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Discussion Starter · #1 ·
Zafira b 1.6 xe1 96k petrol

For the last few weeks I've noticed my mpg getting worse.

Recap on whats been done last 9 months

New gearbox / slave.
egr channels cleaned
new spark plugs
oil / filter / air filter
New delphi coil pack
oil pump gasket
front cam shaft seals
cam cover
New thermostat wahler one with new sensor in it.
front 02 sensor changed was causing idle issue, new one cured it.
EVAP valve


The car just hasn't been been running right and my garage said they are at a loss.

Basically you know that clacking noise you get when you don't give it enough fuel and let off the clutch I'm getting that as I drive occasionally.

I notice my fuel needle moves about dramatically, then after leaving the car off i noticed its gone back up.

I'm have the feeling that this could be a fueling issue like the fuel injectors or something that can cause issues.

Brakes aren't binding, tyre pressuers are spot on and can't smell any petrol leaking anywhere.

I've spent so much on it this last 9 months and still not got to the root of this noise. That metal on metal clacking noise.

Would appreciate any help with this, hopefully theres some clues someone spots in all of this.
 

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I thought cars use less fuel in the warm as they get up to temp quicker ?

cars are not my first language 🙂
What makes you think you are using more fuel?
Are you looking at the mpg shown on the notoriously inaccurate trip computer?
 

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Discussion Starter · #9 · (Edited)
What makes you think you are using more fuel?
Are you looking at the mpg shown on the notoriously inaccurate trip computer?
my cars not fancy enough to have an mpg reading.

I’ve been filling my tank right up and the amount of miles driven is significantly less. Same route no change in driving style tyre pressures good. It’s about 90 miles I did notice a whoosh of air when I opened the gas cap.

And the fuel gauge needle is dropping like lead.

And that noise from the video above is slowly driving me up the wall. Happens after I take my foot off the clutch and then go on to gas. Never does it in the first 10 mins of driving on a cold engine
 

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That knocking noise you are getting sounds like pre ignition / detonation, somewhere bolted to the engine should be a knock detector, where it pulls ignition timing.
Also as someone said "air temperature" as warm air is less dense than cold and the amount of Ethanol in the fuel means you'll need more of it.
Noticed you've changed the O2 sensor, maybe the old one trimmed the fuel weaker and led you to believe this is the fuel consumption?
Or the new one giving an off reading? no doubt you can check the Lambda figures.
 

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Discussion Starter · #11 ·
That knocking noise you are getting sounds like pre ignition / detonation, somewhere bolted to the engine should be a knock detector, where it pulls ignition timing.
Also as someone said "air temperature" as warm air is less dense than cold and the amount of Ethanol in the fuel means you'll need more of it.
Noticed you've changed the O2 sensor, maybe the old one trimmed the fuel weaker and led you to believe this is the fuel consumption?
Or the new one giving an off reading? no doubt you can check the Lambda figures.
That’s some very helpful info for me to work off.

The pre ignition issue is top priority. As the spark plugs have been done and the timing belt and egr channels Would the next logical step be the knock sensor ? (Forgot to mention the egr valve was change too)

I also read heat can be a cause my water pump has never been changed I’m on 96k. That said Ive had no overheating or loss of coolant. No over hearing warning signs up either. I can hear the fans kick in usually when sat still in traffic and I guess my temp hits 113 degrees.

Learn’t something new about ethanol and hot weather!

I’ll double check the front 02 make sure it’s switching ok.
 

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2008 Astra Twintop 1.8 Z18XER
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Since the switch to E10 petrol, my fuel consumption has been significantly worse. I did start running it on the more expensive E5 as a test and it was back to normal, current fuel prices however mean I'm back on crappy E10!
 

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Discussion Starter · #15 ·
I agree something after market parts do the job but more often than not lately they have been the cause of many issues, no idea if quality is getting worse.

I’ll just use genuine from here on as its bitten me in the backside these last few years.

I guess the old man was right pay cheap pay twice .. I’ll not tel me though lol
 
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