EVO X Timing Chain Follow Up

We previously went over the EVO x’s 4B11 timing chain stretch woes here. On a good day when everything is working correctly the ECU uses the cam position sensors along with the crank angle sensors to calculate the stretch of the timing chain. When it all works like it’s supposed to, the dash warning system shows a big triangle warning sign so you can get things checked out.

All too often this system fails the owner. We have had cars with the timing chain well within spec get various timing chain and  cam position fault codes. And even more concerning cars with stretched and worn chains that display no code at all. Following are pics of a 40k mile EVO X. This car had stock cams and the customer was complaining of a rough “cam” idle and some engine noise. When the car came in you could immediately hear the horrible noise of the timing chain flopping all over under the cover. The cams had even jumped timing (creating the cam idle lope).

Mitsubishi says this premature stretch is caused by excess carbon in the motor oil. Pretty much putting it on the owners for not changing their oil frequently enough. While this customer claimed he changed his oil every 3k to 4k miles, it was quite brown looking under the valve cover.

On this car the loose and worn chain had also damaged the cam sprockets. Unfortunately Mitsubishi only sells the cam sprocket complete with the MIVEC mechanism making this super expensive.  A a precaution we also replaced the chain guides and tensioner. The crank sprocket and oil pump chain were also damaged and replaced.