Can any of you techno heads help me out?

What part controls the boost?

is it the small unit on the left hand side when looking inside the engine bay?

If so do the play up?

I have got a 1992 Legacy which has been loosing boost every now and then, it could be boosting well and then all of a sudden it has no boost and reminds me of driving my wife's 1400 Astra and it could stay like that for 10 minutes or so and then all of a sudden it's working okay again?????

YOU HELP PLEASE WOULD BE GREAT........

 

The ECU controls boost parameters.
The turbo provides the boost pressure.
The wastegate opens at a set pressure, usually 0.5 bar but the boost solenoid (on lefthand side) opens and shuts several times a second to act like a bleed valve to achieve the boost pressure set by the ECU.

 

So, why do you think i keep looseing boost every now and then????

 

intermittent ?

Possibly your BOV/Dump valve sticking open ?

Or a leak somewhere else.

J.

 

Sometimes, if the ecu has detected a poor running condition, it will default to a low boost setting. Not sure what condtitons it monitors do to this, but at a time, my legacy chargecooler pump was not working, and the first good blast down the road would be fine, then all of a sudden nothing, boost dropped to about 5psi. It might stay like this for 1 hour, or till i switched off and started again, it varied from time to time. Once the pump was fixed, all was fine. I dont think that the std ecu actually monitors air temps, although this would be an obvious reason for dropping back boost pressure for safety reasons.

 

J

I shall change the dump valve with another one i have but it does not seem that type of problem.

It seems as if a switch is playing about????

 

Worth cleaning the boost solenoid with brake cleaner(NOT BRAKE FLUID)

 

When you say you sometimes get no boost......do you mean no boost whatsoever?

A

 

This is exactly what I get with my Impreza! (MY96)
You have my sympathy - it's lousy with no boost!

I will be watching this thread!

BTW, there is probably something in "Drivetrain" that may help
If only search worked...

 

AlanG

Correct, No Boost at all...

 

If you get no boost at all, then could be a couple of things, like loose boost hoses (losing pressure) or the wastegate is opening ( weak/ broken spring in wastegate actuator). The dump valve may also be faulty, continually dumping pressure back into the intake system.

Check all hoseclips are tight on the positive boost pressure side, check the hoses associated with the dump valve as well. While your at it, check there are no cracked / split hoses and also check the boost control hoses (4mm) have not been tiied together with a tiewrap therefore cutting off air supply.

A

 

Just been told by mu ECU code 31 - Throttle position sensor abnormal. Could this be related to the problem.

(It's definitely saying 31, not 32 - I checked three times...)

 

Alan

Checked all hoses already, but if it was a hose wouldn't it be doing it all the time?

 

Not necessarily. I was taking it from your first thread where the boost came and went.

Have you checked the wastegate actuator?

 

Check the hard crappy plastic pipes under the chargecooler. The clips may be loose here, but it can be hard to tell because of the hard plastic pipes. Could there be an air intake restriction of some sort? or possibly an exhaust blockage?

 

ive also been havin probs with boost,sometimes at 40mph sometimes a bit faster!!!the car seems to kangagroo and the boost guage goes from +14 up to +18 and moves back n forth between the 2 figures.Iam going to my mates garage on monday he is gpoing to check the code 31 out(MY97)will post results monday eve

urs

Andi

 

prob sorted

removed turbo heat shield,then remove small c-clip that holds the actuator in place(or if ur me,the long brass coloured rod(with nut on it)and screw the nut clockwise about 2-4 turns.u may find out u need to wind it back/or forth once u have driven the car.My97 now tops out at 13-14psi(instead of the usual 18!!!!)

and the kangarooing has now gone completely...

andi

 

I wish i could give the same answer....

After a long conflab with Alan on Saturday i was hopeing the problem was going to go but directly after speaking with him for the last time i tock the car down the car and the problem was there again.

This time you could hear the whoooosh whilst accelerating with my foot hard down at about 3500 RPM, with the window open you could suddenly hear the whoosh die as if some one has shut off a tap.

I then stopped the car and done a ECU Check, no fault reported, i then drove the car for about 2-3 miles and then to boost was back again.


Someone must have come across this at some stage before????????

 

Like Deep said clean out the solenoid valve and pipework with brake cleaner. Could be a sticking valve.

 

Harvey

Already done that still no joy

 

Mailed you Dean