Hot weather misfire?

consumers_revenge

Hi,

The car started mifiring on a short journey back from dropping dd at nursery this morning.

Car perfect when going around last night. Can sit at a steady rev in neutral no issues. Hasnt dropped any water, reserve in same place. Cant see any wires or caps off under angine.

Only around £5 in the tank as light has just come on.

Wondering if this is anything to do with continual hot weather? Petrol likely to evaporate? Air filter cant breathe etc?

westwood68

Depends how old it is and what car it is. Could be a multitude of things but electrics in the ignition side if things tend to start failing when they get hot.

I'd say check one of the coils if it has them but by the time the car cools enough to handle it safely, it would probably be working again

motorguy

consumers_revenge wrote: »

Hi,

The car started mifiring on a short journey back from dropping dd at nursery this morning.

Car perfect when going around last night. Can sit at a steady rev in neutral no issues. Hasnt dropped any water, reserve in same place. Cant see any wires or caps off under angine.

Only around £5 in the tank as light has just come on.

Wondering if this is anything to do with continual hot weather? Petrol likely to evaporate? Air filter cant breathe etc?

what sort of car is it, engine, age, etc?

consumers_revenge

Sorry was in a rush to get off to work.

Its a ford focus 2000 w reg zetec petrol. About 95k on the clock. Used a couple of times a week ( flawless ) as have a bike. Prob hasnt had the air filter or plugs changed ( due to little use ) for anywhere up to 2.5 years now.

Engine ussually quite responsive. The only thing I noticed yesterday ( no misfire ) was that it wasnt very responsive when I put me foot down hard yesterday from 15mph. Ussually more responsive.

Cheers.

Technical_Dave

I betting it's the air flow meter or MAP sensor (it will only have one - different system, not sure which a zetec uses).

rochja

In the 'olden days' the most likely fault was an HT lead problem. Before going to great expense I would have found out if the misfire was limited to one cylinder by disconnecting the HT lead to each cylinder in turn to see if the problem got worse or stayed the same. When it stayed the same I had identified the misfiring cylinder. I could then clean/adjust/replace the spark plug and if no satisfaction replace the HT lead. Playing with HT leads could be a thrilling experience. There was also the problems associated with points gaps and distributor caps and rotor arms. I don't know if the EMU's act to invalidate this as a test system now though. God I feel old.

consumers_revenge

Could a garage do a quick diagnosis on this?

Just googled both MAF sensor and MAP and it has pages for both - is there only one?

colino

Before lashing out on anything else, why not put £20 of fuel in. It's bad practice to keep a low reserve anyway and with no heat sink in the tank of fuel, you'd certainly increase your chances of fuel vaporisation. More likely just needs a service though as parts of mainland Europe and further afield with similar spec. cars with consistently hotter weather aren't spontaneously breaking down or bursting into flames.

Ultrasonic

consumers_revenge wrote: »

Prob hasnt had the air filter or plugs changed ( due to little use ) for anywhere up to 2.5 years now.

This won't fix the current issue, but has the car had an oil change in that time? If not you probably ought to get that done. Only doing occasional short trips in a car actually means this should be done more often.

mattyprice4004

Get some fuel in it, and make sure it's actually a fault.

consumers_revenge

Again it ran fine til engine got hot then started probs again.

Looking like its the coil/plugs/leads. Thinking back now there has been 2-3 in the last couple of months when the engines turning over cold and it just wont start, leave it 10 secs and its starts fine.