O.K. so I have had my 2000 PSD for about six months now, and this is my first diesel truck. I live in North Carolina, so it doesn't get that cold here very often, but now it is about 20 degrees F, and I definitely notice a difference in my truck starting. I work at an auto parts store, so I will be installing two new batteries tomorrow, even if I don't need them. Anyways, when I start my truck in any weather under 40 degrees, my truck likes to go from about 250 RPM to 700-1000 RPM by itself. I tried watching and listening a little bit today, and I think I heard a surging within the idle jumping up. As soon as I hit the brake or the accelerater pedal, it stops immediately and goes back down to 250 like nothing happened. I am mechanically inclined, but I am new to the diesel world. I was reading other forums, and how most people switch to 5w40, but I don't know if its cold enough here to do that. Please, any insight?

 

Couple of things, 1) are you sure you mean 250 rpms? I think they crank faster then that, Im really hoping you mean 650-750.
2) When its that cold out, and the motors cold, the rpms should go up to around 1000ish rpms, its trying to warm itself up. Thats also why as soon as you hit the throttle, or brakes, it resumes normal idle. (assuming you means 650ish idle, i dont see the truck maintaining 250 rpms) Now if its violently revving from 250 to 1000, (and I mean VIOLENTLY and fast, rocking the truck hard) you have a case of the romps, and thats what people have cured with the 5w40 oil in some cases. That also should stop once you hit the go peddle, ive never tried the brake pedal on that. But it sounds to me like it idles at around 650-750, then ramps up to around 1000, for warm up. Let us know if thats what it sounds like its doing, and well go from there!

 

Oh yea, and welcome aboard, I just saw its your first post! Youll find this is a very good source for knowledge.

 

yep, when it is cold outside the engine idle will increase and close the EBPV and make the engine sound like a giant leaf blower . It's all normal as the engine is trying to warm up. As soon as you hit the brake pedal it will idle back to normal again. Whenever it is below 30 I plug in the block heater and let her idle for 5-10 minutes in the morning before heading out. 5W-40 will help startups during the cold temps along with a diesel fuel additive that increases cetane.



Schaeffer's 9000 5W-40 - cure the romps and cold starts for good....

 

No, it is definitely revving below the first line on the RPM gauge.

 

does she sound like she is stalling..250 RPM is very low..it would sound like it was strugling to stay running...

 

When I had a battery going bad it would drag the motor down, drop the idle and make her sputter a bit and sound like she would stall. Nothing as low as 250rpm's though - that is low - I didn't know the 7.3 could idle that low. Do you have anything at your store that will read trouble codes from the PCM or is there anyone on this forum that lives in the area that has the Auto Enginuity Software and can check your truck out? Possibly a diesel performance shop close to you?

Checking/changing the batts is a good idea - especially if you are not sure how old or strong they are.

 

One of our trucks is doing something similar, and it doesnt get used much, so I havent had time to look at it. When it ramps up to 1000 rpms, does it stay there? If it does, you should let it run there for a little while, till it warms up a little bit, then it should idle. I knoticed if you let ours warm up a little it doesnt do that anymore, and I know thats not a solution, its a bandaid, but I havent gotten time to fix ours yet either!

EDIT: Now that I think about it, I think one or more of the glow plugs are going bad. Reason being, its seems like a couple cylinders arent firing, untill you run it a little, but thats on our truck, and I cant garuntee thats your problem.

2nd EDIT: (Sorry) If once your truck warms up, it idles normal, then I would bet you need to replace glow plugs on yours. Glow plugs heat up the cylinders when its cold out so it will start, and run/idle untill the cylinders make enough heat to run without them. If a couple are not working, and the others are, it will more then likely start, barely idle, and once warmed up, you wouldnt notice anything wrong. If all off them failed, it just more then likely wouldnt start when it starts to get really cold. But if they all seem to have failed, its more then likely the GPR. If yours starts, and acts like its running on only a few cylinders at that low an idle, its more then likely a couple of glow plugs.

Hope that helps