Truck has run fine for ten years. Just spent six weeks with the motor pulled to change the rusted out oil pan and replace a cracked Y-pipe (pan done in three hours, Y-pipe took the six weeks to get from Ford).

Anyways, once I got it running again everything seemed go south: Day one back on the road and had to replace the upper oil pressure sensor (fuel/oil sensor); Day two back on the road and the GPR went out.

Now when its cold it will start no problem, but for the first 10-15 seconds it runs like it is missing a couple of cylinders. The whole truck shakes to one side and the engine revs up and down, up and down. Make any sense?

After that first 10-15 seconds it smooths out and idles correctly. No problems while running.

Possible bad GP? Tried to plug in the block heater just to find the cord shorted out. Never plugged it in, ever. Never had too. Just confused as to why it runs so rough when starting.

Ran synth oil for years. This time flushed the motor and refilled with normal for cold weather.

 

Thats probably your problem. I have had mine for almost 2 years now. Last winter I used synthetic started fine even at 0 degrees might lope for a min but once it got a little heat it was fine. However up until 2 wees ago I still had 15w 40 in. It sat for almost 2 days I went to start it it barely cranked over and I have brand new batteries. Then it finally picked up and started. Change your oil. I put my used oil in my fuel tank to use cause its about 4 free gallons. I did it 2 weeks ago you wouldnt believe how slow that 15 40 poured into the tank after it was cold again. And mind you it was about 40 that day. Drain yours and let it cool. Then move it and see how thick it is. Then fill your synthetic in and be amazed at how fast it comes outta that bottle long post haha

 

HEUI doesn't like thick dino oil.

fully synth all the way.

---AutoMerged DoublePost---

Also, a good test is to poor some dino oil in a glass. do the same with some synthetic.

put them both under the truck over night. in the morning, pick up the dino oil and try and swirl it around the glass. then try the synth.

you'll never want dino oil in your engine again.

 

And another possibility, you have one or more glow plugs out. My 1990 7.3 acted like that when about 1/2 of the glow plugs went bad. Otherwise I agree, most likely oil too thick when cold for the injectors to operate properly at first light off.

 

when its cold it will shake because its your motor trying to suck cold thick oil u need to plug it in it will help a lot. and will hurt your motor because the oil pump will wear out from straining sucking cold oil. when its cold you have very little power because your cylinders are slowly moving so that's why you think you are missing cylinder.

 

So, replaced the shorted out cord for the block heater. Plugged in each night and no problem starting in the morning. Going to drain the oil the shop put in and go back to the synth I've used for the last ten years. Again, never had to plug my truck in since day one (thats ten plus years) until I had the new oil pan put on and the shop that did put in a fresh fill of normal weight oil for cold weather.

Thanks for all of the replies.

 

I run dyno and have never had issues with cold oil. Let the truck warm properly and go on with life. You have a GPR or Glow plug issue. Plugging it in just masked the condition. Your run issue has nothing to do with what type of oil you are running.

 

The GPR was bad when when I rolled it out of the shop. It went in when the weather was warm and came out when it was cold, so it could have been bad all summer. Replaced it so that is no longer part of the problem.

I've never owned a diesel longer than six years. So, is it normal for a GP to fail at eleven years? I can see the GPR failing after 8-10 years (along with most everything else), but what can go wrong with a GP? If I had done something stupid like use ether then I can understand a GP going bad.

Heres one: how can I tell if the motor is the original? Block ID? Not saying it, but not seeing how so many issues can show up all at once, unless the shop I took it to swapped motors on me.

Just to be clear: The truck went in to replace the rusted out oil pan and a front hub. Had no other issues with the motor, AT ALL. Temp was around 45-60f. When I got it back the temp was 27-38f; the high pressure oil sensor was leaking (fell apart in my hand when I took the harness off); the GPR was toast; and it starts like crap on cold mornings.

 

GPR's can go bad in days, as well as glow plugs. My truck has had the glow plugs replaced twice in 200k, once with a new motor and once because 3 were not working.

There is no way to tell if the motor is the original or not, not without a lot of research