Surging Power At 4500+ Rpm

[nick280]

Hello,

I've been helping a friend out with his Impreza turbo as it had the usual oil leak on the rhs rocker cover and he wanted it looked over before he did a track day in it. The car is a 1996 WRX but has had a Legacy engine fitted at some point but the TD05 has been retained luckily. Only modifications are an HKS cat back exhaust and an Apexi cone filter (plus what I've fitted as I'll explain).

The car had recently had an oil change so I didn't do that but I did fit new PFR7B plugs and a blue print fuel filter as part of the check over.

The car had a boost issue when he brought it to me which I put it down to the 3 port solenoid valve on the inner wing as it would occasionally boost nicely at 1bar but more often at 0.5bar. So I ordered a dawes device MBC, fit it and set it to 0.7bar as the car is quite old and done 150k (no idea about the engine) so I'm playing safe.

After this, I went for a spin and it was hesitating at over 3k rpm but boost is holding solid. I didn't think I'd have noticed this before due to the unstable boost and with it normally only having 0.5bar. The car didn't have a fuel filter when it arrived so I thought I'd get the injectors checked. They came back Ok so I refitted them tonight. I noticed that the air mass sensor had a thin film of oil on it so I clean it by spraying brake cleaner on and all around the inside and gently blew it dry with the air line. Put it all back together and it is better but still holds back at 4500+ rpm. Again, boost hold solid and it's not a violent hesitation like a miss fire (although it might be) and I'm still thinking it's fueling. I think the reason for the initial boost problem might have been due to another problem and the car was cutting boost itself in a safe mode way. It also crossed my mind it might be an ignition timing cut back too. I did try flooring it in second to see what it did as I came back from a test run and the car pulled nice and strong but at 5krpm just seemed to run out of power. Power tailed off fast to near nothing at 6krpm

I don't really want to spend much more money as a trial and error process so I'm asking here for any help/suggestions or knowledge that could be shared before I give it back to him without fixing the car.

Thanks in advance for any help.

Edited June 3, 2013 by Nick280

[scooby sid]

I'm having a problem that sounds the same myself so i would love to hear if anyone can help.

[lewisscoob]

Are MBC's not supposed to be mapped in?

Personally I would have investigated the standard boost control before throwing in another variable.

[nick280]

I wouldn't have thought what I've done with the MBC would have made a great deal of difference? Setting boost upto standard doesn't alter anything. Running the car at 0.5bar (actuator pressure) makes it a lot less noticeable but it is still there.

I've asked my mate to take it to somebody who can test the air mass meter as I'm leaning that way at the moment unless somebody has any ideas?

If we find anything out, I'll post it up.

[scoobywho]

Is it the vtec kicking in?

[g1983]

Is it the vtec kicking in?

That wouldn't be a surge, that would be similar to batman flicking the afterburner switch on the bat mobile

[scoobywho]

Hahaha

[g1983]

That wouldn't be a surge, that would be similar to batman flicking the afterburner switch on the bat mobile

Or the modern equivalent, scoobywho's hawk....

[scoobywho]

Lol have I not got a vtec hawkeye its bloody rapid after 6500 rpm