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Help... Please. 2011 impreza 1.5


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Hi everyone. Need help.. Please. 

Recently bought a 2011 impreza with a 1.5 litre engine and with 78000 kilometers on it. 

Car runs great, except for LTFT around 9 to 10, 15 ignition timing and worst part is I get around 10mpg / 5.5 kmpl. A full tank of fuel only gets around 300 kilometers. LTFT at idle is close to 10 and goes down to about 7 when AC is turned on. When driving, LTFT is around 2 to 4, goes to 0 when accelerated to around 2000rpm at idle. 

Checked for vacuum leaks, (found none) smoke tested it too. checked and clean EGR valve, cleaned MAF Sensor, (which reads around 2.2 to 2.5 at idle with ac off, around 3 with ac on. Rpm at idle is smooth and around 650 with ac off and around 850 with ac turned on. Fuel flow shows around 0.8 liters per hour with ac off at idle and around 1.7 liters per hour with ac on. Reset ecu (removed negative terminal and left off for about an hour, 10 mins run, switch off, run 5 mins, switch off, etc) lambda sensor shows value of 1.0 at idle and voltage of around 2.2

Please help guys.. At wits end and have no clue what's going on. 

There is a slight hesitation off the line when accelerating but starts pulling hard around 2000 to 3000 Rpm. Strong exhaust smell, not necessarily a fuel smell but a stinging kind of smell. 

Any ideas anyone? 

Any advice would be very helpful and very highly appreciated. 

Thanks in advance. 

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After cleaning the EGR, now the lean condition is permanent at around +9 LTFT. Doesn't go down under throttle. 😞 goes down to around +4 at load when driving. EGR valve gasket was replaced after cleaning and also added some high temp RTV sealent just to be sure. Please anyone, any ideas? Thanks... 

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If your pre and post cat lambdas are showing logical readings to support ltft and not suspect or had any fault codes for them then it seems likely with your results so far that egr valve leak maybe internally valve not closing correctly and scavenging effect drawing intake air into the exhaust making the lambda sensors see a lean condition thus more fuel .
How does car idle ?
Is coolant and oil levels and appearance all normal .
exhaust smell is probably from rich mixture/contaminated-failing cat perhaps .
You could try a temporary block of egr for a test, might be an idea pull plugs and visual inspect tips to evaluate fuelling equal across cylinders .

certainly needs sorting pretty quick as going cost a lot in fuel and component damage from serious fuelling issue .

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Thanks Mr. B for the reply.


EGR valve I took off, blew into it and works one way, doesn't work the other. Meaning only blows air one way. Idles great, around 650rpm on the dot without ac turned on, around 800 with ac on. Timing advance is at 15 at idle, doesn't change at all at idle. Coolant, topped up and all ok, engine oil is at normal levels albeit a bit old as per previous owner. Viscosity seems fine, doesn't smell burnt and not dark in color. Only thing I haven't checked so far is the spark plugs. Can bad plugs be the cause? No misfire codes are thrown and can't feel a misfire when driving / idling as well. Will check plugs over the weekend. 

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Sure. Will do. Again, Thanks Mr. B.

Seems to be getting worse... LTFT at idle with AC off is around 10 to 11 now and with AC on, goes down to around 8 to 9.

Hesitation during initial acceleration (happened for the first time today, felt as if it was being choked) Had to stop on the gas to get it going. and then starts moving when relative throttle position is above 25% Absolute throttle position around 38%

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  • 3 weeks later...

Any ideas anyone?

Update, issue is still the same, although after removing and cleaning the throttle body, get up n go is better...

Fuel trims, no change. still high, around 8 with AC off and around 6 with AC off. Fuel consumption is also the same, about 300 Kilometres for a full tank of fuel.

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Did a smoke test and found a Crack in the air box just before the throttle body. Patched it, smoke tested again and no more leaks. 

Reset the ecu, Battery off, run the car for 10 minutes and then off, 5 minutes run and off technique. 

LTFT, started low, then slowly stabilized at around the same as before. 😞

Around 7 with AC on, around 10 with ac off. Goes down to zero when RPM is around 1500, comes back to high at idle. 

At wits end with this... 

OH and now there is a hissing sound from around the gas tank, thought it might be a leak from the evap lines. Checked the canister under the boot along with evap lines, unplugged the evap also, hissing sound still there and no leak from evap system. Maybe the fuel tank breather? Lot of vacuum inside fuel tank when engine is switched off (long sucking in air sound when fuel tank filler cap is opened.) 


Any ideas anyone on how to get the LTFT down and fix this frustrating fuel consumption issue? 

6 kmpl / 16.67 liters per 100 kilometers. 

That's what I'm getting. 

I used to get 8kmpl with my mustang GT! 

This Subi is driving me nuts... 

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