Hi guys, looking for some awesome help on here as I have gotten it before. I have a minor issue, truck is in the signature.

When the truck is cold, say first in the morning (even while plugged in) or even after being parked for 15 minutes or so (it is still around 40*F here) the truck will lugg a bit. By this I mean that it will drop RPMs a bit, around to 400 or so and then kick back up to recover, usually around 1000-1200. It will do this a few times, usually 5-6 and then be fine for the rest of the day. Seems like this only happens at times when the grid heater would kick in.

The truck was running fine till a couple days ago, I did change the air filter with a few Fleetguard filter from Genos. Is it possible that could be causing it? The truck was running a simple filter, looked like a Fram and I have noticed that the Fleetguard is a lot thicker. I am going to swing by Napa and pickup a test filter and try that for a couple days and see if that could be the issue, but I was looking for other suggestions in the mean time. There are no codes being thrown.

I also have a fresh fuel filter I was going to drop in, even though this one was changed with the last oil change. I have read some things about people trying some fuel conditioner as well, could that help?

Steps I have taken:

Oil level is in check.

I have tried taking the Smarty out of play, it is back on stock and still doing the same thing, so I am pretty confident that isn't the issue.

I filled the truck up again today with fresh fuel from another station than usual and I am still experiencing the issue.

Checked the air filter to make sure the box was all tight and there was nothing clogging the new filter.

I'm willing to try some things out over the weekend so suggestions are more than welcome.

Thanks again!

 

It's normal for the RPM to drop when the grid heater cycles, especially if the A/C compressor is also running. The A/C compressor is running anytime you're in defrost mode. Dropping to 400rpm is a bit extreme though, and may indicate a mechanically failing alternator (bearings). The surge to 1000rpm is just a timing issue with the ECM trying to add fuel to maintain idle speed coinciding with the grid heaters shutting off. The ECM is slightly slow to react to the sudden load caused by the extra draw on your alternator, so it adds fuel, but by the time it's added fuel, the heater has shut off, and now the engine is given fuel under no load, hence the higher RPM.

 

It never has bogged down this bad though when the grid heater would kick on. We were in the negatives all winter and it was never this bad. It was kind of just a sudden change as of the last few days. It boggs down to the point where it wants to die almost and then chuggs to catch back up.

There is an awesome shop here locally that will test the alternator for free. I will take it to them tomorrow and have them take a look.

 

I had the alternator and batteries tested and they tested out fine. I did change out the air filter and it was still doing it, so must have just been a coincidence.

I changed out the fuel filter and added some diesel cleaner to the tank. I just changed it about 5000 miles ago, but I think I could have gotten some bad fuel. It seemed to be a bit better, but I am going to let it sit for a couple hours and drive it again since it only seems to happen when it is cold.

I will update this evening.

 

Wonder if your inline fuel heater is working ok. This preheats the fuel before it gets to your VP44. If it is gelling it could pull the engine down quite a bit. My 2003 had a recall for exactly this issue with the heater. Is this problem the same in summer or when the engine is warmed up.

 

It seems all better now. I put around 100 miles on the truck today after changing the fuel filter and adding some diesel cleaner. I may have picked up some bad fuel along the way and it clogged up the fuel filter. It was a bit nasty looking, especially for only having around 5k miles on it.