What is the problem with modern diesel engines? - Daily Nation

What is the problem with modern diesel engines?

Tuesday March 26 2013

By BARAZA JM

Hi Baraza,I recently bought a second-hand VW Touareg with a five-cylinder TDI engine from the UK. While I love the car (after replacing the shocks), I fear I may have not done my pre-purchase selection well enough as I have been informed that local agents refused to stock diesel Touaregs due to a potential mismatch between our local diesel quality and the VW common-rail engine.

I have also been informed that similar issues have been identified with the new Land Rover diesels, which are also common-rail. Is there an identified problem with this type of engine? If so, what is it and what can be done to avoid problems?

Many thanks in advance, Moose

Moose, I find this interesting because I know CMC sold diesel as well as petrol Touaregs, MK I version (or did they?) What I know for sure is that they sell diesel Land Rovers (and Range Rovers); in fact, last year they were proud to show me the new 2.2 turbodiesel in the Defender, bringing smoothness and economy to a car that knew none of these things.

The diesel engines that I am fully aware of failing courtesy of our diesel are Hyundais: a recent visit to the premises revealed that tests done resulted in engine failures after a mere 50,000km —  an unacceptable premise. As such, the Hyundai agent here will NOT sell diesel engines.

According to the Internet, our diesel contains 50ppm (parts per million) sulphur content, same as South Africa and Morocco. Sulphur is a naturally occurring component of the crude oil from which diesel is derived.

Fuel-bound sulphur is also the enemy of the environment. During combustion, this sulphur creates soot and particles, among other things, and this is where a device called the DPF comes into the picture.

DPF in full is diesel particulate filter. When the soot and particles (particulate matter) are formed after combustion, in the interests of emissions control, the DPF traps them as they try to leave with the exhaust gases. Accumulation of these particles in the DPF results in a slow clogging process that increases the exhaust back pressure.

There is a sensor for this back pressure that informs the ECU to increase fuel delivery via the injectors so as to create a heat build-up just ahead of the DPF and thus burn off these particles. It is a circle of life, so to speak, and it happens so fast you will not notice it in a process called “regeneration”.

All new age diesel engines (of late CRD — common rail diesel — has been the fad, rather than DI — direct injection) are required to have this device to control emissions.

The push for low-sulphur diesel also caters for those old engines that have no DPF and are yet to be grounded. The Euro IV standard is 50ppm diesel. Euro V calls for 10ppm or less, enforced in 2009.

Naturally, every quick-thinking manufacturer would have started building Euro V-standard engines ahead of time so that by the time it comes into force, they will not be caught on the wrong side of the fence.

So what happens when you feed Euro IV-compliant fuel into a Euro V-specified engine? Soot build-up is going to exceed regeneration ability. The DPF will get clogged. A warning light will come on the dashboard. Fuel consumption will shoot up. Power will drop.

At the critical level of 75 per cent, the vehicle will stall (same point at which many more dashboard lights will come on). So you will have to bring the car in for regeneration or a DPF replacement. These things are not cheap: one costs Sh130,000 or more, depending on manufacturer.

With this happening on a regular basis, you can see why my Car Clinic and the income statuses of several garages will flourish. Replacing a DPF every three months will ring alarm bells with your bank manager and your spouse, who will both refuse to believe that the expenditure falls under “running costs” of a vehicle (are you driving a Veyron, for goodness sake?)

A trick that I have seen some people use is to remove the DPF altogether, but if you opt for this, you had also better have knowledge on how to map a vehicle’s ECU because the car will not fire up when the DPF is absent. Reprogramming allows the ECU to “overlook” the missing DPF, or the new programme simply omits the DPF code, so as far as the ECU is concerned, the engine was built without a DPF.

One way to avoid problems is to avoid town-based stop-start driving. This does not create enough heat for passive regeneration (where the heat of the exhaust is used to heat up the DPF to burn off the soot), so instead active regeneration is applied, which is what I described (the DPF sensor tells the ECU to burn more fuel).

It is self-defeating in a way that burning more fuel to de-clog the DPF results in more clogging. Also, regeneration as soon as the warning light comes on will save you replacement bills (but this will still happen often).

The third option is to remove the DPF. If you go for this, I know of one Amit Pandya, from AMS Chip Tuning & Performance Centre, who knows how to sucker ECUs into doing his will. (Note: This is illegal in countries where emissions are taken very seriously).

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Baraza, I like your informative columns. I bought a Toyota Fielder six months ago. Whenever I start the car it behaves alright but upon accelerating, the engine light flickers on and I always notice gear(s) above Number Three do not engage. This makes the rev counter stretch towards the right and by the time I hit 120kph the rev counter is beyond four.

When I drive for long distances the Check Engine light goes off, then the gears engage smoothly and the revs fall to between 2000rpm and 3000rpm, depending on the speed.

I have changed the engine oil and the ATF and also ensured that the right quantities are maintained, but the problem persists.

Diagnosis on two occasions has indicated revolution sensor failure. In the first instance, the mechanic said the entire gear box needed to be be changed but since I did not have the money I went to the second one, who suggested that I change the reported sensors, but the problem persists. I would like to know the following:

1: Must I change the entire gear box, as suggested by the first mechanic, or can the failing gear(s) be repaired?

2: How many gears does my car — a 1500cc Fielder, 2004 model — have. Are they four or five so that I can know how many after the third are failing?

3: Why does the engine light sometimes disappear and gear(s) engage normally? Could it be a wiring problem?

Thanks,

Very Disturbed.

Hello Mr Very Disturbed,

Here are the answers I could come up with for your quandary:

1: I do not think replacing the entire gearbox is necessary. Sensor failures are best cured by sensor replacements. Also, I find it unlikely that individual gears within the gearbox may be ruined. Yours sounds strictly like a sensor problem. Sensor replacement SHOULD cure the problem, although in your case I strongly suspect the sensor replacement may not have been done properly.

Then again, the problem could be in the wiring: there might be a loose connection somewhere, or a circuit board has been jarred free of its connections, hence the new sensor not making a difference. Electronic problems can be a real headache sometimes. If this is the case, then believe me; a new gearbox will not help either.

2. The OEM automatic gearbox in a 2004 Toyota Corolla Fielder 1.5 has four speeds.

3. Yes, as I mentioned in Point 1 above. Now, what you have to do is get a more enterprising mechanic who is not afraid to think outside the box. He will go through the entire electrical path until the problem is found: and more likely than not this will solve the problem.

Hopefully you will stop being Mr Very Disturbed and become Mr Very Relieved.

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Dear Baraza,I am very curious about the Toyota Vanguard. I have seen a few around and I would like to know the difference between it and the RAV4 because they look so similar. Thanks,Muya

Actually, you are right: it is the same car, it is just that one is slightly longer than the other.

Since the Generation 3 RAV4 came out in 2006, Toyota has been building the vehicle in two wheelbase configurations. The smaller cars went to Europe and Japan. The US and Australia got the lengthy version. Japan also got the longer vehicle, but to keep it apart (and away) from the RAV4, they called it the Vanguard.

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Hi Baraza,

Thanks for your informative column. I drive a VW Passat 2003 model (1800cc) imported from the UK. It has been a smooth ride since I imported it two years ago. However, lately, I have had issues with the transmission system. When the engine is cold, I have no problem engaging Drive. However, when in traffic and change from Neutral to Drive, I experience a severe jerk which started out slowly but is now quite noticeable.

Computerised diagnosis turned negative results, while my mechanic recommended that we top up on the ATF, which we did with the recommended type from CMC. Sadly the problem persists.
My mechanic now says we should replace the current ATF, but I am wary of this, considering the exorbitant cost.

Another mechanic reckons that my engine’s revs are rather high and that this is what causes the jerking when the engine is fully warmed up. Any idea how to sort out this nagging problem? I love the car but I am worried that soon it might just stall in the middle of the road... at night!

Regards, Jeff.

When the mechanics say the revs are high at idle, how high are we talking about? What rpm? Quite a number of engines have a high idling engine speed when cold-started in a bid to warm up the engine quickly, though this high idle usually drops immediately the gear lever is slid into Drive.

However, that fast idle may be connected to the violent drive engagement. The first steps of diagnosis are usually:

1: Verify that the transmission fluid level is correct, which you say you did, but it could be too high and I suggest you also flush the system and put in all-new ATF, just to see if it works. It is not as expensive as having your car coming to a stop in a dangerous neighbourhood at night.

2: Verify that the valve body, throttle valve, and transmission shift linkage are adjusted properly. A slightly open throttle valve will cause the engine to rev up, and the drive engagement will create a shock, which you experience as that thump.

However, a more technical approach (when the above has failed) involves the replacement of the transmission valve body’s upper housing separator plate and a valve body check ball. It also involves erasing and reprogramming the Powertrain Control Module (PCM) with new software.

These are the steps:

1. Refer to the appropriate year information on Transmission and Transfer Case removal and installation instructions of the transmission valve body, check ball, upper housing separator plate, and pan gasket.

2. Replace the original rear servo check ball with a new plastic check ball.

3. Clean the new separator plate to remove any dirt or rust inhibitor prior to installation.

4. Instal the new transmission valve body upper housing separator plate.

5. Reassemble the transmission.

6. Instal a new transmission pan gasket.

7. Lower vehicle and instal transmission fluid.

8. Verify fluid level after warming up the transmission and cycling the shift lever several times.

9. Verify, and if required, adjust the transmission shift linkage and the transmission throttle valve cable per the appropriate service manual procedures.

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Hi Baraza,I am an avid reader of your column and must commend you for the good work. I own a Subaru Forester, year 2000 turbocharged model. She has been awesome, to say the least, but time has come for me to move on. I have been eyeing one of the following: Basic Outback, 2.5-litre engine (year 2006-7), Outback 3.0R (year 2006-7) and BMW 3-series (328i) saloon or estate (year 2006).

Given my relationship with the Forester, I am a sucker for power and stability. The upgrade should match this and also offer added comfort (Foresters have had the reputation of squeezed rear leg room). Slight off-roading (village terrain but not Rhino Charge) is also one of the requirements.

What would you advise me to go with, taking into consideration fuel consumption and maintenance? One more thing, any issues to look out for from UK imports?

Many thanks,

Mugambi.

The BMW will tick almost all the boxes until it comes to the village off-road part. Then it bows out. The 3.0R Outback will offer everything, but you will pay at the fuel dealer forecourt. The 2.5 Outback’s performance may not be at the same level as the 328 and the 3.0R, but then again, how fast do you want to go in a bus designed to ferry the children of the well-off to grade school in the morning, music classes in the afternoon, and out-of-town horse stables on the weekends? It will also not burn as much Premium Unleaded as the 3.0R.

I do not know how much power and stability the turbo Forester gave you (for all I know, it could have been an STi), but you have to make the choice here. The 328 is not even closely related to what you were experiencing. The decision lies between the Outback 2.5 (better economy than the 3.0R) and the 3.0R (runs like hell, but also burns fuel like hell).

Choose.

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Dear Baraza,

I currently drive a Kenyan muscle car, the Toyota DX 103. It has been a good car and has been to all the corners of this country, but lately it has developed the habit of leaking engine oil. My engine gurus are yet to crack the problem, despite advising me to start using Shell oil and checking the cooling fans.

What do you think could be the problem?

S N Mwangi.

What type of engine does that DX 103 have? Because I suspect you are using the term “muscle car”  very loosely here. Either loosely or with sarcasm, in which case I salute your literary skills.

What I do not salute is the problem-solving approach you and your “engine gurus” have. Either there is something you are not telling me or your “engine gurus” must deal with some other engines, not the internal combustion versions.

I do not see why, when your car has an oil leak appearing on the engine block, you check the cooling fans and replace the oil. What gives? You have not even said that you tried to find the leak; from your description it sounds like you were trying to solve a cooling problem and upgrading your brand of oil.

Check for a leak (obviously). These are the common causes on how one could find oil on an engine block as a result of a leak:

Bad or worn out gaskets (valve cover gaskets, oil pan gasket).

Oil plug (drain plug) not secured properly.

Oil plug worn or damaged.

Oil filter not attached correctly or missing gasket.

High oil pressure (a problem in itself).

Oil coolant line corroded or leaking

Rear seal.  This one is difficult and expensive. There is an oil seal at the rear of your engine near the transmission.  Typically it is difficult to see this one but you will know if you have a leak due to lots of blue smoke coming from the underside of the car at the rear of the engine. If you have this problem, bring it to a mechanic as the engine will have to be removed to replace the seal.

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Hi Baraza,

I am currently in Australia and will soon come back home after studies.
I really love Land Rover vehicles, and a friend in the UK has agreed to help buy one and ship it to Kenya for me. The Freelanders are a cheaper, but another friend tells me these cars are very problematic but does not give me the specific issue with the engines. TheFreelander V6i ES model has an engine capacity of 2,497cc, the Freelander Kalahari S/W 1,796cc, and the Freelander XEI S-Wagon 1,796cc.

I need a car that is fuel-efficient and can last for many years. Does a lower engine capacity mean better fuel efficiency? What is the difference between the Freelander diesel engine and the petrol one?

Thanks,

Alex.

Generally, yes, smaller engines burn less fuel... disregarding issues like forced induction and heavy bodies. The difference between the Freelander petrol and diesel engines is that, well, one uses petrol and the other diesel. Also, some diesel engines are limited to 2.0-litre capacities only while petrols have varying capacities and cylinder counts (from 1.8 to 3.2 and 4-6 cylinders).

However, as of January this year, the Freelander 2 now has TWO diesel engine options: 2.0 and 2.2, and the V6 petrol 3.2 has been done away with. Instead, you can get a turbo 2.0 petrol with only four cylinders.

Having car trouble? Send your questions to [email protected] for absolutely free expert advice.

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