Hi,

I have this issue since the end of winter with my 1998 D1 v8 (GEMS). With heavy rain or when I pressure wash the truck the engine dies and stays stranded until the engine bay has dried out. If I try to restart it just misfires and backfires in the intake and ends up just doing nothing, kind of like when the plug wires are too old (but this is not the case). I had the truck towed back home three times and the only way to get it to start and run well again is to let it in the garage overnight with a heater under the hood. I've checked underhood plugs and grounds and I opened une ECU box to blow air in it and make sure it's dry, but only time, air and heat does it. The problem doesn't come from the coil packs neither as I switched them and it doesn't do any difference. Also, when the problem occurs, the check engine light flashes and relays and actuators controlled by the ECU flickers (AC fan, EVAP solenoid, etc). The problem seems to come from the power or the ground circuit for the ECU... Has this problem ever happened to another forum member and if so does any of you have a clue of where to look next? Common gremlin?

Thanks!

 

the ecu is stratigicly located on the passenger side fender well ....to absorb moisture from all directions as well as through a rust hole that may have secretly formed in the fender well and caused the ecu to corrode....outside AND inside....unhook the battery, remove the ecu....put it on a bench or table where you can work....take the covers off and have a look inside......mine was half full of a slimy alluminum corrosion paste.....that can cause all kinds of hell to happen....I lost spark in a snowstorm....it's worth a look

 

Like I said in the first port I HAVE opened the ECU to clean it up and the problem didn't come from there. There was no rust, no holes in the covers, just a bit of corrosion on the mosfet legs due to condensation as the box isn't waterproof at all like you said. I removed that corrosion which might have become somewhat conductive if moist and electrolyte was on it. I used a toothbrush and compressed air.The truck still has the problem and it is outside the ECU, like it's losing its power or its ground...

 

When one sensor becomes water shorted they all do since they share a common ECU ground. Up to you to find which one is taking water in. You can stave off some water ingress by using dielectric grease in the connections.

 

This is normal that sensors share the same ground, it is always like that, but the ECU still can detect which one is shorted by reading a non-probable return resistance or current. And a shorted sensor doesn't cause the ECU to lose power. According to the diagram I must better be looking at Fuse #3 in satellite fuse box 1, connector c216 next to the accelerator pedal (lhd models) and splice 292 in connector hj7 under the glove box but it' all inside the cabin... So I guess I'll be more likely to find a bad wire in the engine management harness and have to route a new white/green ECU feed wire. The dealer would probably just replace the engine harness if still available... there's also the ground stuff, everything goes by ground E100 behind battery but I checked it also, meaning it's still a case of rotten wiring... That's the reason why I asked here to see if this was a common problem with a known fix so I'm not just tearing the whole harnesses to inspect every centimeter of every wire... It's gonna be a long day!

 

It's not specifically a common problem, if it was this would be a bicycle forum. What I did with mine was dielectric grease the ECU connector because I had found light corrosion. Same with the fuel pump relay on the passenger inner fender, the cut-off relay and all the relays inside the cabin in both footwells. I kinda had the same problem once upon a time, my truck sits outside in all kinds of weather 24/7/365 and has now for the last eight years. Nothing funky has happened since I did that. Behind the kick panels in the footwells I found the floor seam had rotted throwing water off the tires directly at the relays. The large grounds get copper anti-seized at least once a year. I also use LPS to help shed water at every sensor connection - like using WD40 in a dizzy cap, same same.

 

Eheh that's funny the bicycle thing... I spent some time yesterday looking for something wrong around the ECU and wiring ans everything around the right inner fender but didn't find anything special. I'll do like you and put dielectric grease by the bucket and see. I've already sealed the ECU plugs surroundings at least and I think I'll place the ECU in a bag. What do you call LPS?

 

LPS Labs

Bagging the brain box will make a nice solar still, you could lick the moisture from it when stranded in the desert. The reason it's outdoors is to help it dissipate internal heat through the case. These where made with technology that made a Pentium 133 Mhz chip running Windblows 95 appear like HAL9000.

 

Not to butt in, but maybe get a spray bottle with water and spray things one at a time to see if you can pinpoint any trouble spots. Just thinking out loud.

 

Ran through my mind too.....