About 2 months ago I did my head gaskets. When I did the head gaskets I didn't put on new wires as the Magnecore 8mm wires I had on there were only about 8 months old. I did put in new Bosch platinum plugs. Everythings been going good, Land Rover was running great.

My Wife takes the Rover to get washed and gets an under carriage wash as well (I don't know if its related). Later that day I get the truck and then I get a P0305 code and a noticeable misfire.

I tried cleaning the MAF with MAF Sensor cleaner, no difference. I pulled #5 plug and it looked fine.

I swapped it with #3, no difference. I didn't have a spark tester so I used a timing light on #1, #3, and #5. I noticed a stutter when I was #5 so my thought was it was due to the coil. I got 2 new coils and a new set of spark plug wires. Still no difference.

I did a wet and dry compression test. I was around 120 dry on cylinder's 1,3, & 5 and I was around 140 wet on 1, 3 & 5. I didn't test the others.

I went and got a spark plug tester (like I should have from the beginning) and I'm getting fire. Using a long metal rod, I listened to the injectors on 1, 3 & 5. I could hear each one cycle although I'm not sure if fuel is coming out or not just that it is cycling. I cleaned the connectors for crankshaft position sensor. No difference.

I'm down to 3 things I think it could be:
MAF
Crankshaft Pos Sensor
Fuel Injector

Can you guys give me some input or ideas? I really don't want to throw money at it until I hit the right part.

 

Oh and I haven't lost any coolant and the oil looks fine

 

crank po sensor is rather hydrophobic, but it should return to normal shortly after the exposure, unless something was dislodged or sprated into the connectors such as road grit, oil, soap etc. id start there

 

My initial thought also. The undercarriage wash would shoot right up there. Maybe run the engine till warm with the hood up to dry it out. If it's raining where you are, maybe find a parking garage or other overhang. There are other electrical items that might be affected by too much water too as they get older, could be any of them, but CPS sounds about right for starters.

 

I pulled the CPS and it looked fine. Just to be on the safe side I cleaned the connectors with MAF cleaner but there was no crud or signs of water. Is there anyway to bench test a Hall Sensor?

Also, can a knock sensor malfunction cause a misfire? The knock sensor is pretty close to the CPS and it would be a lot more exposed to water during an under carriage bath.

 

The problem is probly moisture in a connector. I'd pull every connector I could find and dose it with brake clean.

This is exactly why I don't wash my engines.

 

Yeah, same here, like I said the wife was trying to be nice and wash the D2 for me

 

My Jaguar would hold water in the Coil Pack Wells. Misfired horribly. Once dry, would be perfect again.

 

jam some dielectric in the connector

 

Ok but what connectors? There has to be a connector (or pin) in particular that only effects cylinder #5. I'm leaning towards the fuel injector or injector connector being bad. I believe my next step is to pull the injector and swap it to see if the problem follows the injector and while I'm doing that test the connector. Unless you guys know an easier faster way to test the injector....?

My other thought is that its a worn lobe on the flywheel giving bad signal to my CPS...... or a bad CPS....or the MAF... or spiteful gremlins