tcaliendo

just installed a new downstream o2 sensor and 4 ignition coils. Now my check engine light flashes then goes off and then will randomly appear again flashing then disappears again, can anyone guess what's going on?

Shaozhou Zhang

Can you provide us with the code please? A flashing CEL always means misfire but we need to know whether it's P0300, P0301 or P0302.
Downstream o2 sensor won't cause that as it only determines the catalytic converter's efficiency.
As for the coil, you might want to pull them and reinstall them.

Check this out if you haven't
https://www.rx8club.com/series-i-tec...t-here-222280/

Loki

iTrader: (1)

Are the coils connected to the right spark plugs?
Was the O2 sensor replaced because of a P0420 code? Because that's often the cat clogging, not the sensor. Clogged cat causes misfires followed by destroyed engine. So... I'd stop driving until you can confirm the cat is intact internally.

tcaliendo

Appreciate your response, here's a little more info, the car is an automatic 2006 RX8, I replaced the downstream o2 sensor because initially the check engine light came on and stayed on steady no flashing. The code indicated it was the sensor. 4 years ago I had a new set of ignition wires installed and the 4 ignition coils because of rough idling and a loss of power on exceleration. I only put 13K miles on the car in the past 4 years. If the engine is misfiring how come the flashing check engine light doesn't come on when the car is in neutral even if I rev the engine to 5K , it seems to only only come on when the engine is shifting gears and then it goes off it doesn't stay on constantly.
Once again I appreciate your input

CaymanRotary

It's definitely something in your ignition system or cat that is going bad. The check engine light never flashes unless its misfiring. What codes are you getting specifically?

Loki

iTrader: (1)

The engine is not doing any work when you rev in neutral so it's not under nearly the same conditions as when driving. The fact that it doesn't misfire in neutral is further confirmation that this is a cat issue.

Flashing CEL is ALWAYS a misfire. That's the only meaning it has.
Based on the information provided, it seems more and more likely that the cat needs replacing rather than the sensor in the cat.

tcaliendo

the code is 0300, any advice?

CaymanRotary

P0300 is a random misfire code. You'll need to check plugs, wires and coils. If these are ok next on the list is a vacuum leak or faulty injectors, or fuel pressure issues. Good luck!

Loki

iTrader: (1)

Same as above, check your cat.

tcaliendo

thanks for your help, checked wires, wire on cylinder #1 was not fully connected, secured it, cleared the check engine light, now all is well, engine running great,
happy holidays

CaymanRotary

Excellent! Glad it's back to good. Happy holidays to you as well.

tcaliendo

thanks for your input, problem was wire to cylinder#1 wasn't seated 100%, corrected problem and cleared the check engine light now engine is running great
Once again thank you

Happy Holidays

TullioRX8

Hi Rotaryarians,
my dilemma is as follows:
my engine developed a misfire suddenly so I parked it and after 2 months decided to find out what really happened. I opened the engine and found collapsed apex seals on one of the rotors. Everything else was ok.
Shelved that headache for another 3 months till I managed to save up for another complete engine straight from japan.
After fitting new engine, I noticed the CEL does not come on at all on key ON position. Engine also does not start but cranks. Fuel pressure is ok but doesn’t seem to be spark on plug leads.
Got a guy with diagnosis machine and he says he can’t find anything wrong with since he is able to read ECU.
Please help with anything I can go by.
🤷🏼‍♂️☹️