Updated: Mar 20
A customer of ours recently picked up a 2000 Corvette. This car had been modified before he bought it and it now has a cammed 6.0. He felt his car was running a little rich and needed a transmission tune. He scheduled a tune online and drove the car to our shop for his appointment.
During our Pre Tune Inspection, we noticed something wasn’t right. Next, we’ll walk you through step by step how we diagnosed this issue.
**I’d like to point out that a Pre Tune Inspection is a crucial part of the tuning process, check out the results of this inspection, which led us to dig deeper.**
As part of our pre-tune check, we get a temperature reading from the primary tube of each cylinder's exhaust port. We noticed that on the rear passenger cylinder, temperatures read lower than we would expect to see, as documented in the attachment above.
The narrow-band o2 sensors were reporting that fuel trims are ~15% off from side to side indicating a balance issue between sides of the motor.
There was also an audible cranking pattern that may suggest a weak cylinder.
We began looking for the cause. We could hear the rear passenger's cylinder's injector pulsing, and the coil was firing. Our concern at this point, was that the cylinder may be weak or damaged, and our next step to troubleshoot was to do a compression test.
The customer agreed and we began a compression test. Upon pulling that spark plug, we noticed that it was soaked in fuel.
When we performed the compression test, we observed low compression on that cylinder.
Next we removed the valve cover, revealing a broken Yella Terra rocker arm.
Now it's time to help Alex get this thing back on the road!