New Member, Working on a cx-7

[cabey]

Hi everyone, my name is Chris and I've just joined this forum because my wifes cx-7 has had a vvt failure and Im in the process of repairing it. This forum seems to have lots of good info and I thought I might be able to pick up a few tips.

Im in the process of putting everything back together. The VVT failed and the timing chain has broken. (only 90 000 km on this vehicle) This caused damage to the chain guides and also caused the #2 piston to contact the intake valves. I removed the head and had a valve job done at a local engine rebuild shop. the piston damage was minor (luckily this happened at low speed). I checked that the piston ring still moves easily and dressed out a minor burr on the top of the piston where the valves contacted. Since the turbo was easy to get at with the head off I removed it and rebuilt it while I was waiting to get the head back. So far Ive reinstalled the turbo and will be installing the head today.

This is my wifes daily driver so I am just returning everything to stock. I will be browsing the forums for tips and how to's but feel free offer any advice!

Chris

[Aizen Sosuke]

Clean or remove the EGR while you are at it.

[cabey]

Originally Posted by Aizen Sosuke Clean or remove the EGR while you are at it.

Ive heard of lots of people removing the EGR, what is the usual problem the EGR causes? Before the timing chain snapped the car would have an engine light when cold (-20 C), the dealer could never figure out what caused it. Vehicle also had a surge or hesitation when accelerating. Im not sure if any of these symptoms were caused by the failing vvt and stretched chain but im assuming the hesitation was. I also found that the factory fuel injector seals were shot.

[Cheapspeed]

Originally Posted by cabey Ive heard of lots of people removing the EGR, what is the usual problem the EGR causes? Before the timing chain snapped the car would have an engine light when cold (-20 C), the dealer could never figure out what caused it. Vehicle also had a surge or hesitation when accelerating. Im not sure if any of these symptoms were caused by the failing vvt and stretched chain but im assuming the hesitation was. I also found that the factory fuel injector seals were shot.

I would leave the EGR on, especially for a daily. You'll get better gas mileage with it.

[cabey]

I'm in the process of replacing the vvt on the camshaft. I marked the old vvt to the cam and marked the new vvt in the same spot. When i went to crack the bolt that holds the vvt to the cam I noticed it had already loosened off on its own. It is possible that the vvt has turned so now obviously my marks are useles. The manual states to refer to timing chain assembly in the engine workshop manual. Does anyone know how to properly reindex the new vvt to the cam?

Thanks

[Ozynigma]

VVT is not indexed to the cam.

[cabey]

Hi thanks for the reply. After reinstalling the head with two new intake valves, replaced the vvt, chain guides and chain, and rebuilding the turbo the car is running again. The hesitation that was there before the vvt and chain broke is still there. I disconnected the upstream oxygen sensor per the TSB instructions and the hesistation went away and the car runs really well. I ordered a new sensor and will change it next week.

I must say that this car has had a fair amount of problems for only having 90 000 kms on it. It was maintained regularly by the dealer per the maintenance schedule from the day it drove off the lot. I wrote mazda a letter to express my frustration with the vehicle and their reply was that all of these issues were caused by regular wear and tear and improper maintenance!

In addition to the engine problems Ive also had to replace the tie rods, a rear wheel bearing, and all of the stabilizer links. The ball joints are also starting to wear. I also have an airbag light that randomly comes on. Hopefully next winter the engine light wont come on anymore when the engine is cold.

Very disappointed in this vehicle.

Chris

Also thought i would mention that the factory seals on the injectors were toast. The dealer quoted me 30 bucks a piece for injector seals which is pretty steep considering they dont last. I ended up just using 5/16 AN900 copper/asbestos crush washers that I had at work, so far so good. I got the idea from reading on this forum about guys using toyota fuel injector seals which just looked like simple crush washers.

AN900 COPPER GASKETS(CRUSH WASHERS) from Aircraft Spruce Canada

[Ozynigma]

Interesting feedback.

Mine got to 130,000km with the only major issue being two failed A/C pressure hoses. The first was replaced under warranty. The second I used an upgraded aftermarket hose.

Then I tuned it and I have had a few issues and then I ended up rebuilding the motor which has fixed all the problems. Other issues I have had were a leaking injector, leaking fuel pump screw seal and recently had the front hubs replaced. Also the transfer case had a slow leak until I swapped a resealed and upgraded transfer case in.

It sounds like yours has had a hard life for all those things to be failing at only 90k kms.

In hindsight I would get a turbo diesel if I got another SUV. A heavy vehicle with a high performance sports car motor is an interesting and fickle combination.

[cabey]

I wouldnt say the vehicle has had a hard life, it has been used as a daily driver on paved roads and rarely leaves city limits. With that being said, our northern ontario climate is hard on vehicles as well as the roads. Road salt takes its toll on the bodies and the frost heaves and potholes are hard on the driveline. Cold starting between -30 and -40 celsius also isnt easy on engines, although this car was always plugged in during those conditions. Keeping all that in mind, I have owned many other vehicles that have endured the same conditions and not had nearly as many problems. Anyways, I was lucky to have a heated garage to repair the car and appreciate the info I found on this site.