Ok had several 7.3's before. bought this from original owner great shape all around. drove it only a little first. then first freeway run felt a little sluggish and noticed a lot of that blackish opaque (it was dark outside by now) smoke when past half throttle or lugging at all, dont recall ever hearing any turbo spook or noise. parked at home, next day and ever since it has basically no smoke at all to speak of and super sluggish, have to rev 2500-3200 to have any umph really, motor starts and idles great, obviously has the torque there as it drives fine otherwise and will move, it just drives like a non turbo rig. I'm thinking it might be a sensor that nots telling the turbo to spool, or could be bad turbo with really crappy timing the day i buy it or ?????? any suggestions? Thanks for the help and I look forward to hangin out on here with you guys now that I'm back in a psd

 

Exhaust back pressure valve "EBPV " probably stuck on. All you have to do is un plug it. It's function is to warm up the motor when cold. If it sticks on it will not have much power. Also it will sound more like a jet then a 7.3 while the valve is on

 

Thank you. I will google where and how to unhook that to give it a try. Ill check back in and let you know.

An update... I unhooked the MAP sensor just to see and it changed nothing at all except giving me a CEL. checked the vacuum tube to the MAP and it was clear.

 

I thought though that if the EBPV was stuck open you would have a lot of black smoke and no power. That is the condition I had when I first took off, but the next day and ever since then I have zero smoke (no I am not wanting black smoke, I know that is not power!)

could the EBPV have caused the initial heavy smoke and no power condition and then that have caused a different issue like sensor or HPOP malfunction that is now causing this no smoke no power condition???

 

another update. unplugged the EBPV actuator sensor and drove it. no change at all!, same driving, same power, same no smoke, same no audible sound of turbo

 

I'm starting to wonder if its an electrical issue or if its a fuel delivery issue. Heres my thoughts please someone tell me if I could be right on any of this..

so had lots of smoke but low power, sounds like no boost, could be ebpv issue or bad turbo.
then next day and ever since, no smoke at all even with disconnecting MAP sensor, and with disconnecting EBPV, no power, feels like same umph whether its quarter throttle or full. been this way since I bought it so I have no frame of reference unfortunately.

 

These trucks don't smoke much at all in stock form. Also, they aren't very speedy either. Did you drive it with the map unplugged? Do you notice any soot on the firewall? I don't suppose you have a boost gauge? Any cel at all? Have you checked fuel pressure?

 

I did drive it with the MAP unplugged and no change what so ever!!!
same response with the EBPV actuator sensor dc'd
and same driving it with the EBPS sensor dc'd
dont think I saw any soot on firewall, no boost gauge yet, but a digital multi-gauge is in the mail as we speak that will also let me see codes. no ECL except when I dc'd the MAP.
I have not checked the fuel pressure, that is climbing higher on my list although I dont know how to do that myself just yet. any info on that would be appreciated as well.

I just bought this from original owner (crazy I know) excellent shape. owner said he never took it over 2200 rpm and basically babied it. I talked to the shop and mechanic that did all maintenance on it since it was new and he said this guy babies all his rigs and is meticulous about maintenence and he would buy a rig from him any day! thats good butttttt. he said he babies it too much and we all know they do need a little cleaning out with the throttle from time to time. he suggested checking the tube and sensor visually (EBPS) I just peaked and it is is about 50% plugged in the bracket angle connector and the tube looks partially stuffed with soot and build up. Mechanic said that basically when that happens the EBPS will get stuck at what ever pressure it is at and it will just stay there, sending the exact same EBP info to the PCM. This could easily explain why there is absolutely no change when dc'ing any of those sensors. this week I plan to either replace all said parts or do a major PB cleaner soaking and digging to clean them. I will update and let you know if that fixes or helps. I know the 5 speeds are not as quick as the auto's but this definitely is being robbed of power and boost.

 

Fuel pressure is checked on the drivers side of the fuel bowl/regulator. There is a schrader valve there. You can just use a cheap stick tire gauge, put a rag around the valve to avoid much diesel spray.

Been a lot of debate on that ebp sensor and what it really does to the truck. Do some searching on this site and you will probably see what I mean.

 

A clogged CAT describes your description of the symptoms, especially if the truck was used for short runs and babied a lot. It's not really a CAT like gas rigs but more of a particulate filter with lots of very fine mesh screens interwoven.

 

Up pipe leaks, check for carbon (black) along the fire wall behind the turbo, up pipe to collector o-rings might be leaking. Get a flashlight and from under engine look up at exhaust manifolds especially at rear (#8 and #7 cylinders) to see if there are exhaust leaks. Check bolt heads (visually) on exhaust manifolds same as above, not uncommon for the heads of the bolts to have popped off causing manifold leak.

jrc