Can anyone help,
I have recently started to feel a power loss at the top end of the rev range in higher gears (5000rpm plus) it feels almost like a misfire. I have been back to the dealer who has put on the computer and can find no fault showing,a reset has been done, but the fault is still occuring.
My car is a uk STi 7 running front cat only and itg filter(change at 3000 miles)no problems at first but now with with 6000 miles on the clock and air temperatures dropping, have i got the dreaded overboost or can anyone shed any light on what it might be.
Thanks Steve

 

If this is a stupid reply, ignore it, but have you had your plugs out/changed/plug leads diturbed? When my '98 turbo misfired, it was a single plug lead breaking down at higher revs. It didn't show up on any error codes, and it took the dealer 3 goes to find it.(Despite me telling him the first time, that my old boy, ex RAF Lancaster electrician, said to look at ignition......he just laughed.)
Alcazar

 

Steve,
if it feels like pulsing (on off on off power etc) then its overboosing, i think the fix for this is the restrictor plug.
When people were talking about decatting the STi7's there were problems with boost spikes (1.7bar ) and the way round it was to change the restrictor plug size to 1.25mm, this cured the problem

Tony

 

Should also say that even the supposedly "dry" foam filters can naff your MAF sensor up so check that there aint no goo in your airbox!

Tony

 

Alcazar,Thanks m8 When it goes back to the dealer i will get them to check,
Tony, I must admit I share your suspisions, it does feel like its on/off, but I thought the over boost issue was only when people did a full decat not when you leave the first cat in place, suppose I should get a boost gauge fitted and change the restrictor anyway, thanks m8

Cheers steve

 

Dont think its anything to do with removing the small cat, mine has the same as yours plus Jaceyboy has his done too and neither of us have this fault, infact the cold air is making them really zippy.

 

I think I can safely say I have had experience of 1.7 bar boost spikes LOL.

Having run various combinations of exhaust, Carolyn's STi7 is running a totally standard system now and does seem to hold back at 5000 rpm plus sometimes, but mine is running a Scoobysport decat from the downpipe back and has no problems.

Ideally you need to put a boost gauge on it to see what is happening. You should not be getting any more than 1.2 to 1.3 bar peak boost with the exhaust, and this will NOT cut the boost back. That's the problem with the STi7, the boost control solenoid can't react quick enough with the standard restrictor to cut the boost back quickly enough.

I would swop the ITG out for the standard panel filter and try that - the STi7 is fussy about induction it would seem....

 

Tony, you were right about the ITG filter, took out the filter and yep loads of goo in the air box. Cleaned it out and took Daves advice and changed back to the original filter, but I aint had chance to check it properly yet.

I must say that the ITG looks in a poor state considering its only done 2400 miles, it was dripping with Green goo.

Forgive my ignorance but where is this Maff sensor and could it be naffed up with goo.

Thanks for the help guys, Steve

 

Steve

I doubt it is the MAF. We have had a similar fault in and cleaned the MAF, to eliminate it. It made no difference at all. The customer has since changed the MAF, again making no difference.

The 01-02 MAF is a completely different design. The air enters a cartridge, turns 90 deg, goes up to the sensor and then returns back down to the flow.

Its extremely unlikely that any polymer would get drawn off your ITG and if it did, it would hit the bend in the cartridge and not reach the sensor itself.

Check that the filter is correctly installed, as if it is not, turbulent air can get passed the edge of the filter and this can cause erroneous readings.

 

Thanks Pete, will check the fitting, but when I took out the ITG it did seem to have been fitted correctly. the car you refer to, has it also only the front cat in place ?
Steve

 

It has no cats.

 

I like Jacey and big goon also have a decat centre with front cat in place. Seems ok and like Goon says feeling quicker with the cooler air. Boost gauge goes upto about 1.3 and drops back to 0.9 ish.

Jas

 

I recently DDash'ed an STi7 which was retarding badly above 5k5 (-3 to 5 degrees instead of normal + 10-15) - sent the owner back to Subaru as it was under warranty.

Subaru have come back to him saying it's a known problem.... Anyone have anything more, and does the above problem fit the bill too? Owner complained of 'bad feeling' above 5k. I couldn't (and neither did DeltaDash) detect any knock.

Richard

 

Just had chance to try it in higher gears and it seems ok , although the fault didnt occur every time before so I wont count my chickens just yet. All I have done is removed the ITG,cleaned out the goo from the airbox and replaced it with a 3000 mile old std filter, I'll keep you posted .

Pete, thinking about it the fault didnt occur straight after changing to the ITG, so I guess its doubtful that it was fitted wrongly, the problem started after the filter had been in for approx 2500 miles.

Cheers Steve