Boost, then way low boost

[6speedsd]

This is driving me friggen nuts. When the truck is cold, everything works as it should. Boost is where it should be, both during accelerations and while cruising. But this only lasts 10 mins or so. Once it warms up, boost is like 5psi low across the board. 5 is not an "exact" number, but very close, and always consistent. 65mph cruising, I see maybe 2psi. Long hill, you obviously hear it spool up more to maintain speed...maybe get to 6-7psi. Have to punch it hard to get over 12psi on acceleration from a stop. WOT I see 25psi max, and anything over 20 it fluctuates up and down 2psi. This issue screams exhaust leak, but I have yet to find one. Had a small uppipe leak at one time but that's fixed. No soot now around any connection. Pressure tested IC today just for grins...holds 25psi with no leak down. Both IAT sensors are new, new EBP sensor and pigtail, within last 5000miles it has had new uppipes, turbo, all 4 boots, TC. All readings are normal. Nothing stands out at all. I know some will say check all the obvious (EBP tube, map line, etc). No need for that. I've been over everything I know to look at, and everything is as it should be. Seriously tired of fooling with this issue. Been ongoing for quite some time now. Any other idea that I could be overlooking? Oh, tuned or stock it does this. Just don't understand why it is fine until up to temp, then starts this garbage.


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[swinky]

High pressure oil leak I'm guessing. What's icp/ipr like? Does it start fine when hot?

 

[6speedsd]

Thing runs like a top. Got all the updates when I studded it (same time new turbo, etc went on). No HPO issues at all.


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[Twinboys]

How do you know you don't have HPO issues? You can not know without monitoring the icp and ipr numbers.

 

[6speedsd]

Because I monitor my ICP and IPR numbers. Just didn't write them down the other day., and my memory sucks. But, If it makes you feel better, I've never had a starting issue...fires right over hot or cold. IPR is low when cranking like it should be, ICP is 600ish when it fires.

I'm no idiot when it comes to these trucks. When I say I've checked all the usual, obvious culprits of low boost, I mean I've checked them all.

Don't mean to come across as an ass, but that was sort of a smart ass reply, with you basically assuming I didn't know what I was talking about....and I've had a long weekend, and I'm tired and cranky. Lol


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[Twinboys]

You didn't say, I didn't know you were an expert, and I was trying to help someone who I thought might be assuming too much like I have done myself. I won't make that mistake again. Good luck.

 

[sootie]

quite often low boost on a six oh can be related to an HPO problem. are your egts low also?

 

[6speedsd]

EGT's are normal during every day driving. Towing they are slightly higher. If I get above 65mph thy hover around 900-1000, but 50-55 it'll climb past 1200 quick tying to maintain that speed on hills. Talking maybe 7-8k behind the truck. From a stop, it rarely breaks 1000 with that load behind me until it shifts to OD/locks TC, then it'll climb fast.

I don't understand the surging above 20 psi though. It's like as soon as the gauge hits 20, it'll surge up and down 2-3psi. Anything under 20 doesn't do it. I'm off today for rain, and if it'll ever stop, and the kids go down for naps, I'm pulling the turbo and resetting it and the ypipes just to ease my mind about a leak. Even though I've done it 3 times now. Just haven't completely pulled the turbo and started over.

Side note....at one point yesterday, while towing that load, thing just cleared up. Boost was up where it was supposed to be. Stayed that way until I pulled off at an exit and stopped at a traffic light. Then it went back to crap. 5ish psi low. This thing running 5psi low while pulling a trailer around sucks.


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[6speedsd]

Turns out I did have a ypipe/turbo leak. Was leaking down on the back side where I couldn't reach. Once I pulled the turbo you could see where it had leaked. Got that lined up good this time, and readjusted everything. Haven't taken a drive yet...been too busy. Will know tomorrow if it's fixed. Explains the surging pressure, but not why it just randomly cleared up yesterday. Oh well...we shall see.


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[6speedsd]

OK let's revisit here. Still fighting this issue. Ypipe leak is sealed finally. Watched some numbers today with Torque Pro app. My HPO system is plenty healthy. Numbers look good there across the board. Here is what threw me. MAP and boost were identical all the time. If boost was 5psi, map was 5psi. Isn't MAP supposed to be atmosphere plus boost? Need to check it koeo and see if it, baro, and ebp are reading within .5 like they should be. MAP sensor is about the only one I haven't replaced. Ebp and pigtail got replaced when I had it tore apart last fall. Should I be looking into a MAP issue, or does torque pro read it different than say AE?