Hi:
Like yourself, Scotty, I own and love my 2006 Toyota Matrix. Occasionally on cold starts, the engine rattles for awhile. I have previously read that the noise comes from valves in need of adjusting and is better left alone, but recently have seen videos warning about the VVT system needing work to prevent a cam lockup (?).
What's happening and does the engine require immediate attention?
Thanks for your time and attention. Yours is a welcome voice of common sense and practicality.
My Best, Dave
This is a known problem with this engine, very brief grinding on cold start at cold temperatures. Usually caused by wear in the VVTI system. Here's the Technical Service Bulletin and a ToyotaNation Forum link on it.
https://www.toyotanation.com/threads/tsb-engine-knock-rattle-squeak-on-cold-start.301528/
https://www.tsbsearch.com/Toyota/T-SB-0087-09
(This is info that I looked up for my 09 Matrix, with the same engine. I imagine it applies to an 06 )
What's happening and does the engine require immediate attention?AND
I spoke to an experienced mechanic about occasional Matrix startup rattling. He told me the usual fix (which he has done an number of times) is to replace the vvt solenoid, which is readily accessible from outside the engine, easy to swap and relatively inexpensive.
A bad VVT solenoid creates poor lubrication and should be replaced. If the oil pathway is restricted in any way (clogged screen/solenoid) at the solenoid you will get the startup rattle sound.
Try cleaning the screen and solenoid. You can use a basic multimeter to test the solenoid to ensure it works properly as shown in the following video here . This is a DIY friendly task.. If the solenoid is functioning correctly you could have a more serious issue, as AMD explains here which can quickly become costly.
I spoke to an experienced mechanic about occasional Matrix startup rattling. He told me the usual fix (which he has done an number of times) is to replace the vvt solenoid, which is readily accessible from outside the engine, easy to swap and relatively inexpensive.
@dschind did that resolve your trouble?