HI guys.

I have noticed that my fuel economy is getting worse. I'm only getting about 270 miles out of a full tank. I don't know what that is in MPG on a Cento but I feel my car is robbing me. Here is a photo of my dash today. As you can see, the needle is just below 3/4 and the trip shows I haven't done that many miles since I reset it when I last filled the tank. I also haven't been driving the car hard due to the rear tyres being extremely iffy. Getting them changed on Friday though. Any suggestions or ideas?

iffy tyres? they could be causing it? not driving it much, implying short journeys - not good for mpg.

could be handbrake catching, are the drums hot to touch after a drive. could be low tyre pressures, could be faulty lambda or map.

Economy does get a lot worse in the winter because it takes longer for the engine to warm up.

My fuel gauge was doing strange things today - when you put your foot on the throttle, you actually could see it dropping, then you'd take it off and it would go back up. It now varies somewhere between fuel light off and empty

mine does that.. ive got used to it and have only run out of fuel the once. and that was when it first started acting up!

im just hoping its nothing more serious

It does look bad, I can almost see the needle dropping in the picture

Nah, I don't think 270 miles is too bad. I don't get much more than that from my 899cc Sei. I don't do very long trips though.

My 899cc Sei will do over 330 miles to a full tank. erm, is the oil dipstick in properly? or How about resetting the ECU as I did this with mine and it runs better now on a refreshed memory.

If you have any "performance enhancing" products such as filters or exhausts they willl start to rob you. Make sure you are putting the correct grade of oil in the car this can seriously effect your mpg.
Also other things like lots of weight in ya boot say a huge mdf build will put it up a little.
Another problem is in winter you are using your heater, rear screen demister, lights wipers possibly a.c. All of these things make your alternator have to work harder and therefore your mpg lowers.
I think the worst thing is every time you fill up the petrol pump ups the price so your phycologically off to a bad start whats every body else think?

Cheers for all your suggestions guys. I guess it could be most noticable as I have had to defrost the car 3 times because it has been so cold and left it running for a while for the car to warm and them I have been driving and the choke seems to stay on for a while.

My rear tyres are s**te at the mo. Could this make such a big difference?

My fuel gauge on my old Cinq used to do the same after I ran out once. JUst before I part-exed it too it got to a point where for about the first 5 mins of driving it would stick on empty and twang up to the correct level. lol

How do I reset the ECU? Is it simple? HOw long does it take to "learn" on a Sei?

Sei-Mad said:

My 899cc Sei will do over 330 miles to a full tank. erm, is the oil dipstick in properly? or How about resetting the ECU as I did this with mine and it runs better now on a refreshed memory.

Click to expand...

If there is no tread left on the rear then less resistance so better fuel economy in theory not worse, come on Smurf, to reset he ecu....................use the search! Pete has put it up a few times, it's not easy 2 min job though.

Liam

Gaz: how many £££ worth of fuel is a tankful then? My Punto struggles to reach 200 on a £20 fill-up, it used to be a lot more, I'm pretty sure it's the lambda sensor, will find out when I fix the head gasket and bosh a new (well, secondhand) lambda in.

ECU reset on the Punto is a bit of an odd procedure in the Haynes, not sure if the Sei will be exactly the same but must be worth a try:

1. Run engine until cooling fan switches on, then off, then back on.
2. As soon as the fan comes on the 2nd time, switch engine off and disconnect battery (negative lead is safer). Leave disconnected for at least 45 secs for ECU to reset.
3. Reconnect battery, let engine tick over for min. 2 minutes, if it stalls then d/c the battery for another 45 secs and try again.
4. Drive for a few miles to complete the ECU's "learning" process.

cheers guys. ill have a fiddle in the morning and let you know.

on the fuel question, it takes about 38 litres to fill. im nt sure what kinda mpg im getting because I haven't worked it out.

i found that when i drove my cinq changing up quickly and not using much revs like a granny i got worse fuel economy than if i rag it to hell because them im not making it struggle

dont mean to sound pesomistic but is there any chance of the ecu reset thing going wrong like the ecu looseing its memory totally

Hi,
38 litres used in about 270 miles equates to 32 ish mpg, thats about the same as my 899cc cinq which is used a lot for town journey's, lots of stop start etc.

Hope this helps

Paul T

Hmmm, thats exactly what my Punto does at the moment - 32mpg. Thats whether its being driven in town, thrashed on country roads or just cruising down motorways at a steady 70... ish
I know for certain that my Lambda is f***ed though, so hopefully replacing that will sort it.

Hi,
Might be totaly unrelated to your problem, but when was the car serviced last, clogged air filter, sticky oil and gummed up plugs will all make a big difference to your mpg....

Thanks
Paul T

Aye my Mpi Sei is doing about 36/38mpg at the mo at well! Ireackon it's down to the colder/damper weather? It was getting over 50mpg back in the summer.Although it is running on 15/50 oil mebbe it's causing too much drag for the cold conditions? I will go back to 5/40 next,& see what happens.

well its all serviced by me. all is fine. just needs the plugs changing. had an oil change this week. i'll change the plugs tomorrow and see how it goes on the next tank before I fiddle.

smurfhead said:

How do I reset the ECU? Is it simple? HOw long does it take to "learn" on a Sei?

Click to expand...

As its already mentioned in the thread, its the case of disconnecting the battery from the neg terminal and leave it off. I had the feed off for 20 min when doing some work on the driving lamps that I am currently rewiring. Last fill I did this morning was £24.00 of fuel - to 30.8 Litres (77.9p/litre) and 325 miles, note I do drive like a mad nutter and at average 60-65 mph - and "slowly" working though the gears, unless overtaking and its 3rd to 50mph

When I had a issue with my 899cc Sei with poor MPG (60 miles to 1/2 tank of fuel) it was the air/vac escaping from the MAP sensor pipework (spit in the hose) - so basicly mine was flooding the engine with extra fuel and maked it hard to drive. Yours may be leaking? If so check the pipe work from the engine to a little box that is upside down by the ECU for any spits and replace if nessary.

Mike

right. changed the plugs. ill see how it fares now for the rest of this tank and see if the top quarter of the next one is similar in performance.

Just a quick question, when I disconnect the battery, if I decide to reset the ECU, should I expect to have any probs with my alarm system or immobiliser? Will cutting the battery for this long effect them?