I have a fully Subaru serviced unmodded UK MY99 Imp Turbo.

Its had engine problems continually for 18 months
(3 replacement engines). I have several posted
responses from people with suggestions to the cause.

I have had new heads, short engine, pistons, turbo,
oil pump, fuel filter, injectors, ECU, plugs, oil,
filter, etc to name but a few, all under warranty.

Its never thrashed from cold. Always cooled down
before turning it off. I do not use 95 oct fuel.

But it still runs rough most days, but will suddenly run
perfectly for the odd day. The difference is phenomenal
and not just a few bhp. Boost waivers, power waivers,
etc, etc on different fuels (97/98), under different
conditions (hot/cold/fast/slow).

The failures have all ended up with holes in pistons (different ones)and loads of oil everywhere. No noise on failure, no fault lights, no warning (other than bad running as usual), not even
any smoke (initially).

Its due a rolling road session soon.

However, I would like to systematically replace parts, out of my own pocket, that COULD have something to do with the bad running.

Can anyone please provide a list of parts, with descriptions of what they do, possible cost from Subaru and part number would be good. For all of the "things" under the bonnet that could cause the problems.

ie,
Boost Modulator Valve (controls boost ??),
Fuel Pump (do these fail, can they be intermittent),
Temp Sensors?, Crank Position sensors? and any other 'things'.

The more info, examples, etc anyone can provide for any of the parts that play a part in the running of the engine, the better.

I hate the car at the moment and its been nothing but trouble.
I have had several turbo cars accross 13 years and none of them
have been as much hassle.

Help!!!

Many thanks in advance,

MKC.

Fuel pump, fuel pressure regulator, MAF sensor, knock sensor.

It sounds like it is detting. Common causes for this are not enough fuel or too low MAF readings.

If everything else is OK and the car is not run on 95 RON as you say, I doubt that a failed knock sensor would be enough on the standard ECU to cause a knock related failure.

There should always be a cause found for detonation related failures like it very much sounds like this one is if at all possible as otherwise it probably will happen again.

The rough running does have a cause, just needs time and a methodical check of everything.

Armed with a fuel pressure gauge (which can be read on full boost to confirm correct operation of the regulator and fuel pump), knocklink and someone who knows what they are doing checking your car with Delta Dash I think you would find your answer. I would suggest doing this rather than start just replacing things. They would not be changing anything just fault finding.

One sensor which can lead to major problems which you have not mentioned is the MAF sensor..! This can be replaced for £70..

Dan:D

As JB says - delta dash logs would help, along with some back up from "real world" gauges (knock link and boost gauge) so that you can verify what the ECU is telling you and see that it's making sensible decisions based on the data it gets.

This should be done before randomly spending money on sensors.

A willing friend with a similar car might be persuaded lend you a MAF sensor for a while for the testing...

I sympathise, as it will be a quite a hard task to track this down. But by the end of it, you'll be an expert on Scoob engines ;)

Thanks for the info so far.

I have booked a rolling road session with G-force in Aylesbury for next week. They have a Delta Dash and will be able to monitor the ECU, air/fuel, boost etc. Its having a Subaru service in the mean time, to eliminate anything that may interfere with the troubleshooting.

I am still interested, for after the RR session, to know what
bits under the bonnet do what, if there are any left to describe.

Regards,

MKC

have a look at http://www.jimclarkeracing.co.uk/~scoobynet/my97-98/

It's not for your model car, but it may just provide you with an idea of what goes on. BTW It's a fairly major download...

Nice One. Download frenzy is now complete..!

Thanks,

MKC.

Stoopid question, but what's a Delta Dash??

Just checked with Subaru and MAF is £191 + vat.

They mentioned a MAP sensor.

Which one could cause boost problems or were you referrning to ?

Thanks.

The MAF sensor itself is not £191 +vat. That price is for the whole setup which you will not need. Do a search on MAF cause there was a post a while back with the part unmber you require.

Found it for you look here

Hope this helps.

Thanks. I have the info ready now for after my rolling road session. I have added a reply to the MAF post asking for a description from personal experience of the symptoms from a knackered MAF. My car NEVER has a problem idling or running below 2k, which seems to be the standard symptoms of a faulty MAF.

Cheers again.

Colin...

Replacement engine is one symptom.

Roughness can be different on different cars.

Some run great because they are lean and advanced and then blow up from all the damage from the accumulated detonation.

You can't sort your problem by symptoms, to find it you need to methodically check every possibility. Also I don't think you'll get there by just replacing things, but if you did want to blindly replace something it would be the MAF, but you would want to satisfy yourself as far as I am concerned that you have found and fixed a problem rather than scratching where it doesn't itch.

Also I think your priority is not particularly a rolling road run but diagnostics.

Rolling roading a dodgy engine is enough to blow it up.

Thanks.

Sorry, I did not word that last message very well...I am having an hours diagnostics on G-Force's rolling road in Aylesbury, not just a rolling road run. I will mention that I am after diags and not a bhp figure and keep revs at normal driving rates.

The symptoms on the car are so bad and so constant that if the problem is cured it would be more than apparent. However, I will only be getting replacement bits when some useful diags results are available.

Knowing the price and part numbers of the bits it COULD be will help me prepare for replacing them after the RR. I will need to know what the rolling diags results mean too!! I presume that a diags will show any discrepancies between sensors saying there's plenty of fuel and the fuel reading saying there is not...

Any advise in advance of what certain results could mean would be welcomed.

Thanks again,

MKC

God...its getting worse...

For 40 minutes of 60-70mph driving last night is was holding back and driving me mad. When I put my foot down from 3k, the turbo hiss is not there !!! the revs build smoothly but held back all the way to 5k but there's no turbo hiss and power is lacking. Stopped and started the car twice and after second stop the hiss started again (but still not running very well). The stopping and starting of the car would seem to indicate an electronically controlled device being knackered..

Its had a new Turbo and actuator (after engine one failed).
It had this same problem both before and after the new turbo.

If the MAF is knackered, does it not just affect the ignition?
Is it supposed to stop the turbo hissing ?

Does this none operation of the turbo symptom up
to 5k make any difference to the possible faults ?

Am waiting for rroad diags thursday but am still
interested in any suggestions or explanations...

Thanks again.

Colin...

Sorry Colin, too many options for me to run through them all. Let the guy see the car and see what he can do for you.

OK...I will take it easy until then.

Thanks anyway.

I found that my car is holding back at 3k+ because its running leaner than a weight watchers sausage !! I will not be driving it until its next rr visit now (Thurs)

Delta dash results at full throtle up to 4.5k;

throt sensor vtage 2.34v
max inject dut cycle 25%
knock correction -1.5
ignit timing 28 degrees
air flow sensor voltage 3.22v

Lamda Reading 1 to 1.1 up to 3500 revs, then it steadily increases to 1.3 at 4500revs (when it should go down).

boost increases smthly to 3200 revs and holds steady at just over .8bar.

I need to ask Subaru if ECU map load point is derived from throttle position or MAF SENSOR?

And does the car have a full throttle swich?

Given all of the above, can anyone answer the questions and suggest which parts of this may now show which devices or sensors may be at fault?

Also posted this in drivetrain...

On thursday next week the rr place will monitor the fuel pressure (was too hot & late tday). Should I note any other readings for coparison with other peoples ?

Thanks Again...Colin (logged in from home (not MKC account))