'02 LX - Misfire codes only when it rains (1 Viewer)

[tseck73]

Seeking input advice on a vexing issue with my '02 LX470 with 178K on the clock. I am getting P30x misfire codes on all cylnders, except #3, only during rain or after the car wash.

In the past 5K miles I'd done the following:

• Replaced all 8 plugs and ignition coils with OEM and Denso respectively
• Timing belt and water pump with the Aisin kit
• Doug Thorley headers and new Denso front O2 sensors

These items were done as PM, not to address the misfire issue. Addly enough the misfire issues seem to have sprouted up after the timing belt service.

The frequency is the codes is throwing me, simply becuase it seems tied only to when we have rain. I did check for leaks and may have one at the corner of the windshield on the drivers side. Are there any electronic modules down there that could trigger this? I know the ECU is behind the glove box, and that is dry...

Any insight/advice would be super helpful - thanks!

 

[tseck73]

Anyone? Bueller?

 

[2001LC]

When I hear water related electricals issue. My first thought, is water entry into cabin, and getting on/in connection points. This can be circuit to or on ECM. Water entering around/under windshield molding, is common when windshield replaced. But very uncommon. If factory windshield and molding, still on and never removed. So I'd first test for leaks, if not factory install.

Pressurizing cabin and looking for air escaping, is one method.

Looking under hood, would be a first step. But is my, second though. It's an issue we see, after timing belt or fan bracket service. All to often the crankshaft sensor and oil sending unit wire harness is routed wrongly, in front of fan bracket. Wires then very often rub on fan belt of one of it's pulleys. Wire housing, sheathing and wire are cut be the rubbing. If wire only partially cut. Water entering sheathing. May may create a temporary short circuit, between partial cut wires. Thus changing resistance, and confusing ECM.

"Second though" Since difficult for water to get to wiring in front of engine, just going through a car wash. But can happen.