Carbon deposits on all four spark plugs on the RH cylinders only? - ZR-1 Net Registry Forums

Blownrunner · 12-27-2013

91 ZR-1 with 29,000 miles. I changed my O2 sensors and noticed that the RH sensor had a powdery type coating on it and the LH sensor looked a normal gray. I cleaned the muffler exhausts a month ago also and changed the plugs when I did the O2 sensors. Today I checked and the passenger side exhaust interior, which was noticeably more powdery than the right. I pulled the plugs and the drivers/LH cylinders had plugs that looked a normal gray insulator around the center electrode. The Passenger/RH cylinders had a coat of the black powder on them evenly. The car runs strong and starts up great. The injectors are also new along with the coils.

Doing a quick search on plug fouling, it looks like I have carbon deposits, not oil because I do not think the plugs are 'wet', instead a light powder. Isn't the LT-5 basically two four cylinders side by side?
Two separate O2 sensors makes me believe that the sides of the engine are individually monitored and controlled.

Any idea what is going on here? I am thinking that an oil leak is out because it would be in one area of the engine, not all four cylinders on the RH side. Could it be running rich? Would the RH head need to be re-torqued? Is there a faulty sensor other than the O2 sensor? Maybe the grounds on the back of the heads under the plenum?

I am stumped here. Thanks.

BTW, The carbon looking deposits accumulated in the last 9 months/1,000 miles.

12-27-2013	#1
Blownrunner Join Date: Dec 2012 Location: Tampa, FL Posts: 118	Carbon deposits on all four spark plugs on the RH cylinders only? 91 ZR-1 with 29,000 miles. I changed my O2 sensors and noticed that the RH sensor had a powdery type coating on it and the LH sensor looked a normal gray. I cleaned the muffler exhausts a month ago also and changed the plugs when I did the O2 sensors. Today I checked and the passenger side exhaust interior, which was noticeably more powdery than the right. I pulled the plugs and the drivers/LH cylinders had plugs that looked a normal gray insulator around the center electrode. The Passenger/RH cylinders had a coat of the black powder on them evenly. The car runs strong and starts up great. The injectors are also new along with the coils. Doing a quick search on plug fouling, it looks like I have carbon deposits, not oil because I do not think the plugs are 'wet', instead a light powder. Isn't the LT-5 basically two four cylinders side by side? Two separate O2 sensors makes me believe that the sides of the engine are individually monitored and controlled. Any idea what is going on here? I am thinking that an oil leak is out because it would be in one area of the engine, not all four cylinders on the RH side. Could it be running rich? Would the RH head need to be re-torqued? Is there a faulty sensor other than the O2 sensor? Maybe the grounds on the back of the heads under the plenum? I am stumped here. Thanks. BTW, The carbon looking deposits accumulated in the last 9 months/1,000 miles.