Evolution IX – A Solution with a little egg on my face.

The Evo is back in Jim’s garage and now runs almost as it should.  It burned out at least three tech’s before the root cause was finally revealed.

It started with severe drivability problems and a solid P0500 code in the OBDII ECU.  Running rich and not really in a drivable condition I was frustrated as I went onto All Data and followed the problem determination maps.  It appeared to be all about voltages.  The ECU was seeing the wrong voltage from the speed sensor.  I thought that the sensor must have failed, but disconnecting it left the errant voltage still on the circuit.

I enlisted the aid of another tech who’s problem determination skills are excellent.  We both followed the maps and probed and back-probed to see where the voltage was coming from.  We settled on the gauge cluster as the culprit.  We could make the high voltage disappear by disconnecting it from the circuit and it would reappear if reconnected.  So off to Mitsubishi parts to purchase a replacement I went.

After receiving it, swapping the bulbs and a couple of masks from the original I plugged it in only to have the problem solid as ever.

I had already invested countless hours and now several hundred dollars and the problem persisted like a bad cold.

With another friend’s help and his roll-back we brought the car to the dealership to see what magic they could whip up.

A couple of days later they were 97% certain it was the ECU itself.  I told them to go ahead and order up another one and waited.  A week went by as the ECU was still in process.  My VIN had to be flashed to it and it was caught up in shipping delays. 

Finally I got the call from Mitsubishi.  The ECU wasn’t the cause.  More time was spent by the tech to try to track down the source.  It appeared to be in the area of the MAF (mass air flow).  A replacement was ordered.  Again, more time was spent waiting for it to be shipped.  After several days and its arrival it failed to resolve the problem.

That tech was burned out and I don’t blame him.  The problem had certainly burned me out.

The dealership put their shop foreman on the problem.  He and I discussed how the problem manifested itself and what approach I had taken.  He agreed it was a tough one, but felt confident he would be able to resolve it.  He wrestled with it for several days.  Tracing down wiring and checking voltages without being able to pin point anything meaningful.

Then he found a known good Evo and did a complete scan of all systems.  He did the same with my car and found only one discrepancy.  It was at the MAF that a reading was not as it should have been.  He continued to search around the intake area when he put his hand on the outlet hose of the intercooler and felt a gap at the hose.  Visually it looked fine and the t-bolt clamps were in perfect shape, but there was a leak that when he fix it, all was again right with the Evo. 

I have driven turbocharged cars enough to recognize when a hose has blown off.  Always a big pop and then no power as the car becomes naturally aspirated with low compression.  This was different enough that I failed to realize what had happened.

With the integrity of the intake’s pressure side restored that car was happy again.  The boost would easily reach 1.5 bar and was no longer running rich.

I still needed to work out a better connector hose arrangement, but I also had to deal with the consequences of the car running far too rich for far too long.  Both the O2 sensors now would not heat up properly and would need to be replaced and a new high flow cat was also put on order.

It will be just a little bit longer before the Evo is back in tip top shape, but not that long.

This has been and expensive, but valuable lesson.