Misfires after valve cover gasket change

I finally did the valve cover gasket today after 3 years of dealing with leaks. It took me about 4 hours, but I'm not the fastest wrench. I buttoned everything up and went to start it. It caught once and died, then fired right up, however the idle is very rough. I pulled out of my driveway and took it up the road - obviously way down on power. It almost immediately threw a CEL.

I checked the codes and got P0300, P0302, P0304, and P0306. 1st is random misfire, the last are misfires on cylinders 2, 4, and 6. It's almost like an entire cylinder bank is inoperable (driver side.) Everything seemed to go back together well and I don't believe I missed any harnesses, however one of the hoses near the TB is obviously coolant as I got a lot of it on the passenger side of the engine. I don't believe all of the coils got wet, but it's possible there was some interfering.

I pulled all the wires to the driver's side plugs and the idle didn't really change. It's as if none of the coils are sending spark across the wires.

Any ideas on this one?

 

Did you mess with your fuel rail or injectors, you shouldn't of but maybe it happened. Is there fuel leaking at the injectors?

 

Make sure the coilpacks are plugged in all the way

 

I did unplug the injectors on each side to allow for better clearance when removing the valve covers, but they all got plugged back in with a click. I didn't unbolt or fiddle with the rail itself or any fuel lines. I don't see any fuel leaking, nor do I smell any, though I did get a slight whiff while I had the intake manifold off. Nothing now though.

Pulling a connector to a coil pack (any of them) will cause the engine to die. The packs all seem bolted in securely and all of their connectors are clicked into place. Nothing seemed to go wonky with the R&R except for the plastic wire shield on the driver's side splintered into a million pieces as I was taking off the valve cover.

 

I have a hunch that it might be fuel related. I got out my old (made in USA, that's how old) inductive timing light and clamped it onto each wire running to the 2, 4, and 6 cylinders. I got light on all of them. I'm not sure what would cause a failure of all 3 injectors on that side, or maybe something is pinched? It seems like I would smell fuel if the cylinders were being flooded, or possibly have some kind of smell from the exhaust, no?

 

Did a little more digging with my ScanGauge and Torque on my phone. The truck never leaves open loop, even when it's up to temperature. I get no voltage on the O2 sensors bank 1 sensor 1 or bank 1 sensor 2. However, even if the ECU is ignoring the O2 signal like it does when it's cold, it should still idle correctly and produce some kind of voltage. I wonder if the O2 sensor connection is fouled in the same place that directs the driver's side fuel injectors to pulse?

Also, I noticed that the longer I let the truck idle and warm up, the worse the idle got. It never started to choke and die, but it felt rougher, likely a result of the RPMs going down...

 

I assume you retraced everything you unplugged and made sure everything is back on? I did valve cover gaskets on 2 3.4L engines last weekend without any issues.

 

Well of course with everything back together, a lot of the "tracing" that someone might do is difficult at best. From what I can see, the plug wires and coil packs are secure, the injectors are plugged in, and all hoses are connected back where they were, even the ground on the driver's side of the engine. I'm trying to avoid tearing the whole thing apart to find that I did nothing wrong and there is something else I can try. Otherwise I'm not left with many other options.

 

Maybe disconnect the battery for a minute and see if it is confused.

 

I'll try that tomorrow - before work if I'm lucky. Otherwise I'll have to give it a go when I get home in the afternoon.

 

It is pretty common on the V6 to get the wires from the coils on the passenger side to the plugs on the driver's side to be wrong after disconnecting.

 

My moneys on that. OP definitely make sure you put the wires back on the right cylinders. That will exactly cause what you're experiencing.

 

I actually didn't find the plug wires to be difficult to keep track of. I did one side at a time so the cable lengths made it obvious where each plug went back in. However, I did double check this yesterday afternoon against this diagram and it checked out:

http://econtent.autozone.com:24991/...c152/80/03/70/f1//medium/0900c152800370f1.gif

 

Time for new wires.

 

I don't think all of the wires spontaneously decided to stop working after the valve cover gasket replacement. Plugs and wires are only about 3 years old, replaced with OEM. I had no stumbles or anything with the engine before the work.

 

If you don't notice any difference with the 2,4,6 cylinders connected or disconnected, it is the wires, their connections, or electrical impulses getting to the 2,4,6 injectors.
5 and 2 fire simultaneously, as do 1 and 4, and 3 and 6.
Your engine is only firing right now on 1, 3 and 5.
If 5 is firing, that coil is good. You need to see if 2 is getting spark. Take another spark plug and lay it on the engine and hook up the wire from 5.
Start the engine and see if that plug fires. If it doesn't, something in those wires is bad.
Any plug will do for this test, even a lawn mower plug, and it is a better method than having your wife hold on to the wire while you start the engine.

 

Truth be told, I actually did something similar to that yesterday while troubleshooting, though I did it with the plug out of the cylinder. The spark arced across the threads while grounded to the valve cover. It sounded a bit reckless, but I did notice it worked.

Despite having zero compression in the cylinder, the engine still ran. I did not smell fuel during this test, though I thought I would have if the head was exposed. This makes me think there's something awry with the wiring on the driver's side.

 

You are likely correct.
Plugs are harder to arc with compression that at atmosphere, but if the spark was a healthy one, look at an issue with injector wiring/plugs.

 

Ok, sounds like I have my agenda. Teardown should go a lot faster now. Are there any tests I can try to see if the injectors are firing while I have access to them? Not sure what I can do with the manifold, throttle, and MAF off the truck.

 

3 years is a bit long IMO. I would at least replace the wires and see. Good luck.