Need some help.

[jdtheiss]

I am a first time diesel owner. I recently bought a 95 F250 4x4 auto with 175,000 miles. It was running fine when I bought it other than tough starts in cold weather when heater core not plugged in. I drove it to work one day and it was running good. Went to drive it home and noticed the engine was idling rough. I got on the highway and engine was not running smooth. After further testing, here are the symptoms. Rough idle. When driving, if rpm's are near 2000 I can still tell the engine is not running smooth. When I get the truck up to 45 mph and it shifts into overdrive, the rpms drop like they should to near 1500. The engine then gets rougher, shaking the cab. I also noticed especially on the highway between 50 and 65 mph, the speedometer started swaying back and forth. When trying to accelerate after dropping to lower rpm's, the engine gets rougher. The engine seemed to be running fine until i got in one day and it changed to the symptoms I just described. I changed the oil and fuel filter and have not noticed a change. Does anyone know what could be wrong?

[bondsman]

Cam Position Sensor (you should always have a spare anyways), check the under valve cover harness connectors for burnt or melted areas. Get it to a scanner to see if it will give you any codes. Exhaust back pressure sensor tube clogged? That should get you started...

[jdtheiss]

I used scan tool at auto parts store and it showed no codes. While checking for codes, the engine stopped. Started again and ran codes again, engine almost stalled then kicked back in. No codes.

I have been looking at cps info on internet. Seems there is a difference in opinion as to which is best (blue, grey, or black). Not sure which one to buy and were to find online. Ebay has them cheap(motorcraft), but not sure if they are any good.

[jdtheiss]

Where can I find the exhaust back pressure sensor tube?

[lhsnbsaoa]

It's on the front of your motor above the water pump. The sensor is round with a two wire connector coming straight out of the top. On the bottom there is a small tube about 1.5 feet long going to the bottom passenger side exhaust manifold.

[jdtheiss]

I replaced the air filter and cps. Hard to tell if rouge idle improved or if I am just more used to it now. There is still obvious shaking of engine and steering wheel when truck goes in overdrive between 45 and 55. Slower speeds with higher rpms is smoother and when I get up to 60 mph it is a little smoother. I can still feel a dull thud in the engine while it is running at the smoother speeds. The speedometer is still shaky between 45 and 55 mph. I have not tried everything mentioned yet, but am working on it when I have time. Any other advice would be helpful.

[dannanw]

get to a better scanner, such as AE or a snap-on type. also sounds like a trans issue to me, not an engine problem......just my $.02

[jdtheiss]

The fact that I noticed the engine running differently at the same time I began having this issue makes me think it is engine related. Anyone know where to find a better scanner in the Kansas City area.

[jeffh286]

i've been having the same problem some times i have to turn my od off just to stop the shaking someone told me it could be injectors since it idles rough too not just when driving so i dont think it would be the trans good luck

[spirittrakker]

I'm having the exact same issue with my '99. Put it in the shop, they say that the number 2 injector is probably going bad, but not so as to throw a code yet. They pulled the valve covers, replaced the glowplugs, and the wiring harness under both valve covers, and gaskets. Checked compression, and all were right at 400 psi. The thing is, at 369,000 miles, the injectors are all going to need attention at some point. Do you pay $500 to $700 to get one replaced, or bite the bullet and get them all done at once? Tough call, don't need to be without the truck for long, but it hauls the welder that turns the dollar, you know?