boost issues..

97cherokee · May 15, 2021

so i have a 14 6.7 that intermittently has issues with building boost, i have converted it too a 2015 turbo setup, it was doing this intermittently as well with the old turbo. so what it is doing is i can crank the truck up cold, run 5 minutes too the gas station, shut it off. come back out and leave and it wont build any boost, black smoking (******d with proven diesel tunes) did it with the old turbo and stock ****** hs tunes as well. any how get going a bit, mash the throttle a few times and itll start building boost fine and typically be fine for the rest of the drive, although sometimes itll quit building boost while driving. im not having a cel pop up at all. truck has a new exh gas psi sensor at the time of turbo change, newer boost psi sensor and newer map sensor as well.

thanks for the input!

Sterling6.7 · May 15, 2021

Have you checked the intercooler piping? MAF sensor? Muffler bearings ok and blinker fluid full? Stock air box?

6.0 Tech · May 15, 2021

Typically a small boost leak will cause this, possibly an exhaust leak as well. These rely heavily on maf/boost readings for fueling, and if the numbers don’t match what they want to see it will cause the computer to go full retard and fix the turbo vanes in one position until it feels like it’s reading right again.

Also seen a lot of these where the gears will stick in the vgt actuator, and sometimes unplugging and plugging the vgt actuator in several times while running it at 1200 rpm or so will unstick it. Sometimes it requires a whack or 2 to the cylinder looking thing across from the vgt actuator on the turbo. This is where the oil plunger and gear train is and typically will unstick it as well. This is a lot easier if you have a piping kit.

StrokedKR · May 15, 2021

Start with cleaning the MAF sensor.

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97cherokee · May 16, 2021

so the turbo is a brand new motorcraft 2015 plus. and ok I will clean the maf sensor, it is an aftermarket and not motorcraft one... guessing I should just buy oem? it did fix a cel it was causing a while back.

no charge air leaks or exhaust leaks, has an s and b cold air intake with afe charge air piping.

StrokedKR · May 16, 2021

The MAF resistor/sensor works on hot heat loss generated by air flow. If it is dirty/oily it will skew the reading, affecting air/fuel ratio.

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97cherokee · May 16, 2021

I removed and inspected it, it was clean and dry, I know for a while when the old one was causing a cel I left it unplugged for a bit. I'm going too leave it unplugged and see if it still does it. if I remember correct now that I think about it, I believe the issue got worse with the new sensor but no cel. so I may wind up getting a new one, any brand recommendations? thanks again.

sootie · May 17, 2021

It is by chance very humid when this occurs? Sounds a lot like poor MAF scaling in the tuning. Or a bad MAF sensor, or the vgt not actuating correctly.

97cherokee · May 18, 2021

I dont quite recall specific OAT or humidity, have been running truck with maf unplugged for a few days and havent had any issues yet. with it unplugged I'm sure it sets too a default in the pcm

97cherokee · May 18, 2021

also truck did this with 2 different turbos and sets of tuning, currently have a new ford performance 15 plus turbo and proven tuning, did it with an HD minimaxx and stock 14 turbo as well.

97cherokee · May 23, 2021

well so far a week or so later with the "new" maf sensor unplugged and ive had no issues going somewhere, shutting the truck off and then going somehwere else a few minutes later, seems too me that the new sensor is bad. thoughts? thanks!