Water is necessary for life but sometimes it can be the cause of death, especially when mixed with electronics. SureTrack community member mtbittinger had an Acura MDX that came in twice for running poorly, both times with a melted coil. They found that water intrusion into the ECU might be the cause. They posed the question to the community, and with the help of fellow community member Ericsautomotive and others, they were able to try and diagnose the issue and while they didn’t complete the repair the information found is useful to others.
The following Community Fix summarizes the interaction between members of the community that led to the solution.
Vehicle
2006 Acura MDX Touring 3.5L
Title
Running poorly, check engine light one, melted coil.
Complaint
Customer complains that vehicle is running very poorly and check engine light is on.
Diagnostic Steps Performed/Parts Replaced
Car came in running very poorly last week and found codes P0300, P0301, P0302, P0304 and P0305. Cleared codes and #2 P0302 came right back into system. Found melted coil and damaged spark plug tube on #2 cylinder. Replaced 6 plugs (all were kind of loose). For #2, had to remove valve cover and spark plug tube. Spark plug was almost completely out, upper porcelain was all broken. Tapped spark plug hole, threads were OK, just dirty. Installed new spark plug tube. Reassembled both valve covers and upper intake with new gaskets. We installed a new coil on #2 cylinder. Cleared the codes and ran great. Delivered Friday afternoon, all was great. Monday morning call on answering machine, running terrible again.
Found that the #2 coil failed and is actually welded itself to the spark plug tube, cannot even drive the coil from tube with hammer and punch.
After finding the repeated failure, I searched for causes and found many cases of the ECU in right kick panel getting water into it and shorting out coil circuit and over powering the coil, or coils. Anyone run into this? I have yet to look at the ECU to see if it had water in it. If water is the problem, can the ECU be dried out and be put back into use? Or is replacement necessary?
Best Answer from Community Member Ericsautomotive
Test the signal to the coil. Noid lamp works great for this test. Does the coil signal stay on or pulse ??
Cause
Finally got to checking this engine over, Coil melted as stated before, spark plug destroyed and blown out of head with only one thread left at the bottom. All plugs were tight. Removed all plugs and checked compression. Cylinder number 2 has zero (able to get compression tester to grab the one thread, and cannot even feel any air when cranking). The other five cylinders have 130 to 150 psi. Customer decided to replace engine. Possible water intrusion into ECU causing coil meltdown.
Correction
Replace engine and resolve any water intrusion issue into ECU.