Poor Fuel Economy

[john-melbourne 6]

Hi Guys,

 

I recently bought a CTI and drove her home about 200 mile all motorway journeys, during this journey I used a full tank of fuel which was about 50 quid. After doing some research and reading I replaced the ecu temp sensor in the hope this would solve my problem.

 

At the start of this week I put 30 quid in and have drove just over 100 mile and its all gone again!

 

Any suggestions for trying to improve my fuel economy? car is not so good at cold starting and hunts for an idle and sometimes stalls till warm. I have also replaced the SAD for a known working one.

 

Any more suggestions?

 

Thanks

 

John

[GLPoomobile 958]

I'd suggest doing some proper calculations of your consumption based on brimming the tank and working out how much fuel you've used between refills. £30 get's you d*ck all these days.

[Alan77 78 1 Cars]

At the peak of my goosed head gasket, before getting it seen to, I was getting 220 miles per tank!

Got it fixed and also put in a new ECU temp sensor and i'm now back to 350 miles per tank.

It might be something else but just a thought...

[GLPoomobile 958]

Going back to the first post, your 200 mile journey sounds like about 25mpg if I make some assumptions, but as I said, you really need to do some accurate calculations rather than just saying "I did 200 miles on £50 of petrol".

 

Poor economy, trouble starting, and hunting idle all sound like symptoms of it running rich. You can adjust the mixture screw on the AFM but that will ONLY adjust your idle mixture. Adjustment across the range can be made by opening the AFM and changing the spring tension, bu that's not something you piss about with unless you are sure you know what you are doing.

 

It could still be a problem relating to your temp sensor. The sensor itself is only one part of the equation. If there's a poor connection back to the ECU, you'll have the same issue as if the sensor was duff/disconnected. So check that the terminals are secure in the plug, that the plug is secure on the sensor, and that the wiring looks to be healthy. And one thing you could try - start the car and then immediately disconnect the plug to the temp sensor. Do you see any change in idle behaviour when doing this?

[dcc 855]

Does it it have a stupid FSE power boost valve (bloody stupid things)

 

Rather than fuel being injected at say 3bar, it is now injected at 3.5 (for example)

 

so if your injectors are firing at lets say 170cc/m, an extra 20% or so fuel being used means your chewing through more fuel for no good reason.

 

Ofcourse if it is not this then i am likely to be talking ouot of my arse.

 

If it were my car, I would get it taken to a friendly garage and see what the emissions are at.

 

removing the ECU temp sender and replacing with a known good one will be a great help too.

[steve@cornwall 100]

Of course, If you're driving it hard......

[john-melbourne 6]

Does it it have a stupid FSE power boost valve (bloody stupid things)

 

Rather than fuel being injected at say 3bar, it is now injected at 3.5 (for example)

 

so if your injectors are firing at lets say 170cc/m, an extra 20% or so fuel being used means your chewing through more fuel for no good reason.

 

Ofcourse if it is not this then i am likely to be talking ouot of my arse.

 

If it were my car, I would get it taken to a friendly garage and see what the emissions are at.

 

removing the ECU temp sender and replacing with a known good one will be a great help too.

Does it it have a stupid FSE power boost valve (bloody stupid things)

 

Rather than fuel being injected at say 3bar, it is now injected at 3.5 (for example)

 

so if your injectors are firing at lets say 170cc/m, an extra 20% or so fuel being used means your chewing through more fuel for no good reason.

 

Ofcourse if it is not this then i am likely to be talking ouot of my arse.

 

If it were my car, I would get it taken to a friendly garage and see what the emissions are at.

 

removing the ECU temp sender and replacing with a known good one will be a great help too.

 

I have replaced the ECU temp sensor, and not noticed an improvement

 

John

[GLPoomobile 958]

I have replaced the ECU temp sensor, and not noticed an improvement

 

John

 

....and as I said in my last post, it may not be the sensor that is duff but rather the connection or the wiring to the sensor, meaning it's not sending a signal to the ECU.

[Slo 283 1 Cars]

have you checked for rusty fuel pipes leaking near the tank ive just noticed the off whiff of petrol last day or so on my cti, is yours the 1.6?

[john-melbourne 6]

Hi Slo,

 

Yea its the 1.6.

 

John

[eastlondonpug 6]

Maybe worth checking the vacuum advance pipe on the distributor. My economy definitely improved a bit after replacing the perished pipe.

[omega 82]

want better mpg?

 

 

 

 

 

 

buy a diesel :D

 

 

 

its a 1.6 with i pressume a 1.6 box so the revs at moterway speeds will be high so not very good for mpg

the fuel gauge should not be taken as gospel as it tells lies

give it a good service eg plugs/air filter

make sure all the wheels are spinning free

if all the above fails then all i can recomend is drive it like a granny but if you going to do that then you wont get the fun/grin factor which is what a 205 is all about.

[petert 550]

Vacuum advance module on dizzy could be broken. Most are these days.

[c_robinson 8 1 Cars]

i had a split shortening pipe from filter to air flow meter that lead to massive overfuelling and mpg of about 6mpg on a stage rally car when i'd have expected 15-20mpg. Check for obvious airleaks, however an emissions test should help too.

Charlie

[Teacher 0]

Managed 47 mpg on a 301 mile trip to newcastle and back @ £138.9/litre. Engine is a 2.0 8v (from a 306 xsi) running on 1.9 management with a 1.6 box. Driving like a nun though i must admit!