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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
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16,174 Posts
Discussion Starter #1
My 2006 Outback XT 5AT has a (normal temp) idle of 750 rpm. When placed in gear(D) or (R) the rpm imediately drops to around 500 and the motor/tranny will start to shake. When the car is cold and the rpms are much higher and this vibration isn't felt. As soon as the idle speed starts to drop. The above senario occurs.

The shudder is stronger and the idle is a bit lower (400-300 rpm) as the car rises to normal operating temp. Oddly the situation can be made slightly worse by activating the rear defroster (heavy electrical load)

Otherwise the car runs fantasic. Strong, smooth, turbo power delivery.

I have already verified that the front axles have been replaced. Both axles were done at a Subi dealer with Subi-Reman sourced axles.

Any ideas...Help
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
Joined
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16,174 Posts
Discussion Starter #2
Some additional info gathered today. The defroster issue got me thinking.

Battery voltage before starting 13.4
Voltage when started cold 14.6/14.5

With car warming and warm voltage 14.4/14.3

Dropping the car into gear will drop voltage to 13.8 for a moment then it will recover to 14.2/2 motor is now shuddering.

Turning on lights, rear defroster, climate fan to max will cause voltage to drop to 13.8-14.0 shuddering and idle experience is slightly worse.
 

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Premium Member
01 VDC, 05 R Sedan, 06 BAJA EJ257
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15,103 Posts
Check the amperage output of the battery and replace if lower than 450 amps. Check the ground cables and correct any corrosion issue.
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
Joined
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16,174 Posts
Discussion Starter #4
Good battery, still low idle

Thanks for responding.

The battery is good. I recently replaced a weak battery with the current one. I had the new one and the charging system checked just in case. The alt is putting out 109amps when in gear, with the above accessories on. It is just stock output, would a higher output battery help?

The main trouble really seems to be idle drop/speed. When placed in gear, the rpms drop and don't recover. In fact, the idle will continue to drop slightly with if stuck in traffic or in line at the ATM.

I recently changed the air filter and the plugs...no effect on this condition.

Here is the whole story. I purchased the vehicle 3 mos ago with 66,000 miles. I bought it from a Nissan Dealer. They took it on a trade, it had a "motor issue". Bad turbo, bango filter failure, big surprise. Prior to my purchase, the Nissan dealer replaced the turbo. I bought the car, it had a warenty on the work, it ran great(at test drive). It did idle low at test drive, I pointed it out and the, salesman said they noticed it too, they would send it to thier Subi affiate because they could do anything with it.

I drove the car for about 500 miles and BINGO...failure. All said and done, I got a new turbo, short block, heads, some new valves, springs, etc all courtesy of Subi. All of this above work was done at a Subi dealer.

The dealer that did the above motor work told me the idle/vibration were "normal".

Since, the car has run beautifully outside of this idle issue. I find myself bumping it into neutral because it is so annoying.

I did notice a CV vibration at speed. I had another dealer diagnose that a poor quality CV shaft was installed on the passenger side. They recommended a reman axle through them and they also verifed the driver side (replaced at 60,000 along with lower control arm bushings) was A Subi part. I replaced the passenger side as per their recommendation. No change to the above symptoms.

This dealer also felt the idle/vibration were normal. All I know, if this were a 5MT I would not be having any issue. Because in N or P it is fine. I can even heal-toe the throtle when stopped and pretty much correct it.

I have basically ruled out bad axles but who knows. Is there a real test for play or movement etc. I haven't gone crazy over motor mounts, suspension bushing yet. It's cold here, besides I don't see any other symtoms in these areas.

I haven't owned a Subaru since my 1995 Legacy. Great Car. And I owned many of the Loyal cousins. Even and '87 XT Sedan w/ the AIR pillows and H/L range. That was a tough POS.

Since, have been building and driving solid axle, 4wd offroad vehicles. I moved from the mountains to Denver, and the lifted Cherokee (which was the small rig) is just not city practical.

Hence, the XT. Fast, Fun, great build platform. However, I want to solve this idle issue before I start spending cash on a build. Like I said, I have building much different rigs.

Anymore input would be great
 

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Premium Member
01 VDC, 05 R Sedan, 06 BAJA EJ257
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15,103 Posts
How much carbon is on the throttle body? I know you've had a lot of repairs, but its possible that even with the intake assembly removed from the car making it easy to clean, it may have identical carbon build up of an engine with 67k miles.
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
Joined
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16,174 Posts
Discussion Starter #6
YEAH...good point. One would expect that any decent mechanic wouldn't be putting dirty parts onto a shiny clean motor but who knows.

Looks like it is under the intercooler...looks like a pain...looks like it is time to get a manual and get commited.

Think the SeaFoam route is one to take? I guess I'll eyeball it first and go from there
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
Joined
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16,174 Posts
Discussion Starter #8
Well,

The throttle body looked real clean from the intake side.

I did the SeaFoam liquid treatment directly into the throttle body. I sprayed cleaner as well at least on the intake side. I did not remove the throttle body and clean the engine side. Was this a mistake?

I did find some oil residue in the intercooler, likely from the turbo failure. I cleaned the intercooler real well.

I drove at least 10 miles or so. After the smoke quit I got into the turbo a good bit.

My initial impression is zero change. I took the intercooler off again and inspected it. Clean inside, the intake tube and throttle body were clean.

I used some more of the spray. Tried to soak best I could without it stalling. I'll see if there is any change.
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
Joined
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16,174 Posts
Discussion Starter #10
Any specific target areas? I don't have a vac gauge. I know I have heard about some red-neck procedures.

I know the motor rpm drops like 250-300rpm when put in gear and doesn't ever recover to 700+ like it should be. I swear in dirve-thru's, I feel like I can hear a hiss when dropped into D from N. Tough to tell since the load on the motor changes.

You have a similar vehicle (save the Mods). Where does yours idle at? In D the shaking starts when the needle is just a hair above the lowest line, (at the bottom) below 1000rpm. When in N it is closer to the top third near 1000rpm.
 

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18,545 Posts
Not an XT, but when the engine and transmission are fully warmed up, my 07 idles in P or N at around 700 rpm, and drops to around 615 in R or D.

The tachometer on my car isn't sufficiently marked at the low end; my readings are from a scanner (Romraider Logger) connected to the OBD connector -- this is the data the ECM is using. (The numbers cited above are common/averages; sometimes the hot idle in gear seems lower, but I don't have the scanner on at those times to verify exactly where it is.)

So, your drop does appear relatively high, but comparison with XTs of the same year might be more conclusive due to possible differences in engine control software in different years and engine formats.

I wonder if scanning of engine parameters (injector pulse width, manifold pressures, throttle voltage and position, etc) might reveal a possible cause.
 

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Lawn ornament XT
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14,356 Posts
The idle drops on my XT in gear as well... just not enough to shake me. Once in a blue moon it has let the idle momentarily collapse, resulting in an unwelcome shudder. I haven't bothered to chase it down.
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
Joined
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16,174 Posts
Discussion Starter #13
Is there a scanning tool usefull enough I can buy or is this something best done at a shop/dealer?

I don't mind an investment if it is really useful.
 

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18,545 Posts
FreeSSM and Romraider are two free scanner-type programs that should work with your car. They are discussed, and demonstrated in http://www.subaruoutback.org/forums...426-freessm-complete-access-your-ecm-tcu.html.

As noted, both require an interface cable, but these are inexpensive and available from sources on ebay. FreeSSM will read and clear trouble codes, and display engine and transmission parameters (sensor data etc). Romraider Logger does not read codes, but can display engine and tranny parameters in various formats (text, analog gauges, digital gauges, graphs) and record the data in a spreadsheet file for subsequent analysis etc.
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
Joined
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16,174 Posts
Discussion Starter #15
Scanning Link

Thanks OM,

I looked at the link you provided. So it looks like there is some ECU MODs I can do with this software as well, same as chips?. I was planning on building this car up bit. I"ll check all of this out and see where things are at anfd go from there
 

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2003 LL Bean Outback H6 and 2019 Outback Base
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514 Posts
My LL Bean H6 is doing the same thing..... When warmed up.....in Drive...it idles at 350..... in park 450.......It is VERY annoying...but other than that....car runs great....Cardoc has mentioned maybe te MAP sensor...It regulates the air intake to the vehicle..............Of course its not enough that it also has an IAC valve AND throttle sensor......................OVER engineered.............I replaced all but the MAP sensor.....waiting until weather gets better......its annoying....but not threatining.....
VERY interested in your outcome..PLEASE keep me posted....if could send to me direct...much appreciated.....if I resolve I let you know as well
 

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106 Posts
Has anyone checked their motor and/or trans mounts?

The idle may be normal, the gauge could be reading a little off but the vibrations could be due to bad mounts.

Has there been exhaust work done on any of these vibrating vehicles?

Sometimes a shop will not do a real good job at isolating the exhaust and the pulses may exaggerate the vibrations.

I am not sure if all Subarus are unibody, but with no frame, everything is pretty much attached right to your butt.
 

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Lawn ornament XT
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14,356 Posts
Thanks OM,

I looked at the link you provided. So it looks like there is some ECU MODs I can do with this software as well, same as chips?. I was planning on building this car up bit. I"ll check all of this out and see where things are at anfd go from there
One of the mods you can do is artificially raise your idle setpoint. It's just a few clicks away.

Now, you could be masking other symptoms... with great power comes great responsibility.
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
Joined
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16,174 Posts
Discussion Starter #19
Not an XT, but when the engine and transmission are fully warmed up, my 07 idles in P or N at around 700 rpm, and drops to around 615 in R or D.

The tachometer on my car isn't sufficiently marked at the low end; my readings are from a scanner (Romraider Logger) connected to the OBD connector -- this is the data the ECM is using. (The numbers cited above are common/averages; sometimes the hot idle in gear seems lower, but I don't have the scanner on at those times to verify exactly where it is.)

So, your drop does appear relatively high, but comparison with XTs of the same year might be more conclusive due to possible differences in engine control software in different years and engine formats.

I wonder if scanning of engine parameters (injector pulse width, manifold pressures, throttle voltage and position, etc) might reveal a possible cause.
So, I finally got my VAG COM cable and the the scanner. It connects and works fine.

Now how do I use this data. I only played with it for 15 min or so. My main question. Where do I get the comparative data so I know the acceptable ranges or the testing blocks?

I have no codes. The dealer has told me that if any of these blocks are out of spec. then the code will pop.

Can the data during the test be saved? I guess screen shots?

My initial idle readings are not as low as I thought. I didn't get the car completely warm but... 780rpm (N)....580rpm (D). I wasn't really able to determin the rpm at which the motor starts to shake. I will build some more tests. Try to get some screen shots.

Any suggestions on specific testing blocks or testing for engine/tranny that I should be targeting? Can any specifically help diagnose vac. issues?

I welcome any suggestions.:confused:
 

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18,545 Posts
If you're using FreeSSM then there's no way to save the data other than screen shots. This is where Romraider Logger really has the advantage. It not only can save data but do so for all the selected parameters over a period of time (test/record period). This way, the data can be analyzed "off-line" afterwards, and all the relevant parameters examined at the point when the symptom, such as a notable drop in rpm, appears.

I don't think there's a comprehensive list of whats "normal". The FSM has a chart of the available parameters, and typical readings for some at idle, but I've noticed that even with my 07, there are differences.

I don't have an 06 FSM, but the relevant pages are found in the H4DOTC (turbo) Engine section, Engine (Diagnostics) sub-section, Subaru Select Monitor sub-sub section, under the chart entitled READ CURRENT DATA FOR ENGINE. (NORMAL MODE).

This post (http://www.subaruoutback.org/forums...omplete-access-your-ecm-tcu-3.html#post370942) has the engine parameters chart posted by ntippet, but I'm not sure which engine it applies to. (The parameters that are listed, and those actually available on your car could vary due to production changes. Also, the "Display" title indicated in the chart, and how FreeSSM or Romraider identifies a particular data stream could be different. But all the available data will usually show up in one form or another in both programs.)

I would probably start by logging most of the available engine parameters. (The "switch" parameters -- those that are just on or off -- are probably not needed.) Some parameters can be eliminated early, such as fuel temperature (unless it changes suddenly at the same time as the rough idle, which is not likely), and vehicle speed (car's not moving), but others you might want to have a look at to see if they change when the idle drops, and then decide whether these could be cause or effect, and if the latter, they too can be disregarded in subsequent logging sessions.
 
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