2973 help

[dieseltek8080]

So I Have been racking my brain on this one. Any help is appreciated.
2008 871 isx.

customer brought in with complaint of power surge. like on off switch throttle. Truck has 500k on it and has owned for 150k. Been to countless parts changers and wound up at door. multiple times has new tps and imap sensors. tps was easy as I found signal wire to sensor 2 broken causing 0 to 100% as soon as throttle was touched.

now code 2973 has been a chore. found CAC cooler broken at multiple tubes and went from 30 psi to zero in less than 2 seconds during pressure test. has new CAC now. No more cold side leaks. now mind you this truck has been EGR and DPF tuned by another shop to try to repair this truck. So I am a bit in dark as to who tuned it and physical mods done. All I know for sure is egr cooler still present and flows coolant per infared temps but exhaust part is cold and has block off plate sandwhiched where egr elbow meets intake..

1 imap is new from less than 100 miles and have previous supposed failed sensor... no soot because no egr and all readings same between the 2.

2 baro reads within 1 hg of local

3ohmed turbo speed sensor. 890 ohms.

4 checked air filter.


now data on snapshot

exhaust pressure 129.17 Seems legit for 100% throttle

1725 rpm

exh calc temp 298 pyro around 800

imap temp 62 degrees
imap press 52.3


89%load

vnt 33 % closed (measured)

turbo speed 99242



this truck drops off between 1500 and 1750 in high gears. noticeable surge in power. after 1750 clears up.

built 38 pounds of boost until surge and drops to 28 to 30 and stays there until next shift.



What am I overlooking? I am installing sight glass on return to verify good orings but the code is generic. its sayin pressure is above or below forcasted pressure for current conditions but I don't know if its high or low... Any help is appreciated. need any more info from snap shot just ask.


cheers

[dieseltek8080]

Well it appears I may have found the issue... lots of micro bubbles in return line. none in suction. erupts with air at 1500.... so my guess is the injector orings failed and compression is aerating fuel rail and the ecm is seeing numbers off.... howevwer please direct me to what is off on data I wrote. ill throw injector orings in and retest.

[Rawze]

did you do an injector leak test?

[Marajin]

Check to see if it has an after-market CAC unit on it like a duralite etc. Those things cause a lot intake flow problems. Nothing but restrictive crap junk. Stick to OEM CAC units only.


FC2973 - Intake man pressure data erratic, intermittent, or incorrect. <= this can be a tricky one ...

> Another bad sensor.

> Wiring issue with imap, crank case pres, exhust pres, sensor etc.

> after-market CAC restricting air flow

> Maybe large CAC leak

> Restriction from device installed inside the intake piping between the CAC and the intake manifold. Seen this more than a few times.

> Some model enigne will also compare the imap pressure readings against the exh. bp sensor and/or the ambient (or crank case filter sensor). etc. Make sure all those sensors are up to date and have been replaced too. not just the imap.


==

It could be fuel related but what you describe with the turbo dropping back sounds just like classic symptoms of engine silent derate more than anything else.

If it has a bad delete program in it then there is no telling what corrupt damage programming the ECM is having to deal with. Delta-P sensor or some other egr sensor may have gone bad and is getting it into a derate if the del programming is crappy. Bad del shops are everywhere like a bad plague. I have seen delta-p sensor on both factory stock trucks and bad delete cause engine to completely loose throttle response randomly or have large hesitation at take-off or less power at higher rpm. even make derates and force boost to drop back just like you describe.

You say it is 2008. 871 - this would mean it has or had a doc-dpf can too. Most guys who do deleet will not hollow cans properly. They do stupid sh$it like only make a bunch of small holes in them and later you get a lot of reflected heat that damages injectors and causes other engine problems. They ere too dumb to know that it is heat you are trying to let out not so much air. Anything heat can bounce off of or get absorbed by in exhaust is bad for them.

You never did say what kind of truck, etc. -- or who did the mods/dleete to the engine. A history alway helps. Maybe also list all the other codes is having including inactive.

[Marajin]

(02-17-2017 )dieseltek8080 Wrote:  ...
tps was easy as I found signal wire to sensor 2 broken

...

very common issue with pete and kw trucks. Oddly enough, replacing the sensor always clears up these sort of issues but comes right back after a while. It makes it seem like you keep getting bad sensors but the problem is actually something else.

it is quite often a a ghost of cab plugs, but no one believes it until they take the time to clean em up and re-seat them.

Here is some details Rawze on the discovery of this. i asked him to go get from the old forum and re-post it.
http://rawze.com/forums/showthread.php?tid=1481