On an earlier post I was considering swapping my pump out to a friend and then ordering a new/rebuilt for me.  Now that I have his truck here at my shop I am glad I didn't jump and do that.  Upon driving his truck its misses and surges at initial throttle and at light driving conditions.  When you put your foot in it, it takes off and runs great and doesn't miss or surge.  It even does it going down hill holding it in third gear with very light throttle.  The best example I an give you is it feels like a gas engine with a bad spark plug or spark plug wire.  Differenece is Once you get past half throttle it runs great.  As long as it has a strong pull it runs fine.  I'm going to check lift pump pressure and for air but I really don't think that is the problem.  I would think if the problem was with either the lift pump or IP it wouldn't run so well under heavy pull and throttle.  I'm leaning toward a APPS or Manifold pressure or Map sensor.  It is a 5 speed manual.  Haven't checked for codes yet, the light is not on but did come on for him a couple of time but goes off after within a minute or two or after cycling the key off and on.   Ideas??

Edited January 20, 201510 yr by WesHawkins

I'd say you're on the right track. There's a good write up o how to test the APPS in the article databse. How many miles are on your buddys rig? Any poweradders, low power, or excessive smoke?

Most likely not the APPS sensor or MAP sensor. You can unhook both and it should idle normally without them. Would be a good idea to get the codes though it gives more clues. I'm going to have to say it most likely injectors acting up. As they tend to age and wear they get pissy and pop at a much lower pop pressure. So I would consider having the injectors pulled and pop tested. A matter of fact my RV275's injectors failed the same way random misfire at idle fully warmed and under load it goes away. But on a pop test stand the pop pressure was as low as 240 bar way below 310 bar it suppose to be. Then as they start to pop they just piss a stream of fuel no atomization at all then POP! they would atomize the last bit. But diesel engines can burn liquid fuel it has to be in a atomize form so the cylinder heat can covert the liquid mist to a vapor then it burns.

This truck starts fiine an runs fine at idle and it runs fine when accelerated heavily.  It misses and surges just off idle up to half throttle with little or no load on it.  I tested the APPS sensor and found using a analog volt/olm meter at about half throttle the needle on the meter stops moving with the throttle movement then starts moving again.  Going to check a few more sensors tomorrow and will probably take mine off my truck and put it on this one and test drive it.  I'll post what I find.

So there is a slight flat spot not a failure. Might be something you consider replacing soon but its not you cause of misfire. Might be easier to grab a live data tool and just watch the data while driving. Then you see everything the ECM sees. 

I also started digging around it and found wiring harnesses that aren't factory that tap into the APPS and go under the dash somewhere.  Looks like he might have some sort of power adder on this after all.  The only scanner tool I have that will do runnning live data is an Auto Enginuity program that uses my laptop.  My old laptop crashed a few weeks go and I still have to reload the program onto my new one.  I haven't used it that much and don't know what the information its sending me should be so I'm not sure what to look for.  This will be a learning experience.  Glad its on someone elses truck.

Sounds like a Bank's Box. You might try removing all that stuff and returning to stock and see what you get.

Is it possible the APPS is actually giving intermittant signals fast enough that it feels like a miss?

Well well well guess what I found.  I had a little more time to spend on it today after finishing another job and what do I find, a Banks Ottomind power control box stuffed under the dash. Can I see a show of hands from those that think this is probably the problem. Now I will probably have to disconnect this unit and go back to factory to rule it out.

More than likely. I saw one that about 30 seconds after starting it would give a dead pedal and would not shut off. The Edge box was the cause. Now you know where those wires went to!

Sounds like a Bank's Box. You might try removing all that stuff and returning to stock and see what you get.

I think you hit the nail on the head.  Going to put it all back to stock and drive it.  The thing is I have a 2000 Dodge and I after driving this truck with this power box I see very little difference in performance over my stock truck.   The only thing I have done to my truck is a FASS lift pump, a Fleece cooling system bypass and a 4inch exhaust.  Its runs great.

So now start from bottom up and redesign your mod's the way you want them.

WesHawkins  and   TFaoro...      are  these  two    battling  the  same   problems?

Bingo!!!  Took the Banks Ottomind off and hooked it all back up to factory harnesses and it run great.  No more surges or missing.

Beat it with a hammer....

Ed

Beat it with a hammer....

Ed

The owner of the truck is going to do that.