Cylinder 3 Misfire after Washing Truck with very rough idling.

[JayP_1500]

Hello all -

Yesterday I washed my 2019 Ram 1500 Laramie after it inadvertently got covered in sawdust. I drove the truck before cleaning it and it was completely fine. I used a lot of water to remove the sawdust, but nothing extreme and not directly to the engine bay (hood was closed).

I went to start it up to go somewhere and it was rough idling and I could feel a serious vibration just sitting in my driveway. It felt like an engine mount just magically disappeared and the engine was unsecured. I drove it down the road and the check light would flash and go out. I also noticed it would Rev higher (I assume to try and get to speed with a misfiring cylinder). I took it home and sat it for the night.

Today the check engine light persisted instead of flashing. I bought a code reader and it read "cyl 3 misfire (P0303)". I tried to reseat the connector for that cylinder as best I could, but it's stuck under the wiring harness. Now, if I am correct and cylinder 3 is second on the right when looking at the engine, that connector is right under the windshield where water certainly could have run down onto it. I don't want to break the connector or wires going into it, so I stopped messing with it.

I cleared the codes, and now the check engine light is gone, but the rough idling persists. I noticed when I Rev the engine to around 1100 RPM, the idling is smooth, but as soon as I let my foot off of the gas it comes back again. I drove it 50ft and the check again light is back on.

Any ideas what could be going on here? I literally just paid this off and am now dealing with this issue. My truck barely had 30K miles on it.

 

[JayP_1500]

Update: I decided to swap coil packs with cylinder 2 to see if anything changed. My ODB2 reader was monitoring cylinder 3 and was still misfiring. I'm assuming this is something specific to cylinder 3 now, like a bad spark plug?

 

[dajogejr]

Or a bad connector for cyl 3. Can you reset the code and drive it? I can’t see a spark plug going bad from a wash. I can’t see a bad connector, wire, etc., related to that cylinder.

 

[JayP_1500]

Or a bad connector for cyl 3. Can you reset the code and drive it? I can’t see a spark plug going bad from a wash. I can’t see a bad connector, wire, etc., related to that cylinder.

So I did reset the code and drove it, but it came back on quickly. I also swapped coil packs with another cylinder and the problem persists in cylinder 3. I was going to attempt to change the plugs next.

 

[kapinallinen2]

So I did reset the code and drove it, but it came back on quickly. I also swapped coil packs with another cylinder and the problem persists in cylinder 3. I was going to attempt to change the plugs next.

I doubt that the plugs are causing it. Water got into something electrical, what? a good question. Give it overnight to dry out, see if it will clear out.

 

[JayP_1500]

I doubt that the plugs are causing it. Water got into something electrical, what? a good question. Give it overnight to dry out, see if it will clear out.

It's been about 24 hours since the truck was washed and I have idled it a decent amount. I'd hope the water would have dried up by now.

The cylinder 3 coil connector is for sure try, but is there another sensor that could be wet?

 

[kapinallinen2]

It's been about 24 hours since the truck was washed and I have idled it a decent amount. I'd hope the water would have dried up by now.

The cylinder 3 coil connector is for sure try, but is there another sensor that could be wet?

How is your RF hub doing, did it get wet from a leaking rear window frame?
This is a long shot of course, have not seen any posts in prior years with your specific problem caused by washing. Plenty other misfire cases caused by marginal fuel to bad injectors.

 

[JayP_1500]

How is your RF hub doing, did it get wet from a leaking rear window frame?
This is a long shot of course, have not seen any posts in prior years with your specific problem.

Ironically that happened to me a few years ago, but the truck wouldn't start then. Dealer found cracks in the window frame and a wet module. Replaced the window and hub and haven't had a problem since.

The truck starts fine now, just has the cylinder misfire. Sitting in it now just idling and monitoring misfires. Been running about 5 mins and have 1631 misfires and counting on cylinder 3.

 

[kapinallinen2]

Ironically that happened to me a few years ago, but the truck wouldn't start then. Dealer found cracks in the window frame and a wet module. Replaced the window and hub and haven't had a problem since.

The truck starts fine now, just has the cylinder misfire. Sitting in it now just idling and monitoring misfires. Been running about 5 mins and have 1631 misfires and counting on cylinder 3.

We have two plugs per cylinder, really doubt that both are failing at the same time. Can not remember if ALFA OBD does live injector monitoring or not, that would be my next step.

 

[RiffWrath]

When all else fails. I disconnect the battery. Could be a resister is stuck or possibly a mega fuse?
Pull neg cable and let sit for a few hours possibly.

 

[Rebob0510]

What kind of air cleaner? Stock, aftermarket oiled? I had a similar issue on my truck (except is was cyl 2) I bought 2 new plugs, swapped the coil packs from cyl 2/4 but still had the cyl 2 misfire and a sometimes rough idle. I have a AFE cold air intake with oiled filter and I found the IAC (intake air charge temp sensor) was pretty dirty looking on the air inlet side and was a nice blue color on the backside. Bought a new one for $26 and haven't had the misfire code or rough idle in about a month or so. Its a quick easy cheap thing to change to see if it helps your issue also

 

[JayP_1500]

What kind of air cleaner? Stock, aftermarket oiled? I had a similar issue on my truck (except is was cyl 2) I bought 2 new plugs, swapped the coil packs from cyl 2/4 but still had the cyl 2 misfire and a sometimes rough idle. I have a AFE cold air intake with oiled filter and I found the IAC (intake air charge temp sensor) was pretty dirty looking on the air inlet side and was a nice blue color on the backside. Bought a new one for $26 and haven't had the misfire code or rough idle in about a month or so. Its a quick easy cheap thing to change to see if it helps your issue also

It's just the stock air filter. I checked the filter itself and it was clean, but didn't think of the sensor.

Did you have similar issues with rough idling and the check engine light flashing when you tried to drive mow than 20 MPH?

I swapped the plugs today and the issue persists. It doesn't sound terrible on startup, but once it gets running the idle is on the lower side and you can see and feel the truck shaking.

 

[Rebob0510]

My truck would seem to idle normal at startup but after it warmed up it would idle rough, you could definitely notice it in neutral but it wasn't as noticeable when in gear and stopped at a light. My check engine light was constant on the dash (P0302 CYL 2 Misfire). After I changed the sensor the idle definitely cleared up and after about 150 miles the check engine light went off and hasn't been back on since.

 

[shayram]

Probably a bad fuel injector. Just happened to mine. Out of the blue and no warning. Tried the stuff you did and nothing worked so I drove it to the dealer. Yep bad injector at 54k. they replaced the one injector and all is well.

 

[JayP_1500]

All - thanks again for your suggestions. I wanted to update the post with the latest info.

I unplugged the negative terminal overnight and reattached it this morning. I turned it on, but it still had the issue. Had my OBDII tool hooked up and the misfires climbed up as expected. I realized that I had hit the grill pretty hard with water when I washed it, and was wondering if I possibly put too much water into the air intake (right behind the grill) and maybe some excess moisture went through all the way into the cylinder. I made an appointment at the dealer for tomorrow and sat the truck in the sun all morning into the early afternoon.. I decided to get a bottle of Iso-HEET this afternoon as a last ditch effort.

I poured the bottle into the fuel tank, and started it up WITHOUT a check engine light. I decided to drive it and see how it responded. I took it about 30 miles total before hooking it back up to my OBDII tool to monitor cylinder 3 for misfires. To my surprise, I only had 3 total misfires, whereas before I was in the thousands within a few minutes. Now, I cannot see how the HEET could instantly clean this up, so I am wondering - is it possible my capless fuel tank flap did not have a proper seal, and adding the HEET caused the flap to go in and out to reseal?

It was an immediately fixed on startup and the HEET didn't even have a chance to mix with the rest of the fuel. So my theory is either the fuel tank flap is the culprit, or something finally dried out and I am no longer misfiring on cylinder 3. I'm really hoping when I start it up tomorrow morning I am still clear. Anyways - thanks again for the help. I will post an update if anything else happens.

 

[RiffWrath]

Thats good to hear JayP.
Give yourself a pat on the back. You deserve it.

 

[kapinallinen2]

is it possible my capless fuel tank flap did not have a proper seal

It would throw a code for a vacuum leak.