Weird Acceleration

Posts specific to the 2.0 litre NA engine

Weird Acceleration

Postby mihai » Wed Aug 05, 2009 10:23 pm

Hi All,

Recently ive noticed that my car (MY07 2.0R) has flat spots in the acceleration only at certain times.

During constant acceleration, at 2000 rpm or 2500 rpm it feels like ive let off the accelerator even though its remained in the same position, or even been depressed more. Then when the rpm reaches 3000 or 3500, the power suddently comes back on, and the car accelerates like i expect it to.

I think its a misfiring issue, but have no idea what the cause is. The car had its service completed at 25,000kms (currently 33,000kms) and it was only purchased on the 29th of May from Docklands.

Its currently doing my head in as its so random.

Michael
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Re: Weird Acceleration

Postby Ric » Wed Aug 05, 2009 10:37 pm

Did you mention this when you had the service?
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Re: Weird Acceleration

Postby mihai » Wed Aug 05, 2009 11:01 pm

I havnt had a service since i bought the car. The due date/kms havnt come up yet.
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Re: Weird Acceleration

Postby wassell2381 » Thu Aug 06, 2009 12:25 am

is the car an auto?
coz if it is then the car hates it when its in a high gear doing low revs and then when depressing the accelerator they have a delayed response before changing down which gives the car more acceleration. That's all i can think of that happens with my 2.5 auto
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Re: Weird Acceleration

Postby mihai » Thu Aug 06, 2009 8:45 am

Nuh, its a manual. And its not a delay in response, its just that the power isnt there. As i said, the power is there until it reaches 2000rpm or 2500rpm and then the power dies. Then at 3000 rpm the power is back.
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Re: Weird Acceleration

Postby adz2.0r » Thu Aug 06, 2009 9:03 am

Same thing happens to my 2.0r, It is really annoying although It has not happened as much as it used to but I will be heading to subaru next week to get them to check it out.

I have noticed if I let it warm up it dosent do it as often and also changing to mobil high octane fuel has helped.
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Re: Weird Acceleration

Postby mihai » Thu Aug 06, 2009 9:17 am

I was going to take it today, then they quoted me $100+ just to diagnose. And after i realised the service is due this month, i cancelled. Ill get them to check it out at the service. Might try resetting the ECU. Dont think its a matter of the petrol, I use the Shell Vpower. Might try Mobil, or BP Ultimate.
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Re: Weird Acceleration

Postby sheppo9 » Thu Aug 06, 2009 9:57 am

This might help the pair of you;

Category: Technical
Region/Zone: National

Date: 12th January 2007

Distribution: General

Reference: SIB-T-002-2007
Subject: 2.0R (DOHC Engine) Impreza and 2.0R (DOHC Engine) Liberty Performance

1. To maintain factory specified performance levels in either an 2.0R Impreza or a 2.0R Liberty it is essential to use unleaded fuel with an octane rating of 95RON or greater.

2. Similarly, to maintain factory performance levels, the engine oil in the 2.0R Impreza and 2.0R Liberty must be either 5W30 SM full synthetic or 10W30 SM mineral (10W30 SM semi synthetic or modified mineral is also ok).

3. If you encounter a customer complaint of poor performance in a 2.0R Impreza or 2.0R Liberty please confirm both the fuel and engine oil are as specified above.

If the fuel and engine oil APPEAR CORRECT please proceed as follows;

a.) MT (Manual Transmission)
Connect the SDS ( Subaru Diagnostic System i.e. Subaru Select Monitor 3 ).
Drive the vehicle for 20 minutes to stabilise engine operation and temperature.
Conduct full throttle tests in 2nd gear from 1000 RPM to 3000 RPM.
View the SDS knock correction data in relation to the table below;

b.) AT (Automatic Transmission)
Drive the vehicle for 20 minutes to stabilise engine operation and temperature.
Connect the SDS and conduct 3 stall tests allowing 2 minutes at engine idle between each test to reduce ATF
temperature.
View the SDS knock correction data in relation to the table below;

Maximum Knock Correction Stall speed if AT Comment
Up to –4 Degrees Up to 2400 RPM Engine is performing normally
-9 and greater (-10, -11, etc) 1900RPM and less Report via FPRS to Subaru (Aust.)Technical Dept.

4. D4AT shift regime in the 2.0r Impreza and 2.0R Liberty the D4AT has 3 modes as follows;

a. Normal mode
Normal Mode allows maximum fuel economy to be achieved if the driver so desires. The AT is the least responsive in this mode up changing and down changing to minimise engine speed and hence reduce fuel consumption.

b. Sport Mode
Sport Mode increases the responsiveness of the AT to throttle movement up changing at higher engine RPM and down changing more readily for a given throttle opening in comparison to normal mode. Fuel economy is a reduced priority as the AT compromise has been shifted towards increased responsiveness and performance.

c. Manual Mode
Manual Mode allows the driver to direct gear position and shift point for maximum performance, responsiveness and driveability. The compromise is now about performance only and fuel consumption is not an issue.

Therefore if the customer concern is sluggish performance in a 2.0R Impreza or 2.0R Liberty with AT and the vehicle is performing as the manufacturer intended the customer can improve the responsiveness of the vehicle ( and hence “perceived “ performance ) by using sport rather then normal mode.

As an example when entering a roundabout at slow speed the AT will select 2nd gear. As you open the throttle to accelerate out of the roundabout in NORMAL mode the AT will attempt to maintain 2nd gear in the interests of fuel economy. If SPORT mode is selected the AT becomes more throttle responsive and may select 1st gear to exit the roundabout with improved acceleration.
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Re: Weird Acceleration

Postby mihai » Thu Aug 06, 2009 10:39 am

thanks for the reply,

not sure if that helps. I dont have a SDS module to connect to, and even if i did, i wouldnt know how to interpret the data. Also, the modes are largely related to the AT not the MT. My car has always been serviced by Subaru, so i highly doubt that the wrong oil has been used, and i always use Shell Vpower, which at 98 octane is above the recommended 95 Octane.
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Re: Weird Acceleration

Postby adz2.0r » Thu Aug 06, 2009 5:25 pm

thanks for that sheppo9.

$100 to diagnose the problem :angry2: that cant be right can it, they will probably just throw on the sds module and see whats going on.
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Re: Weird Acceleration

Postby yumcha » Mon Aug 10, 2009 10:50 pm

its probably bad fuel
i used to pour @ my local station and get the same symptoms now and then
never been back there for about a year
and up til now never had the problem again.
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Re: Weird Acceleration

Postby mihai » Tue Aug 11, 2009 1:40 pm

Thanks for the reply,

My tank is running pretty empty, might try BP Ultimate or Mobil 8000. See if theres a difference from Shell Vpower
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Re: Weird Acceleration

Postby yumcha » Tue Aug 11, 2009 7:40 pm

pour a new tank of quality fuel
give it a couple days n you should be fine
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Re: Weird Acceleration

Postby mihai » Tue Aug 11, 2009 10:07 pm

got a new tank of BP Ultimate, seems to be running better already. It was weird coz up until today i only ran it on Shell Vpower, from the same servo, and it only occasionally did what was said above.

we'll see how the BP Ultimate goes, if no problems, will stick to it.
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Re: Weird Acceleration

Postby AndySTi » Tue Sep 01, 2009 12:44 am

wassell2381 wrote:is the car an auto?
coz if it is then the car hates it when its in a high gear doing low revs and then when depressing the accelerator they have a delayed response before changing down which gives the car more acceleration. That's all i can think of that happens with my 2.5 auto

Spot on! When i first started driving the lib i noticed that, but after a while i kind of got used to the delayed response and dodgy shifts. Doesn't pull like a turbo but still an enjoyable car to drive.
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