Check engine light is on, loosing power and starts shaking intermittently on 2004 Toyota Corolla

Check engine light first started coming on/off since 4 years ago strictly in winter. Turns off itself for long period in summer. Next winter is back on. Last year after long (1 week) stay with no driving (in winter again), after starting the engine, felt like it's running on 3 cylinders instead of 4. Took to mechanic, replaced 1 ignition coil - that fixed the problem, restored car power, check engine light shut off (may be due to codes erased) then come back on in 3 weeks and stayed on for the entire summer (never happened before), but no performance problems. Now, light is on, intermittently shaking (like running on 3 cylinders). Replaced O2 sensor (as suggested by diagnostic code). 1 week ran with no problem and no light. Now problem back again (intermittent power loss, light is on). Multiple (5) codes show ALL 4 IGNITION COILS PRIMARY/SECONDARY circuit slow response, and O2 sensor slow response (sensor itself was replaced last week). Mechanic said will look into it but seems like does not have enough experience with this kind of problem. Any suggestions? Thank you!

by in Buffalo, NY on February 04, 2013
2 answers
ANSWER by on February 05, 2013
Get your exhaust flow checked for a possible fouled catalytic converter. If pressure is low and temp is high, you are getting backpressure to the engine from the exhaust. This will trip O2 sensors and choke the engine causing a read of all 4 cylinders misfiring.
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ANSWER by on February 05, 2013
SEEK A 2ND OPINION OR SCAN CODES AND POST SO WE CAN ADV
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