I pulled our trailer up to our favorite camping spot on Thursday (about 70 miles) and the truck performed flawlessly, even got 10 MPG with the trailer in tow (~7,000 lbs). Drove around on dirt roads for about 20-30 miles on Saturday at between 3,000 and 7,000 feet elevation and had zero problems. Hitched up yesterday (Sunday) and pulled the trailer home, once again zero issues and even got almost 12 MPG!


However, I pulled into our driveway loop and stopped and my wife immediately said "what's that sound?" at the same time I though something didn't sound right. The engine was missing, surging, and loping very badly. Put it in neutral and it sounded slightly better, but was still missing badly and surging a bit. 30 minutes before home I left the truck running for a few minutes for a restroom break on the way home and it was running smoothly at that time.


I let it cool down a bit and went to start it and it took 3 tries to get it running again. Was missing badly and surging. My first though was a vacuum leak since I have a bad EVAP canister. I pinched off the lines to the canister and it didn't make a difference. I finally left it running and went around pushing in all the COP and injector connectors, when I got to one of them it pushed in slightly and the engine smoothed right out.


What confuses me is that I've had this engine running on 8 cylinders before and it ran fine, not great, but not this bad and still started easily. Why would 1 dead cylinder make it hard to start and run so roughly? My lock tabs on my injectors connectors are broken though and they are being held on with zip ties that finally dried out and broke. So I guess I need to safety wire them back on. I'm relieved it wasn't something serious, but I am still baffled why a single cylinder made that huge of a difference on a V10.

 

Make sure that spark plug is nice and tight, early symptoms of a loose plug.

 

Plugs were done about 10k-15k miles ago (about 3 years ago, don't put many miles on my truck) with proper torque procedure, so hopefully that isn't the cause.

 

It depends on what you mean by "running on 8 cylinders" - because of injectors on those cylinders not firing? Or a coil/plug/boot issue?

Which of the two caused this most recent issue? An injector or a COP connector?

 

When it was running on 8 cylinder a couple years ago it was that the injectors that weren't plugged in all the way. Which was fortunate as I would have been dumping raw gas into the exhaust and destroying my cat. I believe it was one of the injectors again this time, so that part was the same, it was just a different cylinder than last time.

 

You can get replacement connectors on ebay - 8 for $9.
Search for - 8Pcs EV6 EV14 USCAR Fuel Injector Connector Pigtail

 

I thought about doing that when they broke during the spark plug change a few years ago. But honestly since the actual connectors are still good and it's just the lock tabs I think it would be easier just to safety wire them. I got pretty good at it back in my Navy days (avionics) and I think I even have some safety wire pliers somewhere in my tools. Thanks for the info though!

 

I suggest replacing them. I replaced all mine, cut and soldered each. They fit a lot better than the ones that were 15 years old.


I got them on ebay

 

Yeah, sounds like a bad plug. Mine did the same thing right before it spat it out of the head...