PDA

View Full Version : throttle issues?


joshuah
10th November 2009, 06:38 AM
Hi,
I'm going spare trying to diagnose this one!
Problem is with my MY02 Outback. The accelerator is very touchy. Releasing it just a fraction and the car loses all momentum, lunging me forward. Deperessing it again ever so slightly and she re-engages and takes up the slack quickly. There is no in between and reducing to a coast can not be done smoothly; in fact, it won't coast smoothly at low speeds, not even on cruise control.
When descending down hills in any lowish gear, just engine braking, she can buck and hobby-horse. Depressing clutch stops this...until the next time.

I have read that it may be an ECU problem, or engine/tranny mounts, Throttle sensor, anti-knock sensor... but no-one seems to know. Mounts seem ok, very little backlash in drivetrain.

I have already installed a 2nd clutch, which did nothing except cost me lots of $. The mechanics aren't too sure either, so I'm releuctant to spend more on it for no gain! Scanner indicate nil error codes.

Anyone else have such problems? How should I tackle it?

Beigewagon
15th November 2009, 08:06 AM
joshuah,

not sure if it is the way the computer is set for the fuel injection, or what, but our '05 Impreza does the same.

Beigewagon.

Kevin
16th November 2009, 03:09 AM
Sounds electronic - perhaps throttle control / idle control valves. Have a search over on subaruforester.org and ozfoz.

Engine does not return to idle.
1) Idle air control solenoid valve
2) Engine coolant temperature sensor
3) Accelerator cable (*6)
4) Throttle position sensor
5) Pressure sensor
6) Intake air temperature sensor

chickenlover
16th November 2009, 04:36 AM
sounds like an exagerated effect of the normal ecu operation - try reflashing the ecu (disconnect it over night)...

nipper
16th November 2009, 08:48 PM
Vacume leak?

How many miles on this engine. When was the last time it had a tuneup?

nipper

joshuah
17th November 2009, 12:33 AM
Hi,

She's got 175000km behind her. I do all usual servicing except timing belt, but a couple weeks ago, the mechanic cleaned the throttle body, which was apparently a bit grubby. It drives nicer but the problem remained.

Problems seemed to coincide with the installation of a new clutch to a single solid/rigid flywheel. The first one installed was a 'clutch pro' brand. Mechanics thought the spring was a bit weak, so they suggested installing an Excedy, which they did, but did not fix the problem. It's a better clutch and has a nicer feel, but that's it. Related?

I also read somewhere that Foresters had a similar problem in Canada and US which was fixed with a software upgrade. Is this likely in Oz? Are there bulletins of updates available online or similar?

Meanwhile, I have really adapted my driving style which has helped, but not in low gears. babying the accelerator and releasing it ever so slowly works a bit. Hopefully it'll reduce the wear drivtrain for a long as possible.

thanks for the input.

joshuah
17th November 2009, 12:36 AM
oh, and tried the ECU reset, installing a new stereo. Disconnected for a couple hours. Also put in a new battery to fix hard cold starting. This didn't work either. I think I need a new mechanic?

chickenlover
17th November 2009, 01:25 AM
well if it coincided with the clutch /flywheel - I wonder if the flywheel is the culprit!? is it idling lower than before?

joshuah
17th November 2009, 05:49 AM
It's a new flywheel and they re-machined it before putting the Excedy in. The flywheel has done about 5000km all up.

It may actually be idling a little lower, around 600-700rpm. What does that tell you?

chickenlover
17th November 2009, 06:01 AM
Im no mechanic but im thinking if its idling lower, and dropping revs quickly when off the gas, maybe their is some sort of friction against the flywheel (throwout bearing, clutch??) Not sure... maybe 'Rally' on here can chime in with some advice :)

Gremlins
23rd November 2009, 11:31 PM
I have an 06 Impreza that does similar also. There's a slight downhill stretch of road that I drive down everyday and it's impossible to keep a constant 60km/h (the speed limit) on this road. Throttle off and the car slows down, open the throttle the slightest amount and it starts picking up speed. It must really annoy drivers behind me!!

I'm thinking it has something to do with the interaction between the idle air control valve and injector cut. When the car is rolling the idle speed on mine always is above 1000rpm (coasting clutch in or neutral) it only seems to drop down below this if you actually stop (ie. no reading on vehicle speed sensor). Couple this with what I suspect is the ecu cutting the injectors at throttle off and your high idle suddenly gets cut as the fuel stops being injected, then the slightest touch of the peddle turns the injectors back on and the vehicle then takes off again on a high idle speed.

Anyway that's my theory on it and it's only a theory as such and still doesn't help that the car can be a PITA to drive in certain situations. The amusing thing for me though is the fact that my previous L-Series with multipoint EFI EA82T was much better behaved - and that was without the benefit of the subsequent 20 years of EFI development - lol.

Rally
28th November 2009, 09:38 PM
Brain's a bit asleep after a night out, but have you checked the throttle cable is right? I had a scary moment once in my WRX when I floored it on the M4, and lifted off but the throttle was jammed wide open. I continued to accelerate at quite a rate (as you do in modfied WRX's on full throtttle) for a couple of seconds until I braked and turned off the engine and pulled over. The cable had become loose and binded- it had never been touched in years. Other things could be a faulty TPS or connection.


Hi,
I'm going spare trying to diagnose this one!
Problem is with my MY02 Outback. The accelerator is very touchy. Releasing it just a fraction and the car loses all momentum, lunging me forward. Deperessing it again ever so slightly and she re-engages and takes up the slack quickly. There is no in between and reducing to a coast can not be done smoothly; in fact, it won't coast smoothly at low speeds, not even on cruise control.
When descending down hills in any lowish gear, just engine braking, she can buck and hobby-horse. Depressing clutch stops this...until the next time.

I have read that it may be an ECU problem, or engine/tranny mounts, Throttle sensor, anti-knock sensor... but no-one seems to know. Mounts seem ok, very little backlash in drivetrain.

I have already installed a 2nd clutch, which did nothing except cost me lots of $. The mechanics aren't too sure either, so I'm releuctant to spend more on it for no gain! Scanner indicate nil error codes.

Anyone else have such problems? How should I tackle it?

subaruguy72
4th December 2009, 01:38 PM
Like Rally Stated....
Your Ride has 175k on it....things get worn with time, and the TPS gets ALOT of work over the duration of its life....

I had a 96 Outback with 160k on it Auto AWD....when I first got the thing it had very sporadic Shifting issues...I thought the TCU was at Fault...No codes.
I replaced the TCU....Didn't fix the problem....I was working as A Tech at my Local Subaru Dealership at the time....Having Subaru Diagnostics Computer at my fingers, I and 2 Senior Techs went and drove the car...
Same sporadic Shift and drive issues...Computer Showed No Faults and No codes...??????? So as a Collective Mind set ( 3 Subaru Techs ) we dicided it had to be a Tired Tranny....Clutches and baskets having slip issues...

I replaced the tranny With a Rebuilt unit, Same issues....:catfight:
I did notice my idle was a bit low, 650rpms or so, and if I had the Defroster on went into gear the thing would Almost die. So we plugged it into the computer and tried to reset all the Sensors to bring Idle back up...( this was after cleaning everything Egr,pcv,vacuum lines,etc.)
As soon as we touched the TPS sensor to adjust things, I got a code.
We checked the TPS parameters, and low and behold it was JUST BARELY OUT OF WACK at one end....:poke: :shrug:

Replaced the Silly thing , and The car drives Like a dream.....Mechanics have a saying ( Things Happen in 3's) after my Wagon gave us Fits, over the next 2 months we had 2 other cars come to the dealer with similar drivability issues...One was a Stick the other Auto....both ended up being a tired TPS...?

If it were me, I would get ahold of a Factory Subaru Service manual or get the Info you need from your dealer, All the Engine related Sensors can be checked statically on the car...The Factory Manual is going to give you the Best info, TPS will have static ( closed ) readings as well as WOT( wide open throttle ) Readings...I would investigate that as well as Idle air control Valve,and both your throttle cables, Main and Cruise....
If one of these is too tight, it will cause issues as well...I do a finger test

With your Index finger you should be able to push down from the top of each cable at the throttle body and get 1/8-1/4 inch of play before the throttle plate begins to move.....You want to verify the Throttle plate is Bottomed out at idle, if it is not, this can cause the TPS to read things wrong....

Hope this gives you better food for thought....Let us know what it ends up being.....:iconwink:

John.

Barry
18th December 2009, 05:25 AM
... If it were me, I would get ahold of a Factory Subaru Service manual ... The Factory Manual is going to give you the Best info, TPS will have static ( closed ) readings as well as WOT( wide open throttle ) Readings...I would investigate that as well as Idle air control Valve,and both your throttle cables, Main and Cruise....

Hope this gives you better food for thought....Let us know what it ends up being.....:iconwink:

John.

BUT Where on G*ds earth does one get a factory service manual? :twisted::twisted:

I'd happily pay for one for my 05OB, but they just can't be had!

homer56
23rd December 2009, 08:10 AM
how much is a tps thingy

Kevin
23rd December 2009, 08:26 PM
PM Hondaslayer (Ben at Hodges Subaru)

El_Freddo
23rd December 2009, 09:43 PM
Hmmm. Think I'll be checking my TPS as its behaving in the same manner as described here.

As for the manual issue, the factory manuals are hard to find at best but the Haynes or gregory (same company actually) manuals do the job good enough. What they don't tell me I make up/work it out myself...

Cheers

Bennie

El_Freddo
3rd January 2010, 07:16 AM
Well I checked the TPS on my EJ22 this arvo, this is what I got:

The on off switch (off at throttle closed, on at everything else) checked out ok. I need to find a set of feeler guages to check the change point of this at set throttle opening invervals.

The voltage at different openings of the throttle is meant to be 0 to 0.5 volts at throttle closed, as the throttle opens it should head up to about 5 volts at full open throttle. Reference voltage should be about 5 volts, I got 5.15v.
The voltage readings are all backwards. I'm getting 4.8something volts at closed throttle and about 0.1 at full throttle. So I'm guessing there's something wrong there. I've got a second unit at home in the shed that I'll be checking tomorrow after work, which ever is the better unit will be the one that ends up on the motor...

Any thoughts on those readings?

Cheers

Bennie

Rally
3rd January 2010, 08:07 AM
On my MY99 WRX- and I imagine Subaru would use similar principles on other models, voltage at fully open is 4.3v + or - 0.3v, and fully closed 0.5v + or - 0.3v. So it would indeed appear there is something not right if you are getting similar readings to what the manual says on my car.

El_Freddo
17th January 2010, 09:41 AM
So I finally busted out the second TPS I've got and checked some voltages - I got the same readings as the one that's currently on the EJ -> All backwards to what the manual (haynes) says it should be... I should check out one from the EA MPFI come to think of it - they may just be the same :D Things to do, things to do...

I really don't want to know the price of a new one but I would like it if someone else is able to back probe their TPS and see what voltage readings it gives at closed throttle and Wide Open Throttle (WOT).

Cheers

Bennie

dkselw
27th January 2010, 07:04 PM
BUT Where on G*ds earth does one get a factory service manual? :twisted::twisted:

I'd happily pay for one for my 05OB, but they just can't be had!

I believe you can download manuals from this site http://techinfo.subaru.com/html/referenceHome.jsp if you pay $34.95 for a 72 hour subscription.

joshuah
5th March 2010, 03:47 PM
Hi again,

I have taken the car to another place to look at and after a lot of sleuthing, he can't find anything wrong with the car or any of the sensors. Mind you, he did manage to pull the gear stick out of the housing while test driving it, which i will now have to pay him to fix...:twisted:

Anyways, this got me thinking about when the problem started, which was with the install of a solid flywheel and new clutch. Could it be that the flywheel installed is too light for the car? I have read that the dual mass flywheels are very heavy in comparison (9-10kg vs 5-6kg), which is the standard for my car. This would mean that now the flywheel has camparitively little inertia, which would explain why the car lunges and reacts so vigorously when the throttle is applied or removed etc...

What do you think of my theory? Is it possible to buy a heavier flywheel?

catchas.

J.

nipper
5th March 2010, 03:50 PM
Hi again,

I have taken the car to another place to look at and after a lot of sleuthing, he can't find anything wrong with the car or any of the sensors. Mind you, he did manage to pull the gear stick out of the housing while test driving it, which i will now have to pay him to fix...:twisted:

Anyways, this got me thinking about when the problem started, which was with the install of a solid flywheel and new clutch. Could it be that the flywheel installed is too light for the car? I have read that the dual mass flywheels are very heavy in comparison (9-10kg vs 5-6kg), which is the standard for my car. This would mean that now the flywheel has camparitively little inertia, which would explain why the car lunges and reacts so vigorously when the throttle is applied or removed etc...

What do you think of my theory? Is it possible to buy a heavier flywheel?

catchas.

J.

Was it an aftermarket flywheel? Subarus arent big fans of lightened flywheels.

joshuah
5th March 2010, 05:54 PM
I'm pretty sure. 1st clutch was a clutch-pro clutch kit and flywheel. They then installed a new Exedy clutch, but re-used the flywheel. Suffice to say it made no difference.
I see that many WRX owners and WRX wannabes put light-weight flywheels on their car for performance purposes. I am assuming they would experience similar loss of drivetrain kinetic energy?

Rally
5th March 2010, 11:34 PM
Dual mass flywheels were brought in to make things smoother. Quite why I am not sure because my WRX never had one and has always been fine. Duak mass flywheels are prone to issues where they become noisy. I think your weights are out re the flywheels, as the super light flywheels are, from memory 4 kg's and are no good for road use. Always best when asking for advice to include the bit about when the problem first started in your initial post- makes things easier for all.

Anyway, you have options. You could return to the dual mass flywheel- why anyone would put a super light flywheel in an Outback is way beyond me. Or you could try a normal solid flywheel. But before all of that, see if the people who replaced the clutch can tell you what flywheel was in the car. They should have mentioned it if the flywheel was non standard.

bru73
31st October 2010, 02:09 AM
to properely read a tps you need a scanner that reads live data stream,
engine off key on closed throttle it should read 0.45-0.48 max full throttle it should 100% you can also remove and using a ohm meter check for a glitch in it cant rember witch 2 termels to use just try tell you have movement move center very slowely watching reading reading shoud go up and down with out sckipping if reading jumps you may have a open on the winding in senser this is not uncomen check several times to varafie
:bananapartyhat::quitar::bananapartyhat::quitar::b ananapartyhat:

00 outback
31st October 2010, 04:23 AM
ive had similar issues with my outback, im starting to suspect the intake air control or the boro sensor. because ive got OBD codes that say large vac leak but there is no way.
ive rebuilt this engine myself all new seals and gaskets so they cant be it.
possibly a crack in the intake manifold but doubtful. let me know what you find out.
rally knows his stuff.