It's like Magic

[artbuc]

RE: 99 Avalon 3.0 V6 w/83k miles

When I turned off the car, the engine stopped with a little shudder. Has been doing that for a long time. After replacing timing belt, idler pulleys and water pump, engine shudder disappeared. When I turn off the ignition, engine now dies smoothly and quietly.

Can anyone explain this?

[artbuc]

Originally Posted by artbuc

RE: 99 Avalon 3.0 V6 w/83k miles

When I turned off the car, the engine stopped with a little shudder. Has been doing that for a long time. After replacing timing belt, idler pulleys and water pump, engine shudder disappeared. When I turn off the ignition, engine now dies smoothly and quietly.

Can anyone explain this?

In addition to eliminating shutdown shudder, my car runs much better on the highway.

I just spent an hour reading Google info on timing belt stretch. Very controversial with some saying timing belts ABSOLUTELY DO NOT stretch while others say they do stretch enough to retard timing and affect engine performance. One person actually said Toyota had a history of timing belt stretch problems but did not give any reference to back-up his claim.

Since I did not check timing before, I can not prove anything; but, I'm convinced that the new timing belt noticeably improved engine performance, for whatever reason.

[RIP]

Timing is a critical element in a smooth running engine. It insures the valves open and close in sync with the rise and fail of the pistons. If the timing is slightly off, fuel can be exploding within a cylinder and/or the exhaust not quite expelled, as you shut down. These forces are pushing on heavy pistons and cranshafts. The momentum of this weight moving at shut down creates your shudder. Here's a little back ground info: http://www.carbibles.com/fuel_engine_bible.html There are 3 pages.

[artbuc]

Originally Posted by RIP

Timing is a critical element in a smooth running engine. It insures the valves open and close in sync with the rise and fail of the pistons. If the timing is slightly off, fuel can be exploding within a cylinder and/or the exhaust not quite expelled, as you shut down. These forces are pushing on heavy pistons and cranshafts. The momentum of this weight moving at shut down creates your shudder. Here's a little back ground info: http://www.carbibles.com/fuel_engine_bible.html There are 3 pages.

Thanks RIP. Do you think the old timing belt could have stretched enough to change the timing? I have another theory: Even if the belt didn't stretch, it could have become thinner. The thickness of a timing belt is critical. Gates told me they actually sand the back of the belt to make sure it is exactly right. The old water pump hub had little blobs of rubber deposit on it. Also, the old belt came off easily whereas the new belt had a tight fit over the LH Timing Pulley. Whether the old belt stretched or became thinner or both, the engine timing was definitely being adversely affected.