town-bound economy of about 7-9KPL and highway figures up to 16KPL. This also applies to the supercharged Mercedes. Keep those classmates away from your car though: extra weight is an enemy of good economy.

Resale: The Benz will fetch customers faster than the Audi. Kenyans fear Audis, except for the Q7, which for some reason (I don’t know this reason) they seem to love and worship. On the other hand, we also love Mercs and we are buying them in large numbers, especially the C and E Classes.

Hello Baraza,

I have four questions for you:

1.What determines the engine capacity of a given vehicle?

2.How is the engine capacity related to engine rating?

3.My car is a 1300cc Nissan B12. What is the typical fuel consumption rate of such vehicles?

4.What is the most economical speed one should drive at to ensure the car does not exceed the designed fuel consumption rate under ideal conditions?

Mbogo Munyau,

Embu.

1. The volume of one cylinder, which is got by the base area of the cylinder (pi multiplied by the square of the bore multiplied by 0.25) multiplied by the stroke of the cylinder.

The bore is the diameter of the cylinder and the stroke is the height of the cylinder. The figure you get from this calculation is then multiplied by the number of cylinders in the engine block (possible configurations are 1, 2, 3, 4, 5, 6, 8, 12 and 16).

The final figure is the engine capacity you are talking about, usually expressed in litres (L), cubic centimeters (cc) or cubic inches (ci, commonly used in the US when quoting the capacities of classic muscle cars/trucks).

2. By engine rating I assume you mean power rating. The general rule is: the larger the engine capacity, the higher the power output, but this applies up to a point. Other factors play an equally big role in getting the power of an engine: forced induction, material used to forge moving parts, valve timing/camshaft profiles, torque development of the engine, and how high (in terms of rpm) the engine can carry that torque.

3. There is what the rest of the world achieves when driving such cars, and then there is what I can achieve (if I may say so myself) when I go “economical”. Expect 10 or 12KPL in town conditions (this is greatly dependent on how bad traffic conditions are.

It could be as low as 5KPL in a particularly tight gridlock) and as high as 20KPL on the open road. I have once achieved 25KPL in a 1300cc EP82 Starlet without trying really hard. Typical returns should be about 17 or 18 KPL for “normal” highway driving.

4. Keep the revs at about 1,800rpm or slightly less in top gear. This avoids engine strain due to low-rev driving, and the revs are still low enough for the car to sip.

Whatever speed this occurs at is the optimum driving speed for economy. It is possible to get even better economy than this, but from there you will be straying into hypermiling territory, which is highly risky, a bit technical and sometimes dangerous.

Hi Baraza,

Greetings from southern Tanzania! Great work you are doing with straight-up answers to our motoring queries. My organisation wants to buy several double-cabs for a project this year.

The options are Toyota Hilux, Nissan Hardbody, Ford Ranger and the all-new VW Amarok. Kindly share your thoughts on power, off-road capabilities, comfort, drive feel and overall ranking.

Cheers,

Sam

Power: The Amarok Bi-Turbo and the Ford Ranger lead the pack at 176 hp and 197 hp (2012 model, 3.2 TDCi) respectively. The rest are left floundering at the back. The Ranger wins out on torque also: 470Nm compared to the VW’s 400Nm.

Off-road ability: All these cars will go off-road convincingly. They are all fitted with proper off-road kit in their 4X4 iterations, and they have ground clearance to boot. Seeing how none of them use fancy viscous couplings/torque vectoring technology with that 4WD, this makes them all equal players in the field.

Getting far from the beaten track in one will depend on how skilled the driver is.
Comfort: Interesting state of affairs here.

The Amarok I tested was the base model 4X2 diesel turbo, and it was the most uncomfortable double-cab I have ever driven, owing to a ride quality that was both bouncy AND hard.

A South African colleague, however, has driven the Bi-Turbo, and he, on the other hand, tells me it is the most comfortable in the pack of double-cabs he has tried. This may be true, as you will see in just a moment. The Hilux is next in line from the bottom, then the Hardbody is in third place.

Feel: Hard to tell. The base model Amarok is really not that good, but again, the Bi-Turbo comes with an options list like that of a German saloon: featuring things like wood and leather.

The Hilux has a bright grey interior that is not at all endearing while the Hardbody’s is a bit better and darker shade of grey. The Ford’s interior, judging from what I saw at the launch, could very easily be the best here (until I see that wood-and-leather Bi-Turbo, that is).

Drive: Both the base-model single-turbo Amarok and the Hilux suffer from tremendous turbo lag. While the Hilux stays breathless almost throughout, the Amarok will run off into the distance.

The Bi-Turbo should counteract this by having that extra turbo under the bonnet to reduce lag. The Hardbody is a bit so-so (definitely more involving than the Hilux) while the Ranger....

Overall Ranking: You might think this will go the Bi-Turbo way, but then you’d think wrong. You may have noticed that I don’t say much about the Ranger in Drive, Feel and Comfort; and there is a very good reason.

Even after promises were made, I am yet to drive the Ford Ranger. So I cannot rank it conclusively against the rest of the pack. Judging from what every other motoring journalist has said, however, the Ranger T6 is almost as good as good gets in the double-cab world. So it gets first place.

Then the Amarok Bi-Turbo comes second. The Hilux is stone dead last. Poor ride quality and the unresponsive, lag-plagued and underpowered engine are the car’s worst failings. A naff interior also doesn’t help matters. The Hardbody is much better. 

Having car trouble? Send your queries to dn2@ke.nationmedia.com for absolutely free expert advice.

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