Push start an engine...
 

I dropped off my car for the 30,000 mile checkup today, and as I was removing all the junk from my car before taking it there, I also took my owner´s manual from the glove box.

I started to flip through it, and came upon a section that talks about starting an engine if the battery is dead (as in: pushing it while in 3rd gear, and letting out the clutch to start the engine). It said that if you have an automatic, you can´t push start it (knew that).

But... it said that if you have a 5 speed, you can start it if it doesn´t have a catalitic converted (some countries don´t require the car to have one), but if it does have a cat, then you should NOT push start the car (just like if it was an automatic).

I thought you could. Does anyone know why the manual says you shouldn´t?

beyond me ,,, maybe the feal it will damage something ,, I have done it to my car , but in second gear
B

So have I... did it when the battery died after 2.5 years of owning the car. I was impressed with the lifetime of the battery.

Still... I don´t see a reason why we shouldn´t do it on a car with a cat.

Either way, I have removed my cat. So I really don´t care. But I still would like to know why they would say that in the manual.

My brother has a 90 Miata, he just a month or so ago, replaced the original battery.
I'm not sure why you "shouldn't" push start a car with a cat, but I've heard that it is because for some reason you will plug it if you do. Don't ask me how or why, but thats what I've been told.

From http://www.hintsandthings.co.uk/garage/emergency.htm

"Regarding the issue of towing and pushing cars with a catalytic converter, it is perfectly fine to tow a car with one. Push starting one may cause problems if the engine is turning and supplying petrol but not firing. The reason a 'cat' may get its life shortened (but not ruined instantly) is that unburnt petrol is getting on to it, which might happen from persistant push starting where firing does not occur. Push starting due to a flat battery only (i.e starter won't turn) should be fine as the engine should fire as soon as it would when started normally.

One way of prolonging catalytic converter life is to avoid revving or blipping the engine before turning it off as this leaves unburnt fuel on it. By letting the engine idle for a few seconds before turning off lets it settle. Also very short journeys reduce its life as it doesn't get upto temperature."

Don't see why it could cause an immediate problem... I've push started a few cars at work cause I was too lazy to get the booster. Worked out fine!

Thanks Toru. :)

We've had -25C...-30C now since christmas and there have been many dead batteries. In tv they warned NOT to tow/push start new vehicles. There have been many broken timing belts (mostly because the weather + towing) and catalytic converters. Just like Toru wrote/borrowed, cat MAY get unburned fuel and when the engine starts the fuel explodes in the cat and may ruin it.

Well, fortunately the weather forecast gives much warmer now, like -15C for couple of days and for the weekend, -25C again. That really starts to piss me off . Just lucky that both our Mazdas are quite warm and they do start. ;)