Legacy mega stutter!

[tebbyj]

Hi guys,

After searching and even hijacking someone elses thread i have finally come to the point im having to start my own thread.

I recently brought a 96 GTB car is awesome i love it, apart from the useless tyres and...

Everynow and then usually during short runs, and usually when just crusing at 50kph the engine will all of a sudden just die (well thats what it feels like) the rpm wont drop but car will have no power at all, if you give it more gas it jumps foward then dies then jumps hiccups then comes right again and your away. If you hold you foot flat to the floor it will hold at 2700-3000 rpm but no more, then take off like a stabed rat!

Can hiccup for any length of time, (feels like bunny hoping) then it will come right can be at any temp but usually when crusing at 50kph. Is throwing up no codes at all after repeated readings.

Have changed:

- Plugs

- 2 coils that tested bad

- fuel filter

- cleaned and tested maf ( seemed okay)

- knock sensor

Any help would be greatly appreicated. Im just at a complete loss but someone on here must have had this problem before. ;D

[Joker]

any codes from ecu?

[loner]

he says there are no codes, but there has to be...

[Joker]

ahh that bit was hidden : taken it to a garage of any sort?

[tebbyj]

No thats the stupid bit only code it had was 22 (knock sensor) which has been replaced so that code has gone,

No havent taken it to a garage, but I have had a few mates who are mechanics look at it and one said coils hence they were tested and changed. Thats it.... Must be something the ECU cant read?

[toad]

dont the knock sensors have to be torqued properly? as if they to tight they pick up every knock and if to loose pick up the vibration knock?

[ben-jamminn]

24nm and at 45 degrees

[tebbyj]

I dont know about torque but i know i installed it in the exact location and orientation as the old 1, prick of a job haha

[filthyrich]

What fuel?

[4foot]

have you tested the fuel pump .. It could be possible that what ever is causing the "hopping" "cutting" etc was causing something somewhere to knock with the old knock sensor (just throwing that out there) another thing that Ive heard of that could be worth checking on the older Legacy is the earth points, Ive been told that if the earth isnt very good it can lead to a hole bunch of random things going wrong ...

[tebbyj]

BP or Mobil 98 always, never anything less,

Havent tested fuel pump properly but i have checked it and hot wired it up and worked fine...

Wouldnt have a clue about the earthing thing.

[Marky]

So it\'s not a hesitation - like does it feel like the car is cutting out completely?

I\'d be looking towards something genuinely faulty or an earth / wiring fault, if you\'re driving steady at 50k and it cuts out, thats more spark dissapearing outright or fuel pump stopping completely - if that makes sense

If the fault was something happening with some load, then sure I\'d be looking at knock sensors afm\'s etc,

Maybe TPS being out of alignment - it\'s baaaarely open at light load, could be reading as closed?

You say it holds at 3k when you floor it - manual or auto?

[tebbyj]

Hi, yes feels like car is cutting out completely, then if you try to power out of it car bunny hops like its cutting in and out.

If you floor it it will hold the rpm you were doing relatively steady for 2-3 seconds then take off. Usually arround 2-3k rpm. Seems to be worse when cars cold.

Car is 1996 GTB manual 137ks cambelt done at 117ks and is completely factory standard apart from an alarm and turbo timer.

[titian]

would have to say possible TPS either setup or faulty. Marky could be onto it....Or the Gas pedal switch. My best guess anyway :)

I assume you did reset the computer after knock sensor was replaced.

That could be it too if you have not reset

[tebbyj]

Okay, will check that out tomorrow.

One thing i forgot to mention when you start it up from cold the idle will drop really low like very close to stall then pick itself back up to 1500rpm, possibly related?? ???

[Marky]

I am thinking a sensor related fault - the MAF can seem perfectly fine but be the cause of something like this, it would be my first guess based on what you\'re describing anyway. Knock sensor issues will cause the car to pull timing and at worst go into limp mode, but not cut out altogether.

I had one where the car drove perfectly normal but idle was horrendous - AFM/MAF was at fault despite the car driving perfectly the rest of the time. Ask if a local member can swap a known good one with you to test maybe, a lot of them are interchangeable between models and they are a massively common fault in subarus.

TPS adjustment can be found online... It\'s basically setting it to show a certain voltage when closed and open, its easy to do if you have a multimeter and is a free thing to "cross off the list" if nothing else? They can wander a bit over time.

Another thing worth doing is cleaning out the idle control valve - I don\'t think it\'s related at all to the cutting out issue but it might not be helping your cold idle either. It basically just gets gunked up with time and doesn\'t work that great.

[Munkvy]

Sounds like the Airflow Meter. I had similar experiences with mine when the first one died. Would just randomly cut out for no apparent reason, then come right again. Later on it did do a CEL briefly, then died completely. 2nd one I killed - no CEL, just random cutting out under part throttle only, very intermittent and frustrating (especially when you are silly like me and think its coils, so spend a heap of time replacing coils for no benefit!).

Next time it happens, as soon as it starts happening pull over and disconnect the AFM plug. If it starts to run right then, you have your culprit. Warning, don\'t drive far with the AFM disconnected, it isn\'t exactly good for the car.

[tebbyj]

Haven\'t had a chance to check tps yet but I do remember when we plugged the scan-pro in and read the current data I checked it and it definitely went up with throttle.

The airflow meter sounds likens more likely suspect to me because it does just feel like the car is running out of gas, I have a mate who has just got a gtb exactly the same so will see if she will let me "borrow" her afm for a little bit. Haha just to double check will put mine on hers and she what she says

[titian]

 tebbyj said:

Okay, will check that out tomorrow.

One thing i forgot to mention when you start it up from cold the idle will drop really low like very close to stall then pick itself back up to 1500rpm, possibly related?? ???

thats more like a gunked up icv/icu. Could be playing a part in this carry on you are experiencing...Not hard to remove and clean out

[tebbyj]

Could be somthing to do with ICV, if this were to stick open would it allow unmetered air into the engine causing a sudden leaning of mixture and loss of power??

But then why would the car try to open it while crusing??

Might be time for a can of subaru upper engine cleaner?

[Marky]

Put the cleaner through it anyway, does no harm.

ICV being stuck open would still be metered air (it\'s after AFM), so would cause similar symptom to throttle sticking open a tiny bit but nothing more.

[tebbyj]

 Marky said:

Put the cleaner through it anyway, does no harm.

ICV being stuck open would still be metered air (it\'s after AFM), so would cause similar symptom to throttle sticking open a tiny bit but nothing more.

Okay so its no that causing cutting out but may help idle.

Just found this on rexnet...

O2 SENSOR FAULTY

SYMPTOM: Rough idle usually cold (Closed loop) and jerky (surging)cruising acceleration.

WHY: Because the ECU isnt getting a proper reading anymore and the rough idle and surging is because the ecu is inlimp mode and flooding the car with extra fuel to protect it. Surging problems 9 out of 10 times are always fuel related.

sometimes faulty 02 sensor does not throw a CEL code. Well not in the begining anyway.

That sounds close, anyone experienced this before??

[loner]

hmm, I think the symptoms you have sound worse than you\'d get from the O2 sensor... my money if on the MAF.

[tebbyj]

Is there anyway to test the maf with a multimeter? Other than just unplugging it, because its an intermittent problem. Just so i can see if thats the problem before i go and buy a new one.

[darren23]

my 93 rs has the same problem just when its at low revs in 2nd gear