poor acceleration

[alpop]

"Should look the same as the plug at the sensor end of the harness."

 

Don't know what you mean by this - There is the O2 sensor with wires coming out of it, no plug, then the wires go back and dissappear above the transmission.

 

Is the plug which I need to disconnect visible from the (driver side) engine compartment or from underneath the car?

[alpop]

 

This thread is long and unwieldy, here is a summary of my
lack of success - any ideas are appreciated!

 

THE CAR:  1999 Legacy
wagon 2.2L automatic, very nice inside and out.

 

THE HISTORY:  PO removed the oil drain plug and purposely burned up the
engine.  A replacement engine (same
vintage 2.2 phase II) was dropped in with about 140K miles on it.

 

THE PROBLEM:  very
sluggish to (sometimes) non-existent acceleration below 2500 RPM under load (fine
above 2500 RPM - this switch spot can vary, it surges as it switches from poor
to normal acceleration), intermittent problem, but for example has been doing
it constantly the last two days (and it has been rainy).

 

WHAT WE KNOW/DIAGNOSIS: 
If one disconnects the battery and resets the ECU it drives beautifully
for 15-20 minutes then starts to malfunction (did at least 3 times) - I assume
that for these 15-20 min. it is on default settings and then the ECU changes
things and it runs poorly.  Thus it
"may" be either a bad sensor feeding bad info to ECU or a faulty
ECU.  IS THIS A VALID CONCLUSION?

 

Throws no codes unless I mess with the sensor (unplug, check
voltage etc).

 

THINGS CHANGED REGARDLESS OF ABOVE DIAGNOSIS:
 

-Spark plugs checked, new and gapped correctly

-new ignition wires installed

-new PCV valve installed

-new air cleaner element installed

-checked for vacuum leaks (fine water spray, engine running)

-checked coil pack for leaks (fine water spray in dark,
engine running

-checked all engine harness plugs and other - secure

 

THINGS CHECKED ASSUMING ABOVE DIAGNOSIS: sensors checked
either by, 1. replacement, 2. voltage input and output. or 3. disconnecting and
see if runs better.

 

MAF sensor (cleaned, unplugged didn't run), TPS (voltage ok
and replaced temporarily-no change), Knock sensor (replaced twice-no change),
Pressure sensor (voltage ok and unplugged ran the same), coolant Temp sensor (replaced
- no change), front O2 sensor (unplugged it ran the same)

 

Rear O2 sensor, cam sensor and crank sensor not checked,
assume it wouldn't run w/out the latter two.

 

ANY MORE IDEAS?  Any
more sensors to check?

 

Are there (non-engine) things that one might expect burning
up the engine would damage?  The end of
the tail pipe is very black, but it doesn't use oil w/new engine.

 

Should I take it somewhere for a professional diagnosis or
try a $50 salvage yard ECU, or a $250 rebuilt ECU?

 

 

[1 Lucky Texan]

it would be very nice to see live data. Or, if you have or can get scanner, create a CEL and get freezeframe data.

 

did all 4 sparkplugs look the same?

 

does the car get reasonable mileage?

 

could you drive with a vacuum gauge attached and take readings when the car exhibits its failure 'mode'?

Edited March 27, 2015 by 1 Lucky Texan

[Fairtax4me]

There's a plug. The sensor harness runs about 12" or so and there's a plug just above the trans crossmember.

[xdeadeye1]

Throwing out ideas.. (im not a mechanic)

 

What if the Over drive is kicking in when it shouldn't be.

 

It wouldn't have good power.

[alpop]

Now there's a completely new idea - let me give that some thought!

 

 I am also thinking of putting in the FWD fuse and seeing if that makes a difference.  You probably could simulate the problem by artful manipulation of the parking brake -

[powderhound]

I'm having the same issue with a 98 Legacy that I just bought.  My 95 Legacy that I totaled in Nov had the same issue as well.  It seems completely random and will come and go in the same trip.  Being a manual I just live with it and keep it above 2500rpm.  The 98 only just started doing it though I've only owned it for ~1500 miles.  It started after I changed the oil and installed a tach.  Probably coincidence and unrelated.  The 98 has a cel p0440 for something evap related.  I think this may be the issue.  My 95 was throwing no codes but was having evap issues like no pressure released when undoing the gas cap.  Maybe have the evap system smoke tested?  I'm just gonna live with mine as this is a 800$ throwaway vehicle that I have no interest in spending money on.

[sirtokesalot]

mine acts like this when its first warming up for the day after its been run for 10 to 15 min it gets better but can be noticed sometimes.

[alpop]

Thanks for the input guys-

 

Rear O2 sensor:    This is the second time I crawled under the car and couldnt find it, must be between the transmission and floor boards, enough of that, doesn't seem likely it would cause the symptoms anyways.

 

Overdrive:  Don't know much about it, is it a three speed automatic with electronic overdrive?  when its dogging it and I push the accelerator down further, it might start around 1500 RPM (30 mph) and then sometimes seem to first shift down just a little at first (maybe to 2000 RPM) but seemingly not a full gear - maybe its shifting out of overdrive?  Is the engine really supposed to be at 1500 RPM at 30 mph?

 

If its electronic overdrive there should be a wire or plug I could pull to see if the problem goes away

 

Evap system:  No code but I did remove the gas cap and there was NO pressure release, come to think about it I think that has always been the case when I put gas into it, I seem to have thought something was different but couldn't put my finger on it.  Cap gasket looks fine.  Would this really cause these symptoms?

 

I've been telling myself its not a transmission problem but having exhausted most other possibilities maybe I should re-consider?  Not typical transmission symptoms.  I Still need to reconcile with the "drives perfect for 20 minutes after resetting the ECU",

 

Is there a separate Transmission Control Unit?

[robm]

If you unplugged the front O2 sensor, and it ran the same, then that sounds to me like the problem? 

[alpop]

it would be very nice to see live data. Or, if you have or can get scanner, create a CEL and get freezeframe data.

 

Beyond me, thus the professional diagnosis idea

 

did all 4 sparkplugs look the same?

Yes

 

does the car get reasonable mileage?

No, haven't checked exactly but probably 15-20 mixed driving, not suprising the way it runs

 

could you drive with a vacuum gauge attached and take readings when the car exhibits its failure 'mode'?

Again, professional diagnosis

[alpop]

I'm on to thinking about the transmission now, there are a few quirks I've been ignoring

 

When it seems to be acting pretty normal (no major heasitation below 2500 rpm) it still "sometimes" does the following:

 

1.  Doesn't want to shift from 2nd to 3rd (or maybe its 3rd to 4th)

2.  At higher speeds when you take your foot off the accelerator its like an engine brake is applied, although I don't notice a corresponding increase in rpms like it has shifted down.

3.  No way to tell what gear its in except when its light, looking down at the shifter (a problem in the dark).  I saw a pic of my dash board and it seemed to show there is a gear indicator located vertically beneath the vehicle/open door icon (which works) on the dash.  No sign of the gear indicator on my dash.

 

I 've done a little digging around, and there should be a Transmission Control Unit usually above the brake pedal, independent of the ECU.  The TCU reacts to a number of sensors, some different than the ones I've tested.

 

I need to find this and check it out - wonder if it is completely independent of the ECU or if it works throught the ECU?

[alpop]

Turns out this 4EAT transmission is a 4 speed, no electronic overdrive, 4th is just referred to as the OD by virtue of its gear ratio.

 

Here is a great write-up on the transmission:

 

http://www.subaru-svx.net/photos/files/ZMan/13060.pdf

[1 Lucky Texan]

it would be very nice to see live data. Or, if you have or can get scanner, create a CEL and get freezeframe data.

 

Beyond me, thus the professional diagnosis idea

 

 

did all 4 sparkplugs look the same?

Yes

 

 

does the car get reasonable mileage?

No, haven't checked exactly but probably 15-20 mixed driving, not suprising the way it runs

 

 

 

could you drive with a vacuum gauge attached and take readings when the car exhibits its failure 'mode'?

Again, professional diagnosis

A vacuum gauge is very inexpensive and there are guides online to help with interpreting the readings. You may be able to borrow one from a parts store. Posting live or freezeframe data here will get you some good analysis but, I suspect finding a good local shop is gonna be more likely to pay off for you in the long run.

[alpop]

Hmm, well maybe it is time to get a vacuum gauge.

[1 Lucky Texan]

ask the parts store what they loan out. You'd be surprised. I borrowed a vacuum pump to recharge my a/c . You have to 'buy' the item, but they credit your card back when you return it.

probably can borrow a vacuum gauge. Might need to buy a plastic T and some hose though.

 

might help determine a sticking valve or clogged exhaust.

 

 

 

Edited March 31, 2015 by 1 Lucky Texan

[alpop]

1 lucky tex, thanks for the info - I will do that on the wkend probably-

 

I did find the TCU right above the brake pedal as supposed to be, all plugged in and such - no obvious problems

 

As I mentioned, there is absolutely no readout for gearshift position anywhere on the dash, and the area beneath the car/door open icon doesn't appear to be an active part of the multimeter.  Owners manual has no reference to a shift position readout.  The shifter console is not lighted (couldn't find a burned out bulb under there) so there is currently no way to know the gearshift position in the dark!

 

I really can't believe they designed the car this way!  Did they?

 

Also noticed two non-mated dissimilar plugs under the dash to the right of the steering wheel, no where to plug them in, probably for some options the car doesn't have?  Although they each have about a dozen connections, so probably not just for dash switches. These are near the smaller green check male and female plugs.

[Fairtax4me]

There is supposed to be a light in the console. They burn out all the time.

 

Plugs under the dash, a black 6 pin and a yellow 9 pin are diagnostic plugs. The yellow is Subaru SSM and the black is test plug for the TCU Airbag and ABS modules. Grounding certain pins in that plug causes the corresponding module to blink any diagnostic codes it may have stored.

 

 

It doesn't sound like you have a trans problem. The trans may be seeing more input from the throttle position sensor and holding gears longer because that's the way it's programmed. More throttle = higher shift points.

 

There is a lot of drag in the AWD drivetrain and these tend to engine brake pretty well on the highway, especially if you're running in the 3,000 rpm range.

[alpop]

All good info, thanks Fairtax-

[xdeadeye1]

Turns out this 4EAT transmission is a 4 speed, no electronic overdrive, 4th is just referred to as the OD by virtue of its gear ratio.

 

Here is a great write-up on the transmission:

 

http://www.subaru-svx.net/photos/files/ZMan/13060.pdf

Im thinking your issues lie in one of these inputs:

but again,, I really don't know the answer.

 

TCU Inputs

• Throttle sensor/idle switch

• Vehicle speed sensor #1

• Vehicle speed sensor #2

• Tachometer signal

• Inhibitor switch

• Cruise control signal

• ATF temperature sensor

• Ignition/battery voltage

• 1-HOLD switch (if so equipped)

• Forced FWD

TCU Location

MPT Assembly MPT Clutch MPT Clutch Hub Reduction Shaft Seals MPT Power Flow

11

[alpop]

well now I'm thinking I can buy a vaccuum/fuel pressure gauge for $25 and a OBDII scanner all for less than the probable $100 diagnostic charge.  With 4 cars they should come in handy again (right, my daily transport is a bike - go figure).

 

I see the "Autel MS509" OBDII scanner on Amazon for $44, and it seems to just about do it all, livestream ECU info, freeze frame data (what's this?) etc., in addition to reading and clearing codes.

 

Seems like an amazing price, several reviews from mechanics are very favorable, though it sounds like its older and no longer supported by the company - thus the reduced price.  Maybe you wouldn't be able to update it but hey my newest car is 2006 anyways.  Anybody know anything about it?

[Fairtax4me]

Sounds like a good deal for a plug-in scanner that will read live data. At this point we do kind of need to see what the computer thinks is happening. 

 

Freeze frame is a set of data that is stored when a code is set. The ECU records things like engine speed, temperature, vehicle speed, fuel trims, and some other things that can be useful for diagnosing intermittent issues. Freeze frames are only stored if a code is set. 

 

I do think its a good idea to invest in a code reader or scanner or some kind. If you have a smart phone there are even less expensive options that can be made to work with the Torque App, and the use of a Bluetooth OBD2 interface/adapter. There are also plenty of programs available for computers that can use the same bluetooth or a USB connection. Rom Raider is one of them, but I'm not sure if that will work with the 99. Evoscan is popular and runs about $75 for the program and the adapter sold by Evoscan. You can also make your own or order one premade for a bit less. 

[alpop]

Manifold vacuum test result:  test elevation = 2560 ft.

 

 

Idle in Park: engine cold, high idle steady at 18, slowly climbs to 20-21 as engine warms and goes to low idle.

 

Blip throttle:  shoots down to 2 then quickly rebounds to 22-23 (not 25) then settles back at 20-21

 

 

Drive test:  when accelerating at lower RPM and its dogging, vacuum at 0-1, when rpm finally passes 2500 and acceleration becomes normal, climbs to 2-3

 

The gauge I got also can test fuel pressure I guess, but gasoline is a whole other thing and although the Haynes manual details the procedure it seems like they have left out a few steps.

[alpop]

one more vacuum test.

 

At idle in park at steady 21, slowly increase rpm to 2500 and hold, steady at 20.

[Fairtax4me]

Vacuum gauges can be used for fuel pressure testing on old cars with carburetors. The guage probably only goes to 15-20 psi. Typical fuel pressure for a carbureted engine is 5-10 psi.

Your car runs about 35-45 psi depending on engine load. Far too high for that style of guage to handle.