R32 Gtr - Full Boost, No Power

[BigRed09]

Hello everyone

I am having a small problem with my 32, sometimes it develops a problem where there is no power (it struggles to get up hills) but it is developing full boost very quickly, perhaps more so then usual. It has happened 3 times now over the past few weeks, but normally if I leave the car for a while it comes good again.

Once it just developed while I was driving, the other two times, it has been problematic from startup. One of these two times, I restarted the car and all was good after that. The other time, restarting had no effect.

I have noticed that when it is having this problem it idles lower then usual and idle sits on -16 to -19 or so mmHg of vacuum

It also sounds very strange when it has this problem when on throttle.

I have been over all the intake piping both manually and doing a boost leak test with a compressor and done a compression test on the motor, and all is healthy. There is no oil in the coolant either. When the motor runs without the problem it runs very smoothly and vacuum is normal, -20/21 mmHg.

I am beginning to suspect the cat despite it being fairly new, however if that was the case the problem would not be intermittent would it? Also, my front turbo recently rattled off one of its bolts holding the dump pipe on, the one closest to the block and i am unable to get another one on there without taking the turbos off. Could it be a blown exhaust gasket? I will have to take the dumps (and therefore turbos) off to check.

Car has R34 N1 turbos and HKS dumps and a PowerFC. The car feels more or less normal when in lower RPM, but as soon as it gets past about 3.5 the power hits a massive flat spot which continues for the rest of the RPM range.

I am at witts end to try and diagnose this problem. Any suggestions will be followed up and appreciated greatly. Thank you

Edited May 9, 2009 by BigRed09

[BigRed09]

For future searches it appears that the cat converter is broken. The problem is becoming more frequent now and there is now a small rattle coming from the cat converter which can be stopped by applying pressure. This is probably what is causing the exhaust note to sound very retarded. If there was a massive congestion in the exhaust it would also explain the low vacuum as the motor is struggling against this congestion. This would also make sense for the fast boost spoolup as the motor is drawing far less air and the turbos have to work much less to compress the entire system.

It is somewhat disappointing that noone offered any opinions, but it was a somewhat complicated problem and my explanation was not terribly good.

[drgtr7]

Thanks for your info mate - helped me out heaps

[Rolls]

If it isn't the cat (most likely answer) having heavily retarded timing does the same thing, louder exhaust, low power, boost comes on way earlier etc.