ImprezaRob

I dont know what it is with my car, but the last few weeks have been problems, problems, problems!!!

Heres the latest issue, which is concerning me quite a lot.....

When i accelerate hard in 3rd and 4th, and if i take the car over 5000rpm in 5th, out of the blue, the car will make a very sudden a dull sounding thud, and for a split second theres no noise, and there is no power either!

It does it so violently, suddenly, and without warning, that it almost throws me forward when it happens!

Power and noise will come back as normal after a split second, but it just happens again if i keep accelerating!

If doesnt seem to matter if the engines been running for 15 minutes, or an hour, neither does it make a difference whether its wet or dry!

What could this be???????? Having spoke to one mechanic (who did admit he was that familiar with subaru engines) he said it sounded like my big end bearings were on there way out, but also said it could be something as simple as a badly connected HT lead??

Has anyone had a similar exprience to me? Or does anyone have any idea as to what this could be???

Thanks in advance for your help guys.

Rob

paul w

sounds like overboost and fuel cut,try accelerating with less right foot and boost and see if it happens.

andy97

iTrader: (1)

What are the specifications on your car? ie have you modified it and what exactly have you done

Paulo P

iTrader: (42)

Just what I was about to say. It should happen easier in the cold weather.

ImprezaRob

its a 240bhp MY94 classic. Only mods are full de-cat, Apexi intake, Blitz NUR spec R exhaust system.

I've tried gently accelerating up to around 6000rpm and it still does it, not as severe as im not nailing it, but its still very noticeable.

It doesnt seem be matter with the weather, i remember it did it a couple of times back in the summer but only did it in 5th and was very occasional, but its doing it nearly everytime i accelerate now and has started doing it in 3rd and 4th!

With the possibility of it being overboost and fuel cut, what can rectify this? Would i need a new ECU or anything like that?

Paulo P

iTrader: (42)

do you have a boost gauge fitted?

ImprezaRob

No i havnt, theres one sitting in my bedroom that i keep meaning to get fitted..... I take it the boost gauge would indicate whether it was overboost?

Apart from the boost gauge, how else can i find out what the problem could be?

So it doesnt sound like my big end bearings?

Ben WRX Bug-Eye

Has it been running properly with that setup (full decat and induction kit) for a long time before now?

It does sound like fuel cut to me but no idea why it's happening on part throttle.

New_scooby_04

iTrader: (4)

I'd get the car to an engine specialist lke API mate and let them have a look. The conditions you describe do seem right for a boost cut (which isn't gentle) I see a Decat and induction with no remap and its been cold recently. Also it seems to be ocuring at the point at which the car develops max power. The kncoking noise is worrying though. Although If I understand it correctly, if it's the big ends, you don't have to wait till 5k rpm to hear it. If it is the big ends, then its a rebuild I'm afriad.

Speak to a specialist on the phone and see if they think you can drive it ok without doing further damage and if so drive it very gently to them asap and get them to have a look for you.

David at API is very highly recommended on here.

Good luck.

NS04

Paulo P

iTrader: (42)

Big end bearings would make a knocking noise and you'd know about it

Get some vacuum hose and run it out from under the bonnet and through the window to check the boost level quickly That saves fitting it just to quickly check the level

ImprezaRob

Yeah, i bought it in the summer with those modifications already done. It did it VERY occasionaly in the first 4 months i owned it (happend maybe twice?)

But now has become more and more regular, and im getting more and more concerned!!

Paul, no theres no other knocking sounds - in fact the car sounds peachy.... until this little problem happens!! haha!!

Right, i'll give API a bell and see what they suggest!

RichardC

This happened to my car shortly after I bought it 5 years ago and the problem was diagnosed as a faulty MAF.

This happened again recently and the MAF was tested as this was thought to be the fault, but it was testing OK, so they tried new coil packs and this did not cure it either. They then put my original coil packs and cleaned MAF back in and the problem had disappeared.

You could try these items first.

RichardC

Ben WRX Bug-Eye

Colder weather hence more likely to overboost than in summer (as said above). If you can get hold of a standard airbox and filter, i'd ditch the induction kit and try putting those back on - should reduce the likely hood of it happening.

16vmarc

Id get the leads changed first, I had problems with mines juddering under load, not cutting out though. But changing the leads sorted it.

ImprezaRob

I've spoken to David @ API Engines. He was extremely helpful.

He advised that i need to connect the 2 black cables under steering collumn. This will make the 'check engine' light flash, and a morse code type sequence should appear.

By counting the flashes will give a certain amount of points. Different points mean different problems, so will be doing that tommorow, and hopefully find out the problem tommorow!!

All this stuff has made me wonder about safety and reliablility and things like that! Would it be sensible to get a replacement ECU at this stage?

As previously mentioned its running a few mods, and im not always able to fill up with optimax/tesco 99ron.

Have been thinking about a Apexi power FC done by Andy F, or maybe take a trip to API as they seem so helpful?

Any advise appreciated, and thanks for the info so far guys!

Edited to ask.... If it is a MAF, how much am i looking at for a replacement?

APIDavid

iTrader: (4)

If I remember that's a late car then the MAF is under 80 quid + VAT. OOOps sorry just reread the above it's not a late car at all.

Mostly the early MAF's are more reliable than the 99/2000 one. Yes, they do fail but no so often. There are a number of different MAF's for the early car ranging in price from just under £200 to just over £300 from memory. We fit about 3 a year and see many cars every week, so not really a major seller !!

Reliability on solid state electronics is not an issue. By all means upgrade to an A'Pexi ecu, but not because you think the original is unreliable, they aren't.

A UK / Euro car will run fine on 97 fuel Optimax etc will always make it run better but strictly speaking isn't necessary.

Don't worry too much until we see the results of the ECu check.

Good Luck David APi Impreza / APi Engines
www.apiengines.com

ImprezaRob

Ok cool, i'll bear that in mind.

Thanks for your help on this David! Much appreciated.

typerchris

iTrader: (1)

Hi there i had the same problem about 2 hours after buying my type r this turned out to be a little hose that went to turbo so it was cutting the boost off. The bottom end has just gone this morning i'm gutted but car is on hp so i think the car isn't up to the standard it should be supplied.