Low boost

[Sting-Gray Neutral Pres.]

So yesterday I was driving a long distance on a slow highway with some traffic (50-60mph) and started noticing the truck was having trouble on cruise control...not accelerating in gear and resorting to downshifting. I used the Tazer's functions to bring up boost and I was only getting 1-3 psi while in easy cruise, and no better with no power or throttle response until it kicked down to 5th or so, got above 2500rpm, then would produce about 24 psi boost and rocket forward. Upshift and boost fell to low values again. RInse and repeat ad naseum until I got to my destination.

After being parked for an hour I started it back up and continued onwards. Drove completely normal from then onwards making 8~ish psi cruising in 8th and building boost with throttle while in gear, no longer requiring big downshifts to build boost. No CELs or on-dash errors occurred the entire time and operating temps were normal.

I read somewhere an active regen can mess with boost, is that the case?
What else should I be looking at or investigating? The turbo still spooled eventually and since it returned to normal after a system reset that makes me think nothing is wrong mechanically and something electronic was off. Variable vane actuator or something?

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[Rusty PW]

I've had a couple of vehicles do strange stuff. Shut them off and restart. And everything is fine. Never could find anything wrong.

 

[DylanM]

It kinda comes with the territory when so much vehicle function is software based these days. Reminds me of an old joke about if Microsoft were to make a car, it'd be considered perfectly normal to have it crash every so often and the owner would have to close all the windows, turn it off, then turn it back on in order for it to work normally again.

 

[Sbro2021]

You should be seeing Psi at the high end above 40 under heavy load and 25-30 the rest of the time your hear that turbo. (Verified multiple times with Jscan) VGT's suck ass!!!!! Give me back a spring waste gate all day everyday, at least it won't fail from some random computer gremlin...

 

[rharr]

Sorry I can't help you, but I got to do a forced rengen on the side of the highway yesterday if I wanted to go more than 30mph....

 

[22EcoDs]

The engine definitely responds slower when in Regen.

 

[Sting-Gray Neutral Pres.]

You should be seeing Psi at the high end above 40 under heavy load and 25-30 the rest of the time your hear that turbo. (Verified multiple times with Jscan) VGT's suck ass!!!!! Give me back a spring waste gate all day everyday, at least it won't fail from some random computer gremlin...

That's about 10 psi too high on both of those. You running a hot tune or something?

A little worrying that the ecodiesel brain trust is kind of collectively shrugging on this one. As dislikable as my old GM 6.2L turbo diesel was at least that thing would run on a single hot wire to the fuel cutoff solenoid.

 

[DylanM]

Do you have a scanner or some other method of checking for pending codes? Just because you didn't get a CEL doesn't necessarily mean the PCM didn't see something amiss, it just may have been something that takes more than one trip to kick out a hard fault.

IIRC, with a scanner you may also be able to see a counter showing miles since last regen. If so, that information could help confirm or dismiss a regen as a possible answer.

 

[Rusty PW]

Boost cut off is 30 psi.

 

[Sbro2021]

That's about 10 psi too high on both of those. You running a hot tune or something?

A little worrying that the ecodiesel brain trust is kind of collectively shrugging on this one. As dislikable as my old GM 6.2L turbo diesel was at least that thing would run on a single hot wire to the fuel cutoff solenoid.

No tune, bone stock. The boost is the only real reason the Eco soot machine makes the power it does. I'll gladly screen shot that boost next time I get on Jscan. I have to do an Intake replacement thanks to the EPA so I'll grab a screen shot. Also, if cutoff is 30 psi, Absolutely won't rule out Jscan not giving perfect numbers, as much of them are converted from whatever the computer output is to a number (American units ) we can understand.

 

[Sting-Gray Neutral Pres.]

Do you have a scanner or some other method of checking for pending codes? Just because you didn't get a CEL doesn't necessarily mean the PCM didn't see something amiss, it just may have been something that takes more than one trip to kick out a hard fault.

IIRC, with a scanner you may also be able to see a counter showing miles since last regen. If so, that information could help confirm or dismiss a regen as a possible answer.

I checked the Tazer for DTCs and there were none. Are these pending codes different than a normal DTC and if so do other scanners pick them up?

 

[DylanM]

I checked the Tazer for DTCs and there were none. Are these pending codes different than a normal DTC and if so do other scanners pick them up?

I don't know if a Tazer will display pending codes or not, I've no personal experience with one. Yes, pending codes are different than active codes or stored codes. Typically "scanners" or scanning diagnostic tools will be able to see and display all such codes, whereas your more basic code readers may only display active codes.

 

[Sbro2021]

You should be seeing Psi at the high end above 40 under heavy load and 25-30 the rest of the time your hear that turbo. (Verified multiple times with Jscan) VGT's suck ass!!!!! Give me back a spring waste gate all day everyday, at least it won't fail from some random computer gremlin...

To give my statement above as much validity as Jscan provides me, here are some screen shots this morning on the way through Denver to show some data around boost range. I pulled up a few metrics as I was looking for some other indicators related to my intake, I provided both the computer boost requested and actual as measured by the engine. It does hit 40PSi on hard pulls. Also at the top is throttle position as reference to how much boost the turbo creates at various positions. what I was looking for this morning was Mass air flow request to actual to help confirm why im getting P200a/b codes... plugged up intake for sure. Has a brand new air filter install 3600 miles ago so likely not contributing..
Anyway, here's some data points as promised:

And also, Jscan is Awesome!! Thank you Piotr Bialic for an awesome tool for us to use. Sure as hell can't get this kind of data from Jeep

 

[Rusty PW]

Mine will only push 30 psi. Don't know how you are seeing 40+.

From Goggle search.


The maximum boost pressure on a stock 3.0L EcoDiesel engine is typically around 28-30 psi, according to some Jeep Gladiator forum users. However, some users report seeing it reach as high as 30-31 psi. The smaller, factory turbocharger is more than capable at stock power levels, but it can be a limitation when pushing for higher horsepower.

More details:

• Stock Turbo: The 3.0L EcoDiesel engine uses a smaller, 41mm turbocharger.
  
  
• Factory Boost: The factory boost pressure is generally between 26-28 psi, though it can be slightly higher.
  
  
• Limitations: The factory turbocharger runs out of capacity around 300 horsepower.

 

[Sbro2021]

I dunno, I have an overachiever eco diesel I guess.. I would do a Goggle search too, but I search better when I'm sober...

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