Jason B.

I'm only asking the following to better educate myself, I will be doing a K20a2 swap in about a month and these problems will be a thing of the past but I would still like to know some possible reasons.

Vehicle is a 97 dx with Y7 motor.

This all started a few years ago when my OEM cat decided to go, I replaced it with an eBay system trying to save some money but learned the hard way on why that was a poor choice. Fast forward to today and I have built my own custom exhause of 2.5in stainless pipe, Magnaflow cat, vibrant resonator and vibrant muffler.

My problem, from the very first moment the exhaust had issues I noticed a very rich smell from the exhaust which got worse with the eBay system and all attempts at O2 spacers or later adding a cat seemed to do almost nothing to correct it. The exhaust blows a lot of black soot too, enough to turn the bumper black after one time of aggressive driving or a week of regular driving. It will even "spit" some carbon out of the exhaust at idle leaving black spots on the ground. My brother says it looks like a diesel truck when he is following me and I'm full throttle. Oil consumption averages 500ml a week sometimes more, sometimes that much in a single day.

This excess of fuel and carbon has burned up 2 cats, 2 resonators and 3 mufflers in short order, 6 months is about all I get. What I don't understand is why it's such an issue, I tried giving myself a complete exhaust system with quality components and still no love. I've read about soaking the cylinders and have done so with seafoam but still nothing.

Valve seals?
Piston rings?
Incorrect exhause without tune?
All of the above?

mk378

Fundamentally making black smoke means that too much fuel is going into the engine. Burning oil makes a gray smoke that generally doesn't mess up cats. Could be too much pressure in the fuel rail (bad regulator, compensator vacuum hose not hooked up, obstructed return line to the tank) or a sensor problem. Are any codes thrown? take spark plugs out and see if one is badly fouled compared to the others, if so that cylinder may have a leaky injector.

Jason B.

Only codes are for the cat, I switched from Bosh to Denso O2's and popped a code within a week. This is only within the past month though, for the past 1-2 years I've been running the Bosh with cat and never had a code. Although, that's probably an issue in itself thinking about it now...

I spoke with my brother again and he said I am pushing blue smoke too.

Plugs and O2's have the same issue, heavy on the carbon build-up. It can easily be washed or brushed away with minimal effort but is back after a short drive.

Compression test was performed about 6 weeks ago and had some low numbers, low of about 120 and high of about 135.

Personally, I think the motor is just at its rebuild point and needs new rings but I've also read some crazyness that says the oil rings rarely go bad on these motors.

P.S. All brake and fuel lines are new OEM, mine were rusted pretty bad and I decided to replace everything. Most everything on this car is new except the motor and fuel tank.