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2014 Hybrid Avalon starts up with a choopy/ROugh engine

EaglewingmdEaglewingmd Member Posts: 2
edited December 2022 in Toyota
I have a 2014 Toyota Avalon Hybrid. With a cold engine the engine starts up and runs choppy, or tough, as if there is a misfire. One time I got a code which said that cylinder 4 was misfiring. I have investigated possible caseus and replaced all spark plugs. Same problem. The checked the coils and the misfire code did not move to another cyliinder. And I have replaced the Camshaft sensor. Nothing fixes it.
This happens with a cold engine, but it also happens at a stop light on start up, after and then the engine shuts down.
Although it doesn't happen 100% it's frequency is increasing. It is close to 80% of start ups.
Any suggestions?


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    thecardoc3thecardoc3 Member Posts: 5,768
    Nothing that you have done so far has solved the start-up misfire, what you haven't done however is test and try to prove what the cause is. That however is easier said than done since it appears based on the description above that it probably goes away after the engine has run for some varying of time after a start-up.

    The fact that this misfires and shuts down on a restart (Stop-Start System?) would help to recreate the conditions and make it "easier" for a technician to set up testing to solve this.

    If you are looking for a "Silver Bullet" type answer which amounts to a guess IMO, a leaking fuel injector could do this. Any computer input responsible for correct ignition timing calculation could play a role. A wiring or control issue for the coil in the affected cylinder(s) could also cause these kinds of symptoms. This is why testing is so important, you could guess and take a shot at any one of these and maybe solve the problem or more than likely fail to do so.
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