Rough Cold, Smooth Hot
 

My truck runs very rough and lacks power when cold, even during the Texas summer. Once it warms-up, everything is fine. It's almost like turning on a light switch. If it's plugged in for a couple/few hours, it's smooth as soon as it starts. I'm assuming it likes the oil once it reaches a specific temperature. Any ideas on what my problem is?

Yep, you're actually on the right track. Oil.

What are you using now?

How often do you change it?

Are you using any additives in the oil?

I'm running T6 and changing it every 6k. Prior to my most recent oil change, I had used Hotshot's Secret 3 or 4 times. I'm not using it now, and nothing seems to be any different. Fresh oil or tired oil, additive or no additive, nothing seems to make a difference except oil temp.

Are the miles in your signature the same as on the injectors and IPR??

Yes, except for one or two injectors. I was hoping injector replacement was left out of this conversation.

Try using Archoil 9100 in your oil. It made a huge difference in my cold start and idle! I convinced a buddy to try it in his 6.0 an he's sold on it now too.

AR9100-16 Archoil 16oz Friction Modifier https://www.amazon.com/dp/B005UO6EWE..._ehVzwbR2SDQX0

Dude I started the same exact post a few days ago on the same exact subject! 175,000 miles. Original owner. Well taken care of. I did Hot SHot 5,000 to 6,000 ago. To no avail! I am attempting Archoil today. I have the FS 2500 Oil Bypass System so I had to check with Archoil and FS 2500 to see if the Archoil will penetrate and work with the filtration system. Both Companies said yes! I will keep in touch

The symptoms are straight out of the textbook for injector lower poppet valve seat wear.

I'm sure a new set of injectors would solve my problem. I guess I'm just in denial.

It's relatively easy to confirm it or rule it out with a set of feeler gauges. When the armature plate to poppet body clearance is less than 0.0015", that's when they usually start showing the signs of wear, in the form of running rough when cold.

I'm dealing with the same issue. On cold start under 43 degrees my Excursion runs really rough, but after it heats up, smooth as can be. It has 143,000 miles, and no codes for glow plugs, so I am thinking injectors are worn out.

I guess I should feel lucky that I got 343k out of them.

You won't necessarily get any glow plug codes. I would check the GP system and make sure it is working properly. I know you have the GP control module and I am not sure how to check it, but I am sure there is a procedure and a search will turn it up. You certainly can ohm out the connector and make sure the GP's themselves are in working order. 143,000 miles is a little soon, but mine started getting bad the winter I was around 150,000 miles, so it CAN happen. I just would hate to hear that you threw $1000+ at a problem that could be a bad module, or several bad GP's and then had to replace them on top of buying and installing new injectors.

I'm really thinking my issue is something other than injectors or oil temp. It's a "light switch" type of issue. When my motor gets warm, the "light switch" is turned on and everything is great. If I plug in my truck, everything is great. If I don't plug in my truck, it's really rough, similar to when my IDM went out and I was running on half the motor. When I leave in the morning with a stone-cold engine (whether it's 30* outside or 90* outside), the "light switch" comes on roughly at the same intersection about 3 miles from home. So, I'm leaning towards an electrical issue. Any ideas?

You can check the UVCH and make sure it's not loose, ohm out the injectors and glow plugs, but it really sounds like injectors. I just replaced mint last year at 340k, and it was doing pretty much what your describing.

The reason it feels like a "light switch" could be because the injectors either work or don't, until the oil warms up enough to flow through the poppet valves.

Check the poppet valve clearance like was mentioned earlier, ohm the injectors, and do a compression test before replacing the injectors. Also if you have some kind of OBD2 tool to read live data see what your HPOP and IPR is doing just to rule those out. At 340k, things start to wear out. i'm hoping to get a t500 this year for mine.