Why does my car produce smoke in the morning?

Friday December 2 2016

The exhaust system cleans out gases making them

The exhaust system cleans out gases making them safe and cleaner for the environment. Photo by Alex Esagala. 

By Paul Kaganzi

Dear Paul,

My Toyota Landcruiser Prado 4.7 petrol releases a lot of smoke in the morning from home, even then I just serviced the car. What could be the problem? Karim

Dear Karim, you need to observe the colour of your the smoke. It would be wise to also confirm whether the exhaust continues to bellow a lot of smoke even when your engine attains the normal running temperature above 80 degrees centigrade.

Your car must produce smoke as a byproduct of the engine combustion process (burning of the fuel air mixture). The quality (colour) and quantity of smoke will tell a lot about the working condition of your Toyota.

The colour of smoke will be different according to the different faults in your engine. Blue smoke is often caused by broken piston rings or damaged valve stem seals which allow engine oil to infiltrate the combustion chamber and get burnt with the fuel air mixture.

Given your recent engine oil service and the suggestion that the smoke is only excessive shortly after the cold engine starts I think your car produces black smoke.

Excessive black smoke from your exhaust is often caused by the presence of an imbalanced fuel air ratio with more fuel than air (running rich) in the combustion chamber.

There are several causes of this situation: excessive buildup of dirt in the air cleaner, failure of the throttle valve to open fully or due to the buildup of soot which prevents free and prompt engine air in-flow and the buildup of appropriate fuel air ratios.

On the other hand leaking or malfunctioning fuel injectors may deliver too much fuel while failure of engine management components like the oxygen sensors will cause a delivery of more than enough fuel.

Some of the above faults or features may occur regardless of whether you have carried out the routine engine oil and filter service or not.

In case your exhaust smoke is black but reduces when the engine is hot, it may be because the engine’s cold start idling revolutions have slowed down after the engine warming up.

I have a Toyota Corona ST190 (Kibina) which has a problem of failing to start at first attempt but will start on the second attempt. After running for some time when you stop and park for 30 to 40 minutes, it again fails to start at first attempt. Charles

Hello Charles, the common causes of a failure to start the car on first attempt can be either of these: dirty or loose battery terminals, a damaged starter unit or a dirty/damaged throttle valve unit.

Dirty, corroded or loose battery terminals can prevent prompt starting; they should be inspected carefully and cleaned or tightened where necessary.

A damaged or worn out starter bendex is a strong likelihood in your case. You must find a good car electrician to dismantle your starter motor and inspect the bendex for possible wear.

If found worn out that should be replaced or the whole starter motor replaced in the event that the required parts are unavailable.

Lastly, should the battery terminal and starter motor be okay, another possible cause of the starting problem can be a dirty or clogged throttle valve. The throttle unit regulates intake air into the engine.

If the throttle valve movement is restricted due to soot or deposit build up or damaged, it will prevent prompt air intake and ignition.

Ask your mechanic to look into these three areas and one of them will be the trouble causer.

Tel: (0772316145), send sms: mycar (space) your comments and questions to 6933, or email them to [email protected]

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