doobiedooo

I have a MY98 Impreza and last night noticed a wierd problem....

When I accelerate hard in 4th or 5th (doesn't seem to do it in other gears) the car hiccups quite violently at exactly 3500 rpm, then carries on as normal.

It seems to be worse with a car full but I also managed to recreate it this morning with just me on board.

Help! Any ideas???????

thanks.

doobiedooo

SOMEONE? ANYONE!?

ronniebiggs

If youre accelerating hard in 4th and 5th the boost will rise to peak boost!! If you have a boost guage fitted, what boost you getting. Sounds to me like youre hitting the inhibitor. But without more info Im just guessing really. I have a 300bhp (self proclaimed) WRX import my 94 and I fitted a Twin dump downpipe. If I get into 4th and 5th and plough my foot to the floor the boost swings up to 1.4 bar and then the car dies!!!

I think this is youre prob!!
Hope this helps Ronnie

doobiedooo

I'll start by apologising for my technical ignorance!!

Apparently the car is standard apart from the exhaust. I've only had it a month or so.

When you say you think its hitting the "inhibitor" is this some kind of boost limit on the Turbo? I don't have a boost gauge fitted so I don't really know what the car's doing boost wise at the "hiccup" point. If it is hitting the inhibitor would that indicate that the car has had its Turbo "fiddled" with at some stage? Should it be able to max out in standard trim?!

Ta.

ronniebiggs

Theoretically the Turbo should not max in standard trim!!! However you dont know if the car has been fiddled if youve altered the exhaust. How fare have you gone? If you have decatted the car. Downpipe and middle cat, then you may hit the inhibitor.

The inhibitor= a boost limit where the ecu says f**k no more boost and depending on the model just lets the car rev out as to speek and reduce the boost (like my car 1994) or on other models it just feels like your hitting a brick wall as your car trys to deaccelerate without your concent sort off like a sputter effect, but worse and it does this until you let your foot off enough to reduce the boost levels!!
Have you had the car from new? If not:

1st think to check is the ECU, pull back the passanger side carpet on the floor. theres nothing holding it in, just put your hands on the top and pull it down, minding the plastic trim on the left, as its tucked behind it. once this is back, you will see a kick panal on the floor with 5 screw/bolts in. Take them out and remove the panal. you will now be looking at the ECU!!! Read what (if anything) is wrote on the ECU!!

Also check there is no boost controllers attached. Check this by looking near the turbo to see if there is a bleed valve, dawes device etc.
Get back to me if you find anything on the ECU or a boost controler
Regards Ronnie

ronniebiggs

Any luck???????

doobiedooo

Thanks. In the office at the moment so can't go and rip up me carpet!!!!

Had a thought though. I've wellied the car plenty since I've had it :-) and never noticed the problem before??? If it was because of an upgraded ECU wouldn't it do it always?

Cheers.

Pieman

Sounds like fuel-cut due to overboost – perhaps the car is decatted?

doobiedooo

How do I tell if it is "decated". The car has a "bean can" exhaust but I'm sure its just the rear section that is non-standard.

ronniebiggs

Overboost, Hitting the boost limiter=same thing!!
You tell if the car has been decatted by firstly lifting the bonnet. Get your head right over in the top left and see iff the car has an air scoop that is directly above the turbo (the bonnet also sits on the top of this) so the air comes in througgh the middle scoop on the bonnet goes into the intercooler and if you look at the bonnet vent youll see that its split up into a left hand section and a much larger right hand section. The left hand directs the air into the air scoop under the bonnet that im refering to and cools the turbo by blowing air over it.

The first clue that it may have a decat downpipe is if the air scoop is there. If not look at the back left and locate the turbo and you will see the downpipe coming out the turbo. See if the pipe goes from 3" to about 5" like a bulge in the pipe. If so its catted if it stays 3" and goes right down without cahnge its decatted. If the Air scoop (previously refered to is still on the car) Just do your best to try and see the downpipe.

Secondly get on your hands and Knees near the front wheels and look under the car at the top of the middle section of exhaust just before it starts to go into the downpipe and see if you can see again a swell. But this time it looks more like a small middle box in the exhaust. If not this one is removed. What you may find is one may be removed and the other still may be there. The mainly restrictive one that will cause the most probs is the downpipe.

I know its quite a long thread but I have put as much detail as possible to try and make it easier. But dont forget check the ecu, it will only take you between 5-10 mins even though you have never done it before.

Need any more help, either e-mail by profile or ill keep checking this thread as and when Im on the net.
All the best Ronnie

doobiedooo

Thanks ronnie. I've emailed you.