snOOpy86

iTrader: (1)

Help, driving to work this morning and about half way there i went to overtake a car (motorway) as it came on boost the car started jolting so instanly backed of (as you would) so limped it to work under 3k and no more than part throttle.

CEL light is on and iv pluged the 2 black connectors together to fault find

* 24 Air control valve or circuit (exc. Justy); Idle speed control solenoid valve (Justy)

* 44 Wastegate duty solenoid (turbo)

at 1st i thought it may be a split hose some where but they all look ok and really dont know where to start from here.. plugs, lamba and maf were changed at the beginning of year (i think)

any ideas?

Splitpin

Could be any number of things, but, to help us narrow it down a bit, when you started overtaking, did you actually feel the car come onto boost and start to pull before it jolted?

If so, likeliest explanation for the jolting was that it was boost cut secondary to overboost. First thing I'd look for would be a loose or split pipe between the turbo and the boost control solenoid (which is on a bracket fixed to the offside suspension turret). If you've already looked once, I'd check these again just to be certain, maybe even take 'em off and have a look indoors just to rule out any splits on the underside where you can't see in the car.

Also, what MY and type is your car, and do you have a boost gauge?

arumdevil

also, reset the codes and see if the problem comes back and if any of the codes come back...

snOOpy86

iTrader: (1)

Hi mate, sorry i knew i forgot to mention something! lol, its a 2000 turbo.

i do have a boost gauge and as soon as it starts to make boost i get a mass of hesitation/jolting.

i do have some spare silicon hose at home that i can replace the old hoses with, what does the boost soleniod look like? as there is 2 units bolted to turret with wires connected and a unit below (circular) with what looks like an adjuster on the top with a hose coming out the bottom?

Glowplug

iTrader: (8)

The boost solenoid is the circular unit with 3 pipes coming off (top,middle and very bottom) the 'adjuster' on top is not, it is the pressure exchange unit. See pic below, hth.

Boost Solenoid Plumbing

Splitpin

Just to clarify, are you saying it's a 2000 model year Impreza Turbo 2000, or an Impreza Turbo 2000 of some other year? What is the fourth character of the Applied Model code? (ie what's the asterisk in GC8*K8D?)

Does the hesitation and jolting start literally as soon as the gauge flicks past 0 and into positive, or does it get a good few psi first?

Wouldn't change the pipework just yet - especially (if you have a two port) the bits that link the compressor outlet, wastegate actuator and t-piece.

The thing that looks like an adjuster is, as B13 says, the pressure sources change solenoid. The boost control solenoid is a larger cylinder with an electrical connector and either two or three pipes running to/from it.

snOOpy86

iTrader: (1)

its a uk impreza 2000, w reg 2000.
it seems to happen as soon as it makes any possitive boost.

Splitpin

Thanks for the clarification. In that case your boost control pack won't look like the one B13 linked to earlier. The boost control solenoid is the large cylinder nearest the wing with the blue electrical connector and two pipes running to it.

Still a number of potential causes. From what you've said re. this starting as soon as you get any positive boost, a split pipe is probably less likely an explanation, as you'd need to be seeing the boost spike above 1.2 bar before fuel is cut. Take it your boost gauge is plumbed to the "spare" takeoff on the front of the inlet manifold btw?

Would be worth taking the boost control solenoid pipework off and seeing if it's full of oil (or oily black gunk). If so, time to put ECU in test mode and flush the solenoid and pipework with brake cleaner.

snOOpy86

iTrader: (1)

if i was to disconnect the solenoid what effect would that have on boost?

Splitpin

If you disconnect it electrically (i.e unplug it) the engine will run on actuator pressure, so should get 0.7 bar or so boost unless your pipework is full of oil, in which case could do exactly as it did before, or some variation of it.

If you disconnect the pipework from the solenoid, the turbo will surge and overspeed the first time you get it properly spooled up, and either kill itself or your engine, or both, with the ECU trying to mitigate the damage via fuel cut.

If you're going to remove the solenoid from the system as a diagnostic check, the way to do it is to use one of the lengths of pipe to directly connect the compressor outlet to the wastegate actuator. This should give you that 0.7 bar or so as mentioned earlier.

snOOpy86

iTrader: (1)

reset the ecu last night and it came back as 23 - maf sensor
so disconnected it to see if it made any diffrence and was still the same, so today i ordered a new maf from my local subaru dealer at the cost of £103.00!!!
fitted it in my lunch break and took it up the road to reset ecu again and started flashing the all clear signs.
disconnect plugs, drive to garage, get fuel and a quick drive back to work and everythings back to normal again at last!

Glowplug

iTrader: (8)

Cool £103 well spent

arumdevil

wow, I was under the impression that a MAF from a dealer was closer to £300?

good result

Splitpin

Nice job!

That number's not far off for the earlier sensors, and it's about right if you buy the complete assembly for 99-00 or newage. The sensor insert has only recently gone above a hundred quid dealer retail.

arumdevil

I guess my 98 legacy is the old style one then