MPG (not good...)

[philmar]

Any ideas on why my mx5 would only be doing about 16-18 mpg (driving sensibly!)? I thought it would improve when engine changed...

[Fruitcake]

Sounds to be over-fuelling. Take the plugs out and see how black they are. My bet is very.

Does it choke itself easily too?

[franv8]

Have you done a diagnostic? Sounds like an iffy sensor or sensor not reconnected (first checks would be the o2 sensor in the exhaust downpipe - connects to a small single wire connector on top of the coil pack, second would be the ECU temp sensor - try round the back of the block underneath the coil pack. There is two there - I believe it is the one with the large square plug)

[pmanson]

franv8 said:

Have you done a diagnostic? Sounds like an iffy sensor or sensor not reconnected (first checks would be the o2 sensor in the exhaust downpipe - connects to a small single wire connector on top of the coil pack, second would be the ECU temp sensor - try round the back of the block underneath the coil pack. There is two there - I believe it is the one with the large square plug)

I've just changed the 02 sensor on ours and it seems to have made a difference.

Usual things to check - plugs, plug leads, sticky caliper somewhere?

[philmar]

pmanson said:

franv8 said:

Have you done a diagnostic? Sounds like an iffy sensor or sensor not reconnected (first checks would be the o2 sensor in the exhaust downpipe - connects to a small single wire connector on top of the coil pack, second would be the ECU temp sensor - try round the back of the block underneath the coil pack. There is two there - I believe it is the one with the large square plug)

I've just changed the 02 sensor on ours and it seems to have made a difference.

Usual things to check - plugs, plug leads, sticky caliper somewhere?

Sticky caliper - yup, although it seems not too bad at the moment - im not using the handbrake at the as it would be very stuck...

I have it booked in for a service on Wednesday so will ask them to check all this & hopefully improve things no end. Plugs I imagine will need changing as its stuttering a bit too (and will be caked in all sorts from the old engine illness).

Another question... The oil pressure guage doesnt work. When ignition is turned on the needle shoots to the top, then when i switch the engine on it flicks straight to the bottom. It was working fine before... any ideas???

Can you tell im not having a lot of luck with this car

[pmanson]

Stuttering is probably knackered HT leads. Well worth changing them at the sametime as the plugs

[philmar]

will add to the list

[NiceCupOfTea]

If you have changed the engine there was a change in the oil pressure sender in about 94 - earlier ones are proper senders, later ones are a worse than useless digital affair that showed "none" or "some" a light would have been better.

Maybe if you didn't swap the sender you went from one version to the other?

[philmar]

NiceCupOfTea said:

If you have changed the engine there was a change in the oil pressure sender in about 94 - earlier ones are proper senders, later ones are a worse than useless digital affair that showed "none" or "some" a light would have been better.

Maybe if you didn't swap the sender you went from one version to the other?

Its a 94 car, the needle used to work nicely, moving about when accelerating and easing off etc (or when the engine was struggling ), now just nothing at all, flicks up to the top when ignition is switched on, then flicks to bottom when engine is on. Nothing inbetween. Less than useless!

[anonymous-user]

I only get 230 miles to a tank (driven sensibly)

My maths works that out at 26mpg - is that normal? I got more than that in my Clio 172 driven 'enthusiastically'!

Does it need looking at?

[princeperch]

Mac. said:

I only get 230 miles to a tank (driven sensibly)

My maths works that out at 26mpg - is that normal? I got more than that in my Clio 172 driven 'enthusiastically'!

Does it need looking at?

Blimey.

A comparison with my car maybe isn't particularly fair as I have the weedy 1.6 which no doubt gives a little bit more economy, but the most I have ever got out of a full tank doing almost 100% motorway driving (keeping her below 4k rpm), was 340 miles.

I was fairly chuffed. I reckon I could have got her to 350 but that might have been pushing my luck...

[Chris71]

Mac. said:

I only get 230 miles to a tank (driven sensibly)

My maths works that out at 26mpg - is that normal? I got more than that in my Clio 172 driven 'enthusiastically'!

Does it need looking at?

My RS-LTD managed low 30s mpg in every day driving and at the time I was surprised to see this was one of the more frugal examples out there, so 26mpg sounds about right if you get a few more chances to open it up.

(Tempted to get another one, hence the lurking...)

[skinny]

driven 'normally' i get around 32mpg in my 1.6 turbo.

[snotrag]

Mine seems to average at 28-30ish, for a '94 1.8 which I think could do with a bit of a service and tune-up.

[Fruitcake]

Mac. said:

I only get 230 miles to a tank (driven sensibly)

My maths works that out at 26mpg - is that normal? I got more than that in my Clio 172 driven 'enthusiastically'!

Does it need looking at?

Driven sensibly? Are you sure?

I get about that, with my kind of driving...

I'm not fast, just heavy footed, by the way!

[anonymous-user]

I'm taking it really steady this week on the motorway to see what I can get out of her. Will report back when I'm on empty

[MX-5 Lazza]

The only way to check mpg is to fill up - drive till nearly empty then fill up again.
(Miles / Litres) * 4.54 = mpg

This thread, like so many others on the mpg theme is a bit pointless though other than the OPs post (16mpg is very bad. I only dip below that when I'm driving on the track!). We will all get very different mpg as we all drive in different ways on different roads at different times of day etc. It would be more surprising if we all got the same mpg!
If I do my normal day-to-day driving in my silly power SC '5 I get around 25mpg. If I'm really careful I can get 27mpg. This is 100% country lanes & B-roads. If I get a chance to stretch it's legs a bit with some motorway driving like when I visit my folks in Norwich I can get 35mpg. On the track I can get it as low as 10-12mpg

To the OP I'd say you have to do a bit of servicing and replace some of the sensors, plugs, leads etc.
I'd start with plugs & leads and the O2 sensor. If the thermistor was faulty you'd probably get a misfire.

[tuglet]

philmar said:

Any ideas on why my mx5 would only be doing about 16-18 mpg (driving sensibly!)? I thought it would improve when engine changed...

Mk1 1.8 Eunos Roadster used as my daily driver. I'm averaging about 16mpg from each tank of unleaded, but I only live a couple of miles from work so she's not even getting a chance to warm up. On the rare occassion she gets a long run out, the average mpg improves very quickly. Best I've seen is 26mpg.

[MX-5 Lazza]

tuglet said:

philmar said:

Any ideas on why my mx5 would only be doing about 16-18 mpg (driving sensibly!)? I thought it would improve when engine changed...

Mk1 1.8 Eunos Roadster used as my daily driver. I'm averaging about 16mpg from each tank of unleaded, but I only live a couple of miles from work so she's not even getting a chance to warm up. On the rare occassion she gets a long run out, the average mpg improves very quickly. Best I've seen is 26mpg.

I know this is PistonHeads so it's probably sacrilege to say this but... why don't you walk?

[Fruitcake]

MX-5 Lazza said:

tuglet said:

philmar said:

Any ideas on why my mx5 would only be doing about 16-18 mpg (driving sensibly!)? I thought it would improve when engine changed...

Mk1 1.8 Eunos Roadster used as my daily driver. I'm averaging about 16mpg from each tank of unleaded, but I only live a couple of miles from work so she's not even getting a chance to warm up. On the rare occassion she gets a long run out, the average mpg improves very quickly. Best I've seen is 26mpg.

I know this is PistonHeads so it's probably sacrilege to say this but... why don't you walk?

Indeed. Last time I looked walking was free and so's cycling, come to that.

I'd love a job where I could cycle to work.

It's too far though and I need a car for while I'm there