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1991 Corvette ZR-1 · 10-07-2022

have had some spirited drives in the Z and noticed I get a decent puff of smoke on an aggressive downshift sometimes. Any other time, no smoke even on WOT without downshifts. Well after a few romps to near redline on one trip and off throttle coasting down to a stop at a light, I noticed the engine was running rough. This was after I looked in my rear view mirror around 4K rpm during the off throttle deceleration and saw a big puff of oil smoke. Not constant, just a decent quick cloud almost like the engine took a teaspoon gulp of oil in the cylinders. Pulled into a parking lot and the car recovered from the rough idle. The first thing that popped in my mind was O2s or spark plugs got saturated with burned oil and this caused the rough running condition.

I have had a few more trips to the 6-7K rpm area since and no issues but I also didn?t get off the throttle completely on those for decel. Looking inside the plenum and it is the usual shiny wet appearance that is what we have come to expect from the LT5. Driver side PCV valve is new while the extremely rare passenger side valve is still the original. Both valves rattle freely. There was noticeable oil volume collected below the pcv valves when removed. As expected, the tips on the Corsa are black after a few drives. So I am going to try a catch can and see if this provides something of value.

This always felt like an LS band aid and the idea of one is not great to me. However, the idea I may be slowly strangling spark plugs or O2 readings with burning oil also does not sound great either. Did a compression check a few years ago and all cylinders were great. Also, I am wondering if the after fires I sometimes get on decel are due to oil smoke in the exhausts messing with the O2s and making them enrich the combusion.

Anyway, the can I went with was an ADD W1. They come in lots of colors but I went with black to try and not draw the eye to it versus some bright purple or blue. The internal baffle design looks good and there is no Brillo pad style filter. Even has a little dipstick to check how much oil is in it if needed. I guess I will see how this works out and follow up with results good or non eventful.

Also as a side note, Dorman makes a hood prop clip assortment with a decent replacement for the passenger side fuel vapor hard line retainer if you need a new one. Stumbled on it while at the parts store for pcv hose. Dorman 45396

10-07-2022	#1
1991 Corvette ZR-1 Join Date: Sep 2018 Location: Florida Posts: 294	Reluctantly joining the catch can club have had some spirited drives in the Z and noticed I get a decent puff of smoke on an aggressive downshift sometimes. Any other time, no smoke even on WOT without downshifts. Well after a few romps to near redline on one trip and off throttle coasting down to a stop at a light, I noticed the engine was running rough. This was after I looked in my rear view mirror around 4K rpm during the off throttle deceleration and saw a big puff of oil smoke. Not constant, just a decent quick cloud almost like the engine took a teaspoon gulp of oil in the cylinders. Pulled into a parking lot and the car recovered from the rough idle. The first thing that popped in my mind was O2s or spark plugs got saturated with burned oil and this caused the rough running condition. I have had a few more trips to the 6-7K rpm area since and no issues but I also didn?t get off the throttle completely on those for decel. Looking inside the plenum and it is the usual shiny wet appearance that is what we have come to expect from the LT5. Driver side PCV valve is new while the extremely rare passenger side valve is still the original. Both valves rattle freely. There was noticeable oil volume collected below the pcv valves when removed. As expected, the tips on the Corsa are black after a few drives. So I am going to try a catch can and see if this provides something of value. This always felt like an LS band aid and the idea of one is not great to me. However, the idea I may be slowly strangling spark plugs or O2 readings with burning oil also does not sound great either. Did a compression check a few years ago and all cylinders were great. Also, I am wondering if the after fires I sometimes get on decel are due to oil smoke in the exhausts messing with the O2s and making them enrich the combusion. Anyway, the can I went with was an ADD W1. They come in lots of colors but I went with black to try and not draw the eye to it versus some bright purple or blue. The internal baffle design looks good and there is no Brillo pad style filter. Even has a little dipstick to check how much oil is in it if needed. I guess I will see how this works out and follow up with results good or non eventful. Also as a side note, Dorman makes a hood prop clip assortment with a decent replacement for the passenger side fuel vapor hard line retainer if you need a new one. Stumbled on it while at the parts store for pcv hose. Dorman 45396 Last edited by 1991 Corvette ZR-1; 02-22-2024 at 10:04 PM.