MB2001

Having a problem with power delivery on a MY97 WRX. When I gun the car it's like it is spluttering and the boost comes banging in, seems to be over fueling. I remember hearing about a hose that can get blocked which causes erratic power, any one experienced similar?

Does this sound like the breather pipe/over boosting safety valve going into the inlet being bunged up, I'm just about to check it out this morning.

Mo

Could also be det...

Get this checked out ASAP b 4 'gunning' it any further.

Do you know how much boost you are running?

MB2001

Thanks for the reply, but now you have terrified me, it has a full custom ss sytem with no cats and when you are accelerating it stutters a few times as it spins up causing the car to judder.

It has supposed to be putting out around the 300bhp mark but I want to get it in for a proper tune.

MB2001

message for MO.......

I followed John S 's instructions on cleaning out solenoid valve hoses etc and still no joy, took the car down to Falkland performance and the guys there tried to fault find it. Starting with checking the plugs, 3 good and the one from the 3rd cylinder(the one that always seems to blow pistons) was looking a bit lean. fitted a boost gauge and replaced the plugs with a gap of 0.7 and tested the car, now the car seemed a little bit better but the problem is still there. The boost gauge was reading 16+ psi which the guys thought a little high and then checked the hoses and noticed a restictor valve in one of them( I think they said the wastegate) and reckoned it was not standard and causeing the high boost, now I have heard that the car should start cutting fuel at 14.5 ish psi but not to sure. the other sypmtom they noticed was a high idle speed of around 1150 rpm and a slight engine wobble when idling in the workshop, also when starting the car from cold it can take around 8 cycles before firing up but not when hot. this then made the guy think that it could be a timing problem, maybe a cam was out by a tooth but we run out of time so I eased the car home without using to much boost and then stripped the cover off to check the timing marks and they are perfect, all lined up etc so now I'm think what the hell is wrong is it to much boost and ecu not keeping the fuel supplied or is it a dodgy injector or worse still is that third piston on its way out as the guy told me of a car last year they had in that had similar symptoms and then melted the piston, resulting in a second hand engine being the fix. I really dont want to have to do this as the car has only 40,000 kph on the clock with a service history from first import...reason I bought the buggar!

If you have any ideas or know anyone whos been to hell and back let us know......thanks again.

MARK BRANDIE

[Edited by MB2001 - 4/29/2002 11:15:33 PM]

Mo

Mark,

I'm not sure where your fuel cut should be or if it has been modified. Do you have a bleed valve anywhere, check around the solenoid area in the engine bay.

When you say the boost was 16+psi whats the + for? Was it holding 16psi or did it overboost at any point?

I know that Falkland checked your plugs but it may be worth checking your coil packs aswell, these are prone to failure. Check out Scott T's post with pictures towards the bottom of this thread.

Coil pack testing

The resrictor should be their however it's size may have been altered, changing the size and/or location of the resrictors will cause different boost characteristics.

The position of the restrictor will significantly affect the way the car boosts, the further away from the solenoid (towards the turbo) the better the control. This assumes that you are running with a three port solenoid and not a two port.
If you use one in the turbo to solenoid line and balance that with one in the vent pipe then you can play with the sizing to achieve virtually no overboost.



[Edited by Mo - 4/30/2002 12:57:02 PM]

SIBBO

Hi Mark I also have a 97 STI which i have own for the last 3 years,I have the same thing happen around 4500 to 5000 rpm it would miss and back fire.I spoke Barrarts motorsport dept and the first thing they said was the plugs could be on the way out.I asked which plugs I should use and NGKR 7 11 was the plugs which they use in thier rally cars. So I replaced the plugs, to do this you have to remove the airfilter which I have a TGI filter and it was in need of a clean.Since I had the air filter out I also cleaned the small pipes from the manifold and the turbo. My car seems to be fine, THE BEST IT HAS GONE.

Hope this helps Tim.

MB2001

Thanks guys,

I removed the restictor on the wastgate - turbo hose and hey presto problem solved but the power is down a bit, I am still waiting for boost gauge to arrive in the post so as I can check the pressure. I'm now offshore for 2 weeks so I will have the missus driving it and I want to check ther plugs again when I get back to see if the 3 cylinder is still running lean, hopefully it,s going to look better than before also fitted platinum plugs so maybe running better.

I plan to make up a maunally adjustable valve so as I can adjust the restiction and find the point at which it starts to splutter.

Also thinking that because there is a full custom exhaust with no cats, surely this requires some other mods like fuel remap or better air filter etc, I'm thinking its a bit harsh for the engine?

I'm planning the full link system for the car right down to the serial cable for my laptop, This is all too interesting and I am looking forward to tweaking and tinkering with the gadgets.

Sheepsplitter

MB2001:
Rough running and bad idle can also be the symptoms of a failing Lambda sensor. Funnily enough I had this problem only a few weeks ago. You might want to get it checked out.
The Lambda sensor is only used at low (ish) revs, the ECU goes closed loop at higher revs and doesn't use the sensor, so if things improve when you rev it that could indicate the problem.