My ‘5’ is going in for its MOT tomorrow, and a quick service.<o:p></o:p>
I have a problem with the fuel economy at the moment. On a full tank of approximately 35 litres, I’m getting about 170 miles! <o:p></o:p>
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Is that right? The car smells strongly of fuel when it starts, and appears to be running very rich.<o:p></o:p>
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I’m used to cars getting about 350-400 miles of a full tank.<o:p></o:p>
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I did have a mobile mechanic come round and swap an s/s exhaust, and de-cat pipe. I know he didn’t adjust the lambda sensors, and that they’re both reading differently and that it’s causing the engine to run ‘lumpy’. Would that be part of the reason???<o:p></o:p>
The garage are fixing the oxygen sensors tomorrow, but just want some advice on what could be causing the bad fuel economy before the garage try and bamboozle me into spending more than I’ve got!<o:p></o:p>
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And may I say…I don’t floor the car everywhere. On the odd occasion I’ll let it go, but 95% of the time, it’s just a gentle cruise to and from work!<o:p></o:p>
I make that about 22mpg which is not good, I get 28+ (1993 1.6 Eunos) driven quite hard,but can not offer any advice on what may be wrong, but if it was running OK before the visit of the mobile mechanic I would get him back and get him to sort it.
Can’t quite understand oxygen sensors[plural]? There is only one on a '91 car and that’s fitted into the exhaust manifold, your mobile fitter may well have damaged it when replacing the manifold.
As far as I know they are not adjustable in any way, they just send signals to the ecu re exhaust gas mixture.
Bad consumption is a regular topic here, with a variety of causes, from blocked air filters, though knackered injectors[very rare] o2 sensors failing, the most common one however appears to be binding brakes.
Check all 4 wheels after a run, see if the centre of one is hotter than the other. After a gentle drivethee should not be a lot of heat in the brakes.
Also as you are driving an auto most of them return worse fuel economy than a manual transmission
Yes, I’d love to know what they’re going to do to “fix” the heat sensor/fuse on the catalytic converter. Besides it not actually being a Lambda sensor, its not available here. Visions of a cat being drilled/retapped spring to mind…
22-25 mpg is about par for the course for a Mk11.6 automatic. They are never spectacularly good (manual 1.6 will typically get 35-40mpg+). As Geoff indicates, perform the usual servicing tasks, and eliminate handbrake binding.
The garage couldn’t find anything wrong with the fuel mix, and reckoned that there was nothing else he could do…but suggested if I’m still unhappy and think it’s running lumpy, to take it elsewhere.
The emissions, which I was worried about since having my cat removed, ended up being 0.60% CO. Way under the maximum limit, and he reckons if anything the car is running a little lean and not rich.
So after getting my little car back, it was roof down and a quick blast in the country for 40 minutes - a full quarter of a tank later [:S]
All it did fail on the MOT was the rear fog light switch had no light to tell whether it was on or not. So £50 later…I’ve the got the MX5parts switch fitted, which when switched on…still can’t see any light anyway!
To continue with the theme, I’ve got a '93 1.6 NA, and since I’ve had it it’s returning 25 - 28 mpg which is pretty dissapointing I think. I’ve checked for break rub and don’t think that’s the problem and I’ve just changed the thermostat in a bid to improve the economy (thought maybe it was not opening properly and therefore the choke was staying out) and cleaned the airfilter (though it wasn’t terribly dirty). I’ve had the car serviced since I’ve owned it. I’ve jsut calculated 25 mpg on a tank of shell superunleaded, which is actually the worst figure it’s returned. The only other thing that I think might be material is that the heater matrix isn’t very good - the blowers only manage a medium heat…
Any ideas anyone?
I absolutley love the little beast, but I can’t afford 25 mpg!! (Already got a gaz guzzling CR-V as a family car!)
It’s an import so take a look down the petrol filler pipe and see if it’s got an unleaded converter in there. A thing to reduce the size of the inlet so you can’t accidentally put leaded fuel in - not that there is any, any more.
An importer had fitted one to my mates car but hadn’t pushed it fully home. The petrol cap would tighten up onto the top of the converter but was still about an eighth of an inch short of sealing the top of the pipe.
Consequently, anything over two thirds full, come to a roundabout or a series of bends and the petrol would slosh out = poor fuel economy and stinking of petrol!
We only found it when we were playing follow my leader on the way to Silverstone and it was his turn to be in front I saw it sloshing out as we went through a series of S bends.
He removed the adaptor altogether = improved fuel economy, no more petrol smells
He’d been putting his poor fuel economy down to his supercharger. Once the filler was fixed, economy was on a level with pre-supercharger days - if he was careful
I saw it sloshing out as we went through a series of S bends.
