After 10 mins of driving, 1999 WRX loses power and coughs black smoke

[chrislaya]

Hi guys, newbie here. I bought a 1999 WRX less than a month ago. It is stock, has no modifications and has 128,000km on the clock. Guy I bought it from said it only run 400km in the previous year and was always garaged. Test drive was OK.

First thing I've done when I got the car was to replace the oil and genuine Subaru oil filter, spark plugs and fuel pump. I only use 98 octane and mindful of warming up the engine and waiting 2-3 minutes when shutting down the engine.

After having the car for a week, I noticed that after driving it for 10-20 minutes (the issue is intermittent), when I am coming off from stop (e.g. traffic light) the car coughs black smoke and loses power and stutters. This happens especially if it is going uphill. I have to rev it really hard just to "get it over the hump" and the smoke disappears. The problem happens in the 1st and 2nd gear and disappears on the 3rd and 4th gear. Then it will happen again in the next stop/traffic light. I am also mindful of the rev and only go to 3,000-4,000.

Having said that, the car is great in the first 10-20 mins and I can feel the turbo working.

These symptoms also appears on this thread but unfortunately the OP didn't come back with his findings. http://www.igotasubaru.com/showthrea...9023#post19023

My Google search for similar symptoms suggested replacing the O2 sensor, check for compression/boost leaks, excessive fuel pressure (bad fuel pressure regulator or plugged return line), leaky fuel injectors, dirty air filter or restricted air inlet, or a defective coolant sensor that prevents the engine management system from going into closed loop mode.

I am now apprehensive to drive it for long drives until this issue is solved. I am also anxious that I got a bad car and hopefully it's not expensive to fix.

Thanks in advance for your help guys!