dal7on

hey people, im new here and ive just bought a 1996 subaru impreza wrx and have a problem with it that i thought someone might be able to help me with...

when driving, at around 4 and a half thousand revs the car jerks quite bad, it runs and drives really well other than this fault. when it happens, if you take your foot off the accelerator then put it down again, sometimes the fault doesnt occur, so i would say its an intermittent fault.

i also have an fto and had a similar problem with that, but it was a gearbox sensor that caused it.

ive been told by a source that it could be a gearbox fault and me personally think its a sensor or something like that but im not positive and not sure what to do or where to start, so any info would be a great help,
thanks.

Glowplug

iTrader: (8)

If i was you, i'd start with a fault code check, see here.

If that tells you nothing then plugs, leads and coil pack would be my next piont of call.

dal7on

ok thanks for the advice. what if the things you suggested didnt resolve the problem? what would you then suggest?

Glowplug

iTrader: (8)

Cross that bridge if/when you need to.

I wouldn't be thinking gearbox though from what you have said.

saiklon

Bad misfire at 4.5krpm is caused by limp mode. One common cause of this is a non-working speedo. A diagnostic check will tell you exactly what is causing it.

dal7on

it has this misfire/jerking fault in every gear at 4 and 1/2 K and its coming up with error code 46, but im not sure what this code is??

Glowplug

iTrader: (8)

46 is 'Neutral or Parking Switch or Circuit'. Although, not nessisarily on an Impreza, that would be 51. You sure you counted right??

EcU reset/codes info here.

dal7on

im pretty sure i counted right yeah, would the "neutral or parking switch/circuit" cause the problem im having do you think??

Glowplug

iTrader: (8)

I thought it was only applicable to autos. I could well be wrong though.

As i said, 51 is the usual code for that fault, 46 does not really exist, in fact none of the usual codes end in 6.

You could try resetting the ECU, then see what it reads.

dal7on

could you tell me how to reset the ECU? do you know how to rectify the fault if it is actually the "neutral or parking switch/circuit" to stop it from jerking like it does? or would resetting the ECU cure the actual problem?

Glowplug

iTrader: (8)

See the link in post#7.

It may cure it. As i said, i thought that switch was only on autos, so no, i wouldn't know how to rectify with out a bit of research first.

dal7on

im just looking now for a bit of information about them. on 1 site it says they are only on autos but on another site it says they are on manuals aswell then gives a guide on how to adjust it explaining that if its position is incorrect it may operate eratically.

Glowplug

iTrader: (8)

Just had a quick look around, and yes it does apply to manuals too. How ever, it does not give the symptoms that you are experiencing. 4000-4500rpm is around the 'limp mode' limit for the ECU.

As suggested earlier, reset the ECU and redo the fault diagnoses. This will be the truest reading, as old/previous faults are stored by the ECU will be erased by a reset and only new faults will be shown. And it only takes 2 mins.

dal7on

its error code 45 not 46! which i believe is the Pressure sensor –Pressure exchange solenoid valve? would error code 45 cause the car to react the way it is i.e jerking at around 4 and 1/2 K when in boost, in every gear?

Glowplug

iTrader: (8)

Yes i would think so, as it is a boost/pressure related sensor and the car is playing up on boost.

Did you try a reset?

You should be able to pick one up, usually complete with a BCS cheap enough in the for sale section.

dal7on

yeah i tried a reset but it just gave me error code 45, tried to wipe the code aswell but it didnt seem to wanna go off, im guessing cos the fault had not been rectified?

Turbotits

iTrader: (2)

Give the boost solniod a clean> it may have had it but a clean with carb cleaner often helps and costs nothing

dal7on

ive now replaced the Pressure sensor/Pressure exchange solenoid valve but im still getting the same error code(45). ive tried resetting the ecu but i dont seem to be having much joy resetting it, is there another way of resetting the ecu?

Splitpin

If the reset method you are trying is the one involving connecting the black and green plugs, and then driving gently for a bit, there's no point asking us about another way to do it.

Bottom line is that if that method won't give the OK signal and still, consistently, gives you the 45 error, you are still suffering the error. That's the bottom line.

There are a number of different things that will cause the 45 error code. A duff MAP sensor is one of them. A duff pressure source exchange solenoid is another. The other possible causes are fault(s) in the wiring loom between either or both of the above and the power supplies/ECU.

If you've replaced both the sensor and the solenoid, and are still experiencing the trouble code, then you need firstly to double check whether the new parts you have fitted are good, and if they are, start checking the relevant bits of the loom for breaks or shorts. Dodgy/corroded/loose connectors would be another thing to check while you're at it.

dal7on

ive just took it for a drive and its still jerking as before but not as bad. before it was 1 big bad jerk, but now it seems to be a lot of little ones :S

Glowplug

iTrader: (8)

So, which of the parts in the pic below have you changed?

dal7on

the big metal silver thing in the middle, replacing it has made a difference but not totally fixed the problem

Glowplug

iTrader: (8)

That is the Boost control Solenoid (BCS).

The part on the left is the Mass Air Pressure Sensor (MAP), and that is connected by the pipe to the part on top which is the Pressure Exchange Solenoid (PES).

As Splitpin pointed out, both the MAP and the PES, if faulty will bring up the error code 45. Check the security and condition of the associated pipework. If all is well then replace the MAP and/or the PES .

dal7on

do you know where i can get a map sensor and a pressure exchange solenoid? finding parts for this car seems to be harder than my '94 fto :S

Glowplug

iTrader: (8)

This may be of use to you.

Also, the 'For Sale' section on here is always a good place to trawl.

dal7on

my god ive looked high and low on ebay lol where was that hiding. i must say mate uve been a great help, really appreciate it.

Glowplug

iTrader: (8)

I just typed in 'subaru map' .

It's no problem mate, that is what SN is about. If we can, we will.