CAR CLINIC: The engine is not always to blame - Daily Nation

CAR CLINIC: The ignition may be the reason why your car has stalled

Wednesday November 28 2018

Black smoke means poor combustion or the result of over fuelling.

Black smoke means poor combustion or the result of over fuelling. PHOTO| FOTOSEARCH 

By BARAZA JM
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Dear Baraza,

I own a 2006 model Toyota Isis Platana purchased from Japan. For five years now, I have been driving without any major issues apart from the alternator and starter repair.

I have ran out of fuel only twice within the same years. Now, a top right-hand side engine mounting is broken [could you tell me how much it costs] and when I start the car in the morning, it emits black smoke for a while which smells like burning oil. My mechanic says the engine needs an overhaul but cannot guarantee this as there are issues in a viv D4 engines. What could you advice? Abdul

Hi Abdul,

I don’t know how much an engine mount costs; less so for a vehicle I have never owned.

My automotive knowledge does not extend to price lists of sundry parts, and cursory attempts at establishing this result in responses along the lines of “Let’s talk on the side” which means the price is not even standard — it appears that there is a different price for different people depending on who is asking and who is being asked.

I cannot bother going deeper if I do not intend to buy the said part at the end of the day. Sorry.

Black smoke means poor combustion or the result of over fuelling — when the injectors deliver more fuel than is necessary for a particular volume of air at particular valve and ignition timing intervals; or the fuel itself is of the wrong grade/quality.

None of these seem attached to an engine overhaul; you are more likely facing a sensor problem — oxygen or MAF (Mass Air Flow) — or leaking injectors, or a clogged air filter that is suffocating the engine, or an issue with the fuel pressure regulator. These just need replacement- they don’t call for an overhaul of the entire engine.

However, somebody somewhere tells me damaged piston rings could cause black smoke. I always thought it was blue smoke from burning oil, but they say black smoke is symptomatic as well, so per-haps you are due for an overhaul after all.

I know deposits within the engine could cause black smoke too, but we now live in an era of Shell V Power and Total Excellium fuels which have additional cleaning agents in them; you just need to top up with these fuels and run your engine for a while on this fancy juice instead of opening up the engine to clean out the deposits manually.

Do an “Italian tune-up” while at it — sustaining high engine speeds for a while — for maximum effect but now this is the point at which we run into a dilemma.

If the problem is from deposits within the engine, an “Italian tune-up” with those exceptional fuels will solve your problem pronto. However, if the problem is from damaged piston rings, the “Italian tune-up” is just going to make matters worse, irrespective of fuel type. So now what?

I have placed all the cards on the table for you; now make the call. I will not choose a course of action for you because on one hand, you may overhaul an engine that only needed V Power or a sensor replacement to work fine.

This is like doing open heart surgery on someone with a bad cough simply be-cause the problem emanates from their chest. On the other hand, you may do an “Italian tune up” on an engine that actually needs an overhaul and find yourself in the market for a whole replacement engine. I will not be held liable for such undesired developments.

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Does driving in sport mode consume lesser fuel compared to drive mode?

Hi JM

Kindly assist me. I have a Subaru Impreza new model 2010. It happens that the fuel consumption while on a highway is less while in sport mode and more consumption in the drive mode. This has made me drive in sport mode while travelling long distances and drive while in town. Please advise - is it okay or could there be a problem? Moses

Hi Moses,

I’m sorry, but I’ll have to ask for more details on how you arrived at this conclusion, the first question being: was your test scientific? That is, did you keep all factors constant — same route, same load, same conditions — except for the driving mode?

How did you calculate the fuel consumption? Finally, what is the difference in consumption figures? Is it marginal or is it something you would expect from two completely different engines, let alone driving modes?

In nature, Sport Mode should be thirstier — barely so — than Normal mode, so if the reverse is true, well, something is off, and not the mode. I can’t say at the moment what exactly, unless and until I have a comprehensive description of how this experiment was carried out, or I do it myself; and the odds of this happening are slim to none. Not for the first time will I declare: I am not a mechanic.

In the meantime, try and repeat the experiment, this time with a keen eye on parameters both variable and constant. I strongly suspect nothing is wrong with your car; something else is at play here and could be as benign as suggestibility on the observer’s part or as malignant as the need for a software patch for a glitchy operating system.

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A fan stands next to a 1930 Ford Model A on display during the 2018 Concours D’Elegance.

A 1930 Ford Model A on display during the 2018 Concours D’Elegance. PHOTO | FILE| NATION MEDIA GROUP

Why are classic cars ‘smelly’

Hi, I love driving classic cars and most of them have a smell of unburnt fuel. What is the remedy to this issue? Leon Mariga

Hi Mariga,

The stench of petrol in old cars may come from worn-out hoses and seals due to age; and replacing them all may be a bigger undertaking than may seem at first glance.

The smell could also come from incomplete combustion — due to old plugs — which is an easier circumstance to remedy: just yank the current spark plugs and install new ones. For some people, that smell of un-burnt petrol is strangely attractive. I do not know what to say to this.

***

Why will my Duet not start even with a new engine?

Dear JM,

I am based in Mumias and I have a 2002 Toyota Duet in good body shape. The last time I drove it into the parking yard, it refused to start the following day. Initially, I thought the battery was low, but jump-starting could not work.

So I brought in a mechanic, who after electronic troubleshooting, told me that the computer box had a problem. It was established by a programmer in Nairobi that the computer system did not have a diode but despite its replacement, the vehicle could not start.

I was advised to put another computer or another engine altogether (since it would come along with a computer box), I chose the latter as the engine was smoking anyway and would ultimately require overhaul. And now with the new engine and computer, the vehicle still won’t start and the mechanic tells me the check engine lights are not even blinking for troubleshooting to happen. He says the new computer could be faulty. I am confused and have abandoned the vehicle for now. Please advise me on what could be the problem. Ambongo.

Hello Ambongo,

Let us do a bit of Sherlock-que deductory analysis, or maybe Occam's Razor, shall we?

The mechanic came in and said the ECU (what you call the computer box) had a problem. How did he arrive at this conclusion?

The programmer in Nairobi said the computer did not have a diode — did the diode disappear overnight or how had the car been operating before it gave up suddenly? I know what a diode is.

I studied Electronics as part of my Physics class in high school — it is essentially a one-way valve for electrical current. So yes, a missing diode could fry the chip, but did this diode leave on its own accord?

Replacement of the diode did not help matters either, which leads to two conclusions: either the diode itself was never the problem to start with; or it was a case of shutting the door after the horse has bolted. The ECU was already dead.

So now, you not only got a new ECU but a new engine as well. Interesting, and not exactly unwise, since the old one was smoking and was due for an overhaul anyway.

A replacement Duet engine is cheap (relatively) so an overhaul can be safely overlooked without too much worry that the alternative amounts to overspending.

That much is settled; however, with a new engine and ECU (are you sure there was a new ECU?) the non-starting problem persists. Do you see what I see?

There is an obvious suspect here, and that is the ignition suspect when a car won't start (or has a hard start), after which we now look for the next two problem areas: does the engine have a spark and is it getting fuel?

However, with these two suspects, at least the engine will turn but not kick. I think from your description, your engine was not even turning, which leads us back to the starter.

Leave the engine and ECU alone and now look at other things, beginning with the starter. Is it functioning? Has it meshed with the flywheel or is it slipping?

Then check the ignition system followed by the fuel system; but don't buy any more engines or ECUs; these are unwarranted and admittedly very high expenses.

***

The Fielder.

The Fielder.PHOTO | COURTESY

Please guide me on which car to replace my Fielder with

Dear Baraza,

I am a keen follower of your articles about cars. I need your valuable opinion on these three cars, the Harrier-2.4l, the Vanguard-2.4l and the Subaru Forester XT.

I currently drive a Toyota Fielder and I am looking at upgrading to a car with more ground clearance, is fuel efficient, has off-road capabilities plus I don’t want a car that can’t do 45 kilometres off-road without complaining. I also want a stable car whose service parts should not be prohibitive in terms of cost. Thanks in advance. Regards, Kay

Greetings Kay,

Well, you are on the right path in terms of increased ground clearance but could be barking up the wrong tree in terms of fuel economy. These cars are not thirsty outright, but none of them will even come close to the Fielder in terms of consumption or the lack thereof. That being said, drive gently and you will be fine.

Off-road capability: it depends on what you mean by “off-road”. Watch out for the RAV4 and the Harrier. These sometimes appear in the market in poverty-spec 2WD trim; not all of them have AWD.

The Subaru has this base covered: All Foresters have (symmetrical) AWD as standard, meaning they will pound murram roads convincingly, but some (Subaru) more convincingly than others, especially when it comes to slippery mud. Deep mud will trap all three, sand is a no-no as is fording rivers and crawling over rocks.

These are not the vehicles for this type of adventure. Keep the off-roading light.

Stability — well, the symmetrical AWD comes into play again, but this can be matched with an aggressive enough stability control system which can be found in the other two, particularly the Harrier.

If you mean rollover risk, well, then, the Subaru wins again, just barely. It has a lower c-of-g but this difference is only discernible when doing the type of driving that you should not be engaging in anyway.

Maintenance costs will depend on how new the vehicle is. Newer cars cost more to maintain owing to increased kit and complexity. Servicing will depend on where you do it but Subaru plugs in general are known to cost a pretty sum over and above Toyota ones.

Now, going by your question, the standout requirement here is ruggedness (you have two references to non-tarmac usage: increased ground clearance and off-road capabilities, which you then reinforce with your 45 kilometre example) in which case you cannot go wrong with the Forester. This has been written here before, ad nauseam.

***

Having car trouble? Write to [email protected] for free advice.

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