Well I done it. I got a diesel. A 1996 F250 extra cab long bed 4x4. 7.3L 5 speed maual with 275K on the clock. It's my first diesel so be easy on me lol!

Anyway. When I drove the truck home it idled real rough. But after 1000 or so rpm it cleared up fine and runs smooth and strOng. But idling it's so rough it shakes the entire truck. This thing will be my dd in a few weeks so I need to sort it out Asap. Thanks In advance everyone!! Hope to learn a lot and I'm sure many many more questions will come lol
-Nathan

 

How rough are you talking? If it sounded for a moment like it was running on 6 cylinders, it could be the UVCH (Under Valve Cover Harness). If not, it could be the ICP sensor. I'd start by disconnecting the 4 plugs that run into the valve covers, and inspect them to see if they have burnt pins.

 

I will check in a few hours when I get Home. This is all new to me and my other truck is a 74 chevy. HUGE difference.

 

Unplugged all 4 connectors Looked fine aND truck idled WORSE with them unplugged. Unplugged ICP and made no difference. Also did a Google search trying to locate possibilities. The ebvp was unplugged, no difference. Unplugged the sensors at front left and middle of motor anD no difference. Also unplugged one next to the round thing in middle of motor under air cleaner? Not sure of its name? And no difference...
Side note. It will idle good for a minute or so then rough. Like its shaking BAD the rpm doesn't move just shakes. Take off is fine... also seems like there is oil e erywhere in this motor. Turbo on top motor and I have a leak somewhere... is that relAted?

 

The oil could be coming from the turbo pedestal. That's a pretty common leak. Is the oil pooled in the valley? Is it all oil, or is there fuel in it as well? I'm not sure if this could help, but try pulling the two bolts out of the fuel pressure regulator (Brass-colored) and on the side of the fuel bowl, and see if the screen in it has a bunch of junk causing it. Could be causing a fuel blockage, and as a result, a rough idle.


Next thing to check, if you have a large oil leak is the plugs in the back of each head. Reach your hand back, and see if you feel any oil there. There's a little bit of space between them, and the firewall.

 

Also the plugs in the head, maybe a O ring is bad and leaking.

 

don't idle the truck with a harness unplugged. just visually inspect when you unplug them and look at the pin you'll see that the plastic has melted around them if you have damage lookat the pig tails and harness under neat the valve cover

 

X2 with Pilgrimbizkit. They could have damage under the covered part of the harness. That said, since it idled poorly when you unplugged them, that would suggest they are working fine. Had it remained the same with one unplugged, you would have found your problem. LOL.

 

The valley of the motor itself isn't oily just like inside the air intake tube and stuff. I will check tonight again for the back of the heads. The harness connections looked good. I will look at the pedistal tonight too. Can't wait to get this figured out. I only left em unplugged for a second to see if it Differed. No CEL on dash either. I also changed tanks to see if that would help or make a difference. It did not lol. Also will note the oil pressure Guage read good (About middle) but temp Guage barely got up to the first Letter. Related? Idk.

 

Oil temp gauge is a idiot gauge, its only activated by 6 lbs of oil pressure.

 

My son just bought a 7.3 that has a rough idle as well. Also when driving it at cruising speed it seems to have a stumble or miss at low RPM. Any ideas. I guess we will check all these suggestions here and the ICP? as well.

 

Mine shakes horrible when at a stop light unless I keep the rpm up. I'm also going to check out the motor mounts.

 

You said your throttle response was normal? It doesn't act like you have air getting in to the fuel?


Also, is the oil in your HPOP reservoir filled up high enough? Should be about 1/2 inch from the top, I believe. I don't know if that could cause a shaky idle, but it'd be worth checking.

 

Idk what an HPOP is truthfully so idk. And after 1300 or so rpm it runs wonderful and smooth. Idk how to diagnose air in fuel? Boy before me changed the fuel filter but said it was like that before he did it.

 

The HPOP is the High-Pressure Oil Pump. It runs the injectors. If you look at the engine, you'll see the fuel bowl in the center (Under the plastic cover, if you still have it on there). The HPOP reservoir just a touch in front of it. Gray metal, with a couple of threaded plugs in the top.


If you have an air leak, you'll know. The RPM would "float" way up with any throttle, and slowly come back down. Some air inclusions can cause a shaky idle.