300,301,303,305 fixed on Avalon 1MZ-FE

[tacosteelersman]

My parents 96 Avalon 1MZ-FE waste spark system (NON VVT)came down with the dreaded 300,301,303,305 misfires. We decided to give the Avy a major tune up, it has around 188,000 and leaking valve covers. The tune included complete timing belt job, complete valve cover gasket job, including valve check, thermostat,fuel filter,air filter,and complete intake cleaning. The problem was the rear bank towards the firewall was misfiring on all cylinders, when we removed the timing belt covers the issue became clear. THE REAR CAM JUMPED A TOOTH OR TWO CAUSING THE MISFIRE CONDITION, WITH THE CRANK LINED UP AND FRONT CAM LINED UP IN THE PROPER POSITION THE REAR CAM WAS ADVANCED. All new parts were installed and timing corrected, now the Avalon is running just like new. I wanted to share my findings with TN, I have gotten so much here the least I could do is try to help other TNers.

[73sport]

Originally Posted by tacosteelersman

My parents 96 Avalon 1MZ-FE waste spark system (NON VVT)came down with the dreaded 300,301,303,305 misfires. We decided to give the Avy a major tune up, it has around 188,000 and leaking valve covers. The tune included complete timing belt job, complete valve cover gasket job, including valve check, thermostat,fuel filter,air filter,and complete intake cleaning. The problem was the rear bank towards the firewall was misfiring on all cylinders, when we removed the timing belt covers the issue became clear. THE REAR CAM JUMPED A TOOTH OR TWO CAUSING THE MISFIRE CONDITION, WITH THE CRANK LINED UP AND FRONT CAM LINED UP IN THE PROPER POSITION THE REAR CAM WAS ADVANCED. All new parts were installed and timing corrected, now the Avalon is running just like new. I wanted to share my findings with TN, I have gotten so much here the least I could do is try to help other TNers.

Interesting - as that would not have been my first guess. . . .Then again, i doubt it was your's either. . . Good eye and way to be thorough!

It's alive!

[tacosteelersman]

Correction. My first post said timing advance, it was a timing retard. No that was not my first guess, but the timing jump was the only indication of wrong doing. There was more work performed at the time like bypass pipe, injector cleaning and gromets, power steering pump, also additional washers used on valve cover bolts, all electrical connections got Dielectrtic grease, and all threads got neversiezed, red coolent,new PCV. Im sure im missing some.