Ok, I've pretty well confirmed with DP that the tune is not defueling, which the absence of codes support. So, what else could it be?

Fuel pressure - Could the fuel bowl be slowly draining by fuel pressure that is too low to support the demand of a long uphill run? I'd think I'd have some other symptoms if that were the case, and I don't. Rich asked if I was seeing smoke when the "stuttering" is occurring, and I don't think so. Can't say for sure, though.

Low oil pressure - Might my stock injectors be demanding, and T500 supplying, more oil than the LPOP can support, so the reservoir is running dry on long hills?

IPR - I suppose the IPR could be faulty, but wouldn't I see a code if that were the case?

I don't expect you guys to solve this, but I could use some help with troubleshooting. Buying a fuel pump, LPOP and IPR seems like the wrong approach...

Mark

 

Mark, I don't think you will see a code for the IPR. What is your IPR duty cycle?

 

Mark, if you datalog ICP, Duty Cycle, Speed, FIPW, MAP, EBP, baro and engine oil temp we can graph it and get a better understanding.

When this happens does the fan clutch lock and the motor sound like a small hurricane?

 

I'll do that. I'm hoping to tow again in a couple of weeks. I wondered about the temp thing, as I was having high oil temps on long grades last year. I think the new radiator fixed that, as I never saw EOT over 228* on even the toughest climbs on my last tow. The issue at hand remained.

Mark

 

Another thread resurrection. I towed again last week, though on a road with shorter, slower climbs than I70. I fouled up Torque logging, but was watching things: Oil temp <220*, FIPW in the low 3ms range, boost <20psi.

On a several minute climb (Crow Hill out of Bailey, for you CO guys), I got slight stuttering as I approached the top, and could see the ICP "bouncing" at the time.

Whatever is going on, it's strongly related to how long I'm on it - it takes many seconds to a minute or more to occur - and not to short bursts like entrance ramps. I can get on it really hard all the way up to 65-70mph with no stuttering, at all, when entering the highway, and boost will be 23-26psi when doing so. That should eliminate "tune defueling" completely, correct?

Could it be...

Fuel pressure - I've not measured this, but could pressure fall to the point that the bowl is slowly draining? Would I see other symptoms of low fuel pressure? (e.g. hard starts, etc?)

Low oil pressure/volume - Could the LPOP not be what it once was, and the HPOP reservoir is draining on these long climbs? I'd think that would cause ICP to fall a good bit further than the 1800-1900psi that I'm seeing (from 2400-2900 that I see on climbs)

Flaky IPR - Doing something odd when high pressures are maintained for more than a few seconds?

What else? I'm not in a position to throw unlimited time or money at this thing, but I'm so happy with the way it's working otherwise that I'd like to get this issue resolved.

Mark

 

Have you dropped the tank? Other people have had problems like this in the hills only to spend lots of money at dealers changing everything and it was in the tank. If it isn't there at least you know its clean, and it's free if you do it your self.

 

Are you thinking of dirt in the tank? Would it show up in the filters? I am pulling both of them today, an will post results.

I did the in tanks mods years ago, so I'm assuming I wouldn't have to redo them. Fair assumption?

Mark

 

Yes, if you removed the in tank filters and put a filter on the out side that shouldn't be a problem. If you removed the filters and know outside filter maybe even the screen in the fuel pump could be a problem. Fuel pressure would tell you that under a load only.

 

I pulled both the pre-pump and stock fuel filters, and both looked perfectly clean, with no crud that I can see. I'm replacing them both, but probably won't drop the fuel tank.

Does this sound like a fuel starvation problem?

Mark

 

It gets back to fuel pressure. If no inside filters remain and out side is clean u just have to know the fuel pressure but it now sounds like map or something.

 

Did you notice whether the IPR duty cycle is climbing or falling when this happens?

 

I did. It falls.

Mark

 

Did you eve find out what was causing your engine stuttering issue?