cougar

I'm more use to a 1st gen so this seems weird to me.
01.5 auto 175K miles
#1: My fuel mileage is slowly increasing. When I first got the truck it was around 16, now it's around 19. I haven't made any changes sense it started doing this. Driving habits and route haven't changed.
#2 My fuel pressure increases a couple psi when the temperature starts dropping below 20°. May be from the motor oil in my fuel additive mix.
#3 Low rpm throttle is twitchy only when it's cold (below freezing) outside. Runs fine after the engine warms up a little. Fine at idle, fine over about 1200 rpm.
Any ideas?

KATOOM

Maybe I'm not sure what you're asking.

cougar

Okay, I drove this thing hard around town all week doing parts runs for work. Close to 100 miles worth. Got 17.6mpg on the tank, 420 miles total. The only thing I can think of is the transmission is starting to break in. I do hate it when it shifts on the ice unexpectedly.

DIESELWRKS

still confused. is the tranny a new replacement?
175k i would think its already broke in.
is the 01 a newer truck to you. my fuel pressure reading is slightly higher when its cold, also the fass pump is a little louder when its cold too. I
get 19mpg on freeway with a baby foot.

cougar

Have about 2K on the overhauled tranny now. Picked up the 01 last spring but haven't driven it much until the transmission was done. It had a few issues. When I first got it, fuel mileage was terrible. The transmission was on its last legs, but still functional. After the rebuild, my fuel mileage was still lousy. Then it started going up. The cold throttle thing is like it is surging, fueling then defueling randomly. I have another APPS just in case. I have the FASS adjustable 95 with a draw straw. The in-tank pump was one of the above mentioned issues along with a worn out turbo.

Dieselbuilder

Can not guess check for codes

KATOOM

I wasnt really understanding what you were asking until now.....

1) The fuel mileage increasing can be a result or many things affecting. Yes the oil in the fuel could be a contributing factor as you're now adding lubrication to the VP which may be just enough to aid in fuel timing and/or the oil is adding a slight amount of BTU to the fuel energy.
Also, the 2ng gen 24 valve engines are fully electronically controlled and are very sensitive to improper voltage/amperage levels. Therefore two batteries which are not in good and/or similar condition and corrosion issues in battery cables or any other major electrical connection and ground can all cause strange and unexplained issues. Sometimes even phantom issues.

2) Fuel pressure fluctuations from ambient temperature is normal. Not all gauge types read the same fluctuation as its been found that some people experience a drop in pressure by a couple psi in the winter whereby some people experience an increase in psi by a couple psi. And all visa versa in the summer. Generally whether the gauges are electronic or mechanical may determine which was the psi will go too.

3) The ISB engines have very twitchy throttles. That takes a bit of getting used to. But if the twitchyness changes with the weather then I'd lean towards something electrical being the cause. Maybe the APPS, maybe not. Maybe just the changes in fueling while the engine is cold. You could reset your APPS and clean the MAP and IAT and see if that helps.

Remember, battery condition and corrosion are big contributors. So make sure the batteries are both in good working order. Maybe have them load tested separate from each other and the truck. Also if you live where there's corrosion from road salt/calcium chloride then make sure corrosion isnt the cause.

cougar

I have put about 4K miles on the truck sense I bought it. I have been using my additive from day 1 which is 50% 2 cycle oil, 30% power service, and 20% new motor oil. The PO said they ran power service regularly in it.

The batteries were one of the first thing I replaced when I got it, one was DOA. 1st gens are subject to similar electrical issues, so I'm up on the common ones.

The apps was reset and there are/has been no codes sense I've had it. The computer has been "flashed" twice before I got it. Figured the throttle thing may be normal, just paranoid about all this electronics stuff. IP failure, APPS failure, transmission freaking out are some of the common problems I read.

I have a lot of miles with 1st gens, so this thing feels very abnormal to me. Seems me and the computer don't think the same way. Doesn't fuel like I think it should and doesn't shift when I think it should. Drive by wire, totally different to the 1st gen.

I have a lot to get use to with this truck, so bear with me if I ask with what may seem to you as stupid questions. As I'm learning to live in a new world.

DIESELWRKS

you put regular engine oil in your fuel system of your VP truck.
interesting.

cougar

Instead of waste motor oil. I have lots of it left over from empty (not quite) barrels. The price is right, free. I use a small amount as a filler though iirc cummins says you can use 5% WMO.

cougar

Well, things are getting worse.
Started getting random slow starts and now this morning at 5° no start, just cranks. Cranking speed is normal, fuel pressure 15psi, grid heaters are working as far as I can tell. May not be transferring the heat though. Normally I plug it in for a few hours before starting in the morning except on the weekend. I wasn't expecting to be called into work. I've had a slow start even at 30°. It's random, most of the time it light right off. A few times it had to crank for a while, like 5 seconds or more before it would light. This morning just crank, crank, crank,,,,,,,,,,, no fire.
What should I be checking?
Still no CEL or codes.

KATOOM

If it starts normal when the block heater is plugged in then I'd check the grid heaters for function. Make sure the intake is getting warm when they cycle initially. Especially if you're having trouble with starting in the 30* range.
That said, with the engine warmer, it will start easier.
So, I know you "think" cranking speed is normal but if there's ANY noticeable corrosion anywhere then you should consider more corrosion in places preventing proper voltage/amps and slowing the starter a bit.

cougar

I was planning on pulling the grid heaters and give them a bottle brush cleaning. I've has them on the 1st gen act like they were working, but wouldn't transfer any heat being coked up.
The thing is that it's random. Being warmed up hasn't been a guarantee that it will start right up. Over Christmas I'll net to get it in the shop and start pulling connectors. I was hoping there would be some tattle tail that would help me narrow it down. This thing has a lot of wires.

Dieselbuilder

Just a thought the next time you run the truck when you park it park it nose down and see how it starts in the morning then I will go from there with ideas !

cougar

Hard to do around here being so flat, but I'll see what I can do. Thinking the banjo fitting on the return line in the back?
Well, went out later and tried it again without it being plugged in and on the second crank it lit. Around 9° by then. Most often running on the 1st crank, but 2 is great for the temperature.