New to forum I've searched around but cant find what I'm looking for my wife has a 07 mazda cx7 160,000 miles about 20,000 ago she had the dealer put a new vvt actuator in cause it was making a ticking and supposedly did a homing chain to well everything was fine for awhile than the car died one day i got it home and got it started and it did not run rite at all so i did a compression test on it and i think it was cyl #1 &#3 have no compression other to were in the 160s If I remember correctly there was no warnings or nothing never smoked ticked anything just after a long day of driving it died my question is can the vvt make that happen? Just seems weird that 2 cylinders would just go bad instantly has anyone else had this problem?

 

I would bet it is not the VVT but the friction washers. Highly recommended to replace the friction washers on both cams and crank when doing the timing chain or VVT. This engine does not use keyed notches like normal common sense engines. They use these washers that are suppose to hold the gears (VVT) in place. If they slip there goes your timing and in your case valves hitting pistons and zero compression. Sorry to be the bearer of bad news.

 

I kinda figured the motor was gone I've worked on many motors and vehicals so figured it wouldnt b a easy fix but befor I pulled the motor out and replaced or rebuilt just to find out its sumthing simple I wanted to ask around get some opinions on what it could be. Cars not in bad shape and hate to just get rid of it seeing I out tires on it 4 days prior to all this but guess it's just my luck lol

 

Other thing I dont get is it will still start shake like a bastard no power but it's still quest figured if pistons were hitting or valves were bent it would b loud it's not

 

if you have zero compression in two cylinders (that are synced together on the crank) then its the valves that are bent. I have seen engines run on two cylinders, not well but running. I bought my 2008 cx7 with a blown motor. I have pulled the engine and replaced all the broken parts. The head rebuild was $250 but I had two bent valves so it ended up being $350 Friction washers are $18 each and there are 4 of them. Its recommended to replace all cam and crank bolts too. New head gasket means new head bolts. The thing about the head is that its called a shim and bucket. There are no hydraulics or adjustments on the valves. They have to be grinned to specifications and I found out the machinist hate working on these for that reason. If you do the work yourself on the rebuild head you may be in it for at least $500 The labor can be intense due to small spaces. I am grateful mine is out of the car.