My wife's 1995 1L Micra (16V) does this as well occasionally if moved from the street to the drive etc. The cure is exactly as described above. It always seems more likely to occur in winter than summer, so I wondered if it's a cold starting enrichment problem.
With this in mind, the last few times I've stopped the engine after a 30 second run, I've held the revs at about 3000 RPM for a few seconds, then cut the ignition with the accelerator held in place.
I know the manual says not to do this, but it also says not to continue cranking if it won't start.....
My logic is that the fuel flow stops as soon as you turn off the ignition, but that the engine costs on for a few more revs, pumping air through the cylinders and removing any remaining petrol.
I can't really confirm if this works (yet). What does everyone think?
Ian
|
My logic is that the fuel flow stops as soon as you turn off the ignition, but that the engine costs on for a few more revs, pumping air through the cylinders and removing any remaining petrol.
And the petrol also washes away any remaining oil in the cylinder bores as well. So next time you start your engine, for a few seconds there is no lubrication in the bores - hence the "cold start" syndrome.
Revving the engine prior to switching off does the engine no good whatsoever.
|
>> My logic is that the fuel flow stops as soon as >> you turn off the ignition, but that the engine costs on >> for a few more revs, pumping air through the cylinders and >> removing any remaining petrol. And the petrol also washes away any remaining oil in the cylinder bores as well. So next time you start your engine, for a few seconds there is no lubrication in the bores - hence the "cold start" syndrome. Revving the engine prior to switching off does the engine no good whatsoever.
But if Dave's theory is correct, there won't be any petrol to wash the oil off with, because the pump will have been off for a second or too. In fact logically, there would be oil NOT washed off, as would occur normally, so in fact reving ought to be beneficial.
Revving in the old days was intended to give a charge of petrol, supposedly to assist starting next time.
This was obviously harmful. But cutting off the fuel before the engine comes to rest, and giving a spray of oil from the revving con rods, sounds on the face of it like a good idea.
Is there a snag here?
|
But if Dave's theory is correct, there won't be any petrol to wash the oil off with, because the pump will have been off for a second or too.
And the spark plugs will also have been off for a second or two. So how is the petrol you've squirted into the bores going to combust?
|
|
|
|
There is a modification to the coolant temperature sensor circuit on the 16v Micra which is designed to prevent this problem happening.It is available from Nissan and is reasonably easy to fit.Ask your local dealer.
David Davies (Tune-Up Raglan)
|
Thanks for the advice, but I'm afraid we had this modification done the first time the problem happened. It seemed to make no difference. Given my experience with Nissan dealers, you do wonder if they actually did it though...... Do you know if there's a DIY way to tell?
Referring to the earlier discussion of revving the engine as you turn off the ignition, I'd guess that the injectors stop firing as soon as you turn off the ignition key. As a result, you shouldn't get any more build up of fuel in the cylinders than normal should you? I guess it might take a couple of seconds for any fuel left over from the acceleration enrichment to be dissipated, but the cold start enrichment is probably lower at this engine speed.
I know that revving a cold engine isn't any good for it, but we're also talking about a few seconds at about 3000 RPM. How damaging is this compared with cranking a cold engine for several minutes? Don't forget that the highest loadings on a cam shaft lobe tips are at the lowest engine speeds.
Thanks
Ian
|
Could this be a cold climate issue? My two vehicles are both catalysed and I frequently start and stop them for a few seconds at a time for manoeuvring. I have never had any of the problems described above, could this be because of an ambient temperature 28-34C year in year out?
I just went outside and did it again to see if I could reproduce the above (probably not very clever!) but yep they both cranked up no probs each time.
One would have thought technology would have produced the whit by now to solve such a basic problem!
|
Could this be a cold climate issue? My two vehicles are both catalysed and I frequently start and stop them for a few seconds at a time for manoeuvring. I have never had any of the problems described above, could this be because of an ambient temperature 28-34C year in year out? I just went outside and did it again to see if I could reproduce the above (probably not very clever!) but yep they both cranked up no probs each time. One would have thought technology would have produced the whit by now to solve such a basic problem!
The problem seems to be make/model/year specific, and may be ambient temperature related.
It is probably due to some software not having taken account of the fact that people sometimes only run their engine for a few seconds to drive a feet feet.
|
|
Always make sure your car is thoroughly warm before turning off the ignition;if you're washing the car drive it round the block before you put it away;it wwill get the water out of the seams on the body as well as making sure you're off the "start" procedure.
|
|
|
|
|
|
