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Discussion Starter #1
Hey everyone so I have a problem that has me stumped. My Outback has issue at about 3000 rpm, It starts bucking usually just in 3rd gear (MT) when I let my foot off the gas and going down a hill is when its very noticeable. When it starts to buck the RPM fluctuates as well. The fluctuation is very small maybe as much as 500 rpm. This problem usually goes away once the vehicle is warmed up. Only first few mins of driving. There is no check engine light. The clutch is in good condition and doesn't slip at all. So far I have changed spark plugs but that didn't help. Wires are good too. Anyone else experience this? Im thinking it is fuel related because fuel is generally thicker when cold. I don't think its a transmission problem either because it shifts good and once warm it preforms great. Any help would be GREAT THANKS!
 

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2004 Outback Wagon EJ259 - 4EAT
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Strange, i've noticed something very similar in my 2004 OBW...mine has a 4EAT though. I always attributed it to the temperature of the ATF...but your experience seems to negate that theory.
 

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Yeah its weird I can only get it to do it when its cold. Usually only happens going down hill. I guess it is temp related but this one has me stumped...
 

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I've got a similar thing in my '09, only it happens in more conditions than just downhill and not just when cold. I am suspecting either motor mounts or something more sinister and driveline related, but I won't be able to do much diagnostics til next weekend. I will post my findings, if any, and hopefully that may help...
 

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2001 VDC/SC One of a Kind
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How many miles on the car? Its a pertinent question.


Does it do it every day? Or, is it occasional?


Is it really only when the engine/trans are cold, or you just haven't noticed it later on? Can you make it do it on the same hill after driving a while?


Is it really hill related only, or can it be done on a flat road? A hill increases the load on the drivetrain and will magnify an issue, so if it does it on a flat road, and its noticeable, it would make a difference.


Olds, Radio Head, Same questions, plus: Does yours do it off the throttle also? Or does yours do it on the throttle?


Post back with the answers and we can go from there. :)



.
 

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Discussion Starter #7
Hey car has about 160k miles. It does it on occasion I guess mostly when I coast so I guess it could be on a flat surface. But this is only when the car is bone cold like the first 5-10 min of driving. Once the car heats up I never notice this. Also if this helps when I first start the car first thing in the morning when I go to start it there is like a 1-2 second pause when the key hits the start position to when the car actually starts. I changed my terminals on battery and helped a little. But this also goes away when I drive it. Don't know these are connected in any way. Has me stumped.
 

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2001 VDC/SC One of a Kind
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Check the amperage output of the battery, then check the alternator output. Also, what condition is your alternator belt in?

You may also want to check that there isn't any corrosion on the battery cables and also the ground lugs on the intake, fender, firewall and block. The larger of the grounds is on the block by the starter.
 

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2004 Outback Wagon EJ259 - 4EAT
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It does it off the throttle. Feels like the car is plugging (not sure if that analogy will make any sense though...) Just like the OP, it goes away after a short while.
 

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Discussion Starter #10
My battery is brand new just bought it a months ago. And as of last night new and good battery connections. All the belts look to be in good condition (no cracking or fraying) I saw the ground on the block it looked like there was old grease covering it. And the one on the fire wall looked to have a little green corrosion on it.
 

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Ok so I just cleaned all the grounds firewall and block and really didn't make a difference. Still has a 2 sec start delay and this time got it to buck on flat ground and not on a hill. Again this only does this when bone cold once car has been running for over 2-3 mins it goes away. This is really not making sense.
 

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Ok so I just cleaned all the grounds firewall and block and really didn't make a difference. Still has a 2 sec start delay and this time got it to buck on flat ground and not on a hill. Again this only does this when bone cold once car has been running for over 2-3 mins it goes away. This is really not making sense.
A few more things to check on.

Fuel filter.

If you can get your hands on a fuel pressure gauge, check the fuel pressure at the filter hoses. You can get a cheapo gauge at the parts store that will have adapters that allow you to tie in line at the lines. Just bypass the filter and connect it there.

Clean the throttle body. Use a good solvent and a soft bristle brush to remove the carbon. Carbon build up will effect the tps feedback in relation to the actual position of the plate.

There is a ground lug on the intake manifold that is in circuit with the tps, map, af and iac.

Did you check the amperage output of the battery, or just for 12V? Did you check the alternator output with a load?

Check your transmission mount.

The fuel trim runs at open loop during a warm up and switches to a closed loop after learning and operating temperature is obtained. This relates to the engine operating in a manner that torque output is actually a bit higher at cold engine temperature over hotter. So, when cold, any issue most times will make itself apparent. Also fuel delivery needs to be close to peak to supply the fuel needed to warm the car up. Sensor output necessary for the ECM to correct itself is also important.

There are a few possibilities for correction and narrowing the problem down. Start with this and see what comes of it. The objective to is find the cause before throwing parts at it.
 

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Discussion Starter #13
Hey I will definitely check the fuel filter. That is a good possibility because any restrictions during warm up can cause issues. Where is the fuel filter located? I thought outbacks had filter under hood by fuel lines.. I took off the whole air cleaner saw the throttle body was a little dirty not too bad was going to clean but didn't have any fuel/carb cleaner. is the ground for the tps is located on the intake manifold where? Thanks for all your help
 

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2001 VDC/SC One of a Kind
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My bad. Filter is in the tank if its not on the fender by the master cylinder. California Emission standard update for the 04 models in all manufacturers. You may have a late build.

The ground lug will be on the intake manifold rearward. Follow your harness and anywhere you see a black wire coming out of it, follow to where it connects to a lug bolted to the engine or body.

Fuel pressure should be 30-35 idling and spike to 40-45 with the pressure regulator vacuum hose disconnected.
 
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