I used the search feature, but I'm still at a hold... want to see if any of you can narrow this down.

SHORT VERSION: low boost

LONG VERSION:
1. Driving back to North Carolina from Quantico... on an exit ramp and suddenly my check engine light comes on and the truck sort of shudders... was coasting when it happened.
2. The rest of the drive, the truck performs juuust fine except for when I try to pass and I'm missing, oh, about a third of my power. Boost builds fine up to around 12 lbs and then it stop dead and won't build.
3. I checked under the hood, and nothing looked crazy. I cleaned all the carbon off around the intercooler boots.
4. This morning, I tried to replicate on the way to work, and I can get to about 15 lbs and then it stops building boost
5. I don't see any evidence of blow by, no fresh soot around the intercooler boots
6. On the way home, I could get to 20lbs boost, then it would quickly drop to 14-15 and stay there
7. The EGT does NOT go over 700* no matter what, which is unusually low... I usually get into the 1200s when I'm hammering on it for more than 20 seconds
8. Driving down the highway I have 1.5-2.0 lbs boost at 55 mph. I thought I would usually see 4-5, but maybe I'm wrong

Recap of symptoms: Truck runs fine other than boost will not build. Normally I see 30-32lbs once the throttle passes half way. Have not seen over 20, and will not sustain over 15. There are no funny noises, whistles, whines, ticks, or anything.

I have an ATS housing, 6637 filter, DP Tuner (with 80eco, 140 crackhead, high idle, and stock.. tune does not affect boost levels too much with the problem), regulated return fuel system, magnaflow exhaust, and a dual-relief valve on the MAP sensor line (boost gauge is tapped into AIH port)

In my view, possible culprits in descending order of likelihood...
1. Intercooler boots
2. Up-pipe gaskets (no ticking noise though)
3. Turbo on the way out (no noises from it though)
4. Fuel starvation, possibly clogged filter (runs fine at WOT before boost reaches 15 lbs though)
5. ECM problems (not likely since other than boost, everything runs fine)

Thoughts??? I will consider trying the PVC end-cap trick soon. Not happy about having to chase goblins right before I deploy again since I'd rather spend time with the family, but when is it a good time for your truck to blow up?

 

If it were me, I'd check and tighten as necessary the clamps on the 6 boots, then eyeball the up pipes.

Did the CEL only come on the one time? Having the code would be helpful. Any smoke out the tailpipe when you're low on power?

 

If I hammer on the throttle for more than 25 or so seconds, the CEL comes on. Difference is, the FIRST time it came on, it stayed on for about an hour. Now, when I can prod it to come on, it only stays on for 90-120 seconds.

The only smoke I see is when I take off hard, which is normal. The only thing that really gets me is the lack of EGTs... normally this means plenty of boost but not enough fuel, right? I'm not getting boost. This raises the question, is the lack of boost the true problem, or is it symptomatic of a fuel problem which in turn limits the output (read: exhaust) enough that the turbo won't produce boost

I forgot to add, I changed the fuel filter about two months ago

Edit: I'll swing by our auto hobby shop when it opens later in the week and have them pull the codes for me

 

Hmm. My knee jerk reaction would be froze fuel, but being that you're in NC..there goes that hypothesis.


FYI most box auto stores cannot pull codes on our PSDs with their scanners. Believe me, I've tried. You'll need a mechanic with a quality scanner or someone with Auto Enginuity.

 

Unplug your ICP sensor, and see if anything changes.

 

Smokin - I'm on a military base, the auto hobby shop is a MCCS-run facility where Marines can go work on their vehicles, rent lifts, tools, etc and they have mechanics on staff. They've got pretty good tools, including scanners. Hopefully they'll have what I need. If not I'll run to one of the diesel shops around here

Clux - forgive my ignorance, what, and where, is the ICP sensor?

 

The short CEL will probably be your typical P1211 from the DP. The one that lasted an hour is the odd one. Boost leaks or fuel restriction typically won't trip a CEL.

A fuel restriction will usually give you a rougher running engine and general low on power under load or at high speed. Yours seems to be fine under acceleration right up to a certain point that seems to change. The only other thing that comes to mind to check would be your set up on the MAP sensor to make sure the PCM isn't seeing too high a boost reading and defueling you.

 

Front, inside corner of the driver's side head, it's a round or hexagonal sensor. Just unplug the wiring harness at the sensor and take it for a test drive.

 

Oh I gotcha. Hopefully they have a good scanner...

I've been on your base before, but just as a visitor

Driver's side head...can't miss it. Here's a pic of a really dirty one borrowed from Chris.

 

Sweet. I will try some of this out tomorrow and let y'all know what comes of it. Curiously, what does the ICP sensor do (and what does ICP stand for)?

 

It tell the "brain" what the pressure is in the high pressure oil system. ICP stands Injector or Injection Control Pressure.
When you unplug the sensor, the "brain" uses default pressure values rather than what the sensor is reading.

 

From Ford:


The Injection Control Pressure (ICP) sensor is a variable capacitance sensor that when supplied with a 5 volt reference signal from the PCM produces a linear analog voltage signal that indicates pressure.


The ICP sensor's primary function is to provide a feedback signal to indicate injection control pressure to enable the PCM to command the correct injector timing and pulse width and the correct injection control pressure for proper fuel delivery at all speed and load conditions.

 

Well, hellacious day at work so I did not get to mess with anything. Same problems on the way home, but watched more closely... boost built easily to 18 lbs, then over the course of 2-3 seconds, dropped down to 13-14 where it hung steady. EGTs still remain at or under 700* instead of the usual 1250* or so. Ambient temp 65*

 

small amount of oil under the ICP. As soon as I unplug the ICP, the idle shoots up around 200 RPMs, not sure what to make of that. Another day of working through lunch until well after dark... I'm shutting my shop down at noon tomorrow, I'll swing by my auto hobby shop and see if they have a scanner that will run on a PSD. Wish me luck

Still curious... why would the EGTs be so low, so consistently? Is it the BOOST that makes them go up so high? Or boost and fuel together (my thinking being that if I only build 14lbs boost, the MAP will only read enough air to put a certain amount of fuel into the motor... chicken and egg I guess)

 

Sounds more like a Under Valve Cover Harness (UVCH) to me. Above ~37mph, does the truck "shutter" under acceleration while this is happening, then smooth out when you drop below ~35mph? That would be another indictment for the UVCH.