Sorry, it is not the relay or glow plugs. Injection on these engines is affected by the condition of the engine oil. Too low oil level will cause problems.So check it. If good, than you will need a computer diagnostic done on the engine (dealer or shop), to figure out the problem. It could be anything from an injector to a sensor.
Visit http://www.nexiq.com/ for code reader info. These are cheap to buy at http://www.ebay.com/.
Several things can cause the problem you are describing, I will list some of the more common and try my best to explain each.
On a 96 444E there is what is called a turbo back pressure device. What this is is a flapper in the exhaust outlet of the turbo charger. Its function is to help the engine reach normal operating temp faster by blocking the exhaust. This will open up once the oil temp reaches 140 degrees. When closed it will reduce engine power except for full throttle. Yours may be malfunctioning and staying closed when it should be open.
Next would be oil quality. The injectors in your engine are hydraulic actuated, the hydraulic force comes from the engine oil via the high pressure oil pump. If your oil is in need of a change or the wrong API spec your injectors will not fire properly. You need to run a good quality 15w-40 diesel engine oil meeting spec cf-4 or higher, I believe they are up to cj-4 currently. If your engine is high miles and seems hard starting you may also have injector orings leaking, this would require a shop to test for and repair.
After all is said and done there are some sensors and one regulator that directly affect performance. First would be the IPR sensor, (injection pressure), it is located on one of your cylinder heads near the front it senses the oil pressure supplied to the injectors. The pressure is regulated by the IPR valve located on the left side of the high pressure oil pump in the front of the lifter valley, really hard to see but check the wires going to it. Next is the exhaust back pressure sensor sensor it tells the computer what the exhaust back pressure device is doing. And a boost sensor that tells the computer how much boost the turbo is making.
If you are getting a check engine light it may be best to get some flash codes out of it before digging much deeper. To get the codes hold down the diagnostic button on the dash and turn the key on, release the button and count the flash codes on the engine light, they are three digit codes. Post back with them.
This sensor goes out a lot over time. Change the camshaft position sensor, and your problem is solved.
I changed the camshaft position sensor and It is still having the same problems as before. i followed all of the wires and there are no frayed or loose connections that I can see
Here is what its doing one more time.
I turn the truck on and it idles fine at 500
1 minute later I give it gas and it wont go above 900 without cutting out
5 minutes later I can get it to about 1500
30 minutes later it wont go over 2000 without cutting out
an hour later it stays at about 2000 to 2100 then cuts out
temperatures at 180
no check engine lights
and no abnormal error codes
any other sensors you can think of?
Yes , there is one that will cause problems, but sometimes does not issue a fault code.
It is called the IPR (injection preasure regulator) located on the side of the high preasure injection pump (driver side). Just follow the wires. It is screwed into the pump. You will need a deep socket to get to it. It is an electro spool valve that will stick with time.