truck cutting out

jwlandry · Dec 15, 2013

Since ive done my s366 at 25-30 lbs of boost it feels like the truck starts cutting out. Idk if its defueling bc of boost of if its some other issue. It runs great except for then.

Any ideas?

JD3020 · Dec 15, 2013

Did it do it with the D66? Its very possible the PCM is seeing overboost and cutting fuel, although it seems to be rare for OBS's to do it. Or it could be the HPOP dropping pressure and causing it to cut out.

jwlandry · Dec 15, 2013

Never did it with the d66. The t500 is holding the pressure.

Everything seems to be normal except for it cutting out.

If i unhook the hose running from the map sensor to the Y would that prove to see if that is what my problem is? I know it will throw a map code but would the code make the truck not build full boost?

jwlandry · Dec 15, 2013

Just pulled codes...

P0478 Exhaust pressure control valve high input - Plugged sensor line, stuck butterfly, restricted exhaust

P0236 Turbo boost sensor A circuit performance- Restricted inlet/exhaust/supply hose, missing hose

P0238 Turbo boost sensor A circuit low high- Circuit short to power, MAP sensor

JD3020 · Dec 15, 2013

jwlandry said:
Never did it with the d66. The t500 is holding the pressure.

Everything seems to be normal except for it cutting out.

If i unhook the hose running from the map sensor to the Y would that prove to see if that is what my problem is? I know it will throw a map code but would the code make the truck not build full boost?

With the hose unhooked it shouldn't build any boost at all. You could try unhooking the sensor itsself and driving it, but last time i tried it, the truck freaked out.

I'd get a boost fooler, and maybe try to get your hands on another good MAP sensor to see if that helps any. Odd that its only doing it now, if it is boost related.

Also, hows fuel pressure?

jwlandry · Dec 16, 2013

68-65 psi

JD3020 · Dec 16, 2013

Is it holding steady when it cuts out?

jwlandry · Dec 16, 2013

yea. everything does. Fuel pressure and icp.

It has to be due to boost.... I can run it up to 20-25 but once i get close to 30 it acts up. Go back to 25 and it good to go.

I cleared codes last night and drove it today. Still no codes. I didnt get out the tow tune either so it never got higher then 20-22 lbs of boost.

m j · Dec 17, 2013

sub'd

95-F-2FITTY · Dec 17, 2013

sub'd as well

Rideracelivemx7 · Dec 17, 2013

my truck did the same thing when I swapped from my 95 PCM standard to 96PCM auto and as soon as it hits 25PSI it violently cuts out lol but then again when you have this set up hitting that hard it guess it will do that. Simple solution, go to homecheapo and get an air compressor regulator for like 12$. set the gauge itself for like 30psi as it in turn lets the PCM see about 22 it think it was?

If you set the air regulator for the actual 25psi the computer only sees ~11-12PSI. ask me how i know LOL no wonder why i felt like it had low power...

i tried the dieselsite boost fooler and i felt it made the truck loose power compared to the regulator i have in there now.

jwlandry · Dec 17, 2013

i built me a home made fooler and set it with the air compressor to between 25-30 and its still cutting out just doesnt seem to be as harsh as before. Gonna mess with the regulator some more and see if anything changes. I watch the boost gauge good this time and as soon as 30 lbs is hit it starts cutting out.

Plus side is that it didnt throw no codes when it hit 35 psi. I just dont want the cutting out to mess something up.

bucklee00 · Dec 18, 2013

Is there a way your tuner could disable the stock defuel on high boost?

m j · Dec 31, 2013

IMO it isnt a defuel like the SDs
the stock MAP on our OBS reads to 36psi according to info I found, I can watch mine to 30+ then it goes a bit nuts and truck bucks
seems we push the map out of its range and it starts sending weird numbers

I am goin to try the pressure relief valve idea like seen http://www.dieselsite.com/boostreliefvalve.aspx

they are available for under $10 in the US
http://www.amazon.com/gp/product/B007GDXT3O/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

lincolnlocker · Dec 31, 2013

m j said:
IMO it isnt a defuel like the SDs
the stock MAP on our OBS reads to 36psi according to info I found, I can watch mine to 30+ then it goes a bit nuts and truck bucks
seems we push the map out of its range and it starts sending weird numbers

I am goin to try the pressure relief valve idea like seen http://www.dieselsite.com/boostreliefvalve.aspx

they are available for under $10 in the US
http://www.amazon.com/gp/product/B007GDXT3O/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

Imo, those act as a boost leak.. use a regulator like riffraff and some others do...

live life full throttle

m j · Dec 31, 2013

you dont buy this bit?

The regulator actually robs some of the pressure in order to open - as shown above(cracking pressure). At low boost numbers the two gauges will never give equal readings. You will eventually reach the set pressure(in this case 22 lbs.) under full throttle, but a regulator is much slower than the instantaneous response you see when using a BRV+. A regulator and a BRV will show the same max HP figures on a dyno because you run on a dyno at full throttle and max boost at the MAP sensor is already reached before you start taking your readings. However, throttle response on a truck with a BRV+ will be noticably quicker. Again, response is INSTANTANEOUS with a BRV+.

We decided to post more actual boost numbers with our BRV+. We run 2 boost gauges into the BRV+. This allows us see what the BRV+ lets the Map Sensor see as well as actual engine boost.

Here are the details on recent testing done on our 1999.5 PSD:

At anything under 22 psi boost on the main gauge, the Map sensor sees exactly what the engine sees. For instance: at 15 psi of boost the map sees 15 psi - At 22 psi, the map sees 22 psi. But, even at as high as 54 psi boost, the map sensor still only sees 22 psi. We can see 52 lbs. to 54 lbs. of boost on our company truck under the right conditions. We run the same boost relief valve we sell - nothing more special. We do NOT get a SES light. We see 22lbs maximum at the MAP sensor. The BRV+ will definitely eliminate issues from overboost in trucks getting over 25 lbs. of boost.

lc tpi · Jan 2, 2014

i have close to the same setup as you do . my truck is an early 95 and with the 366 238/100 injectors and gearhead tunes i thought it was the rev limiter. i put a boost fooler on it and no more cutting out. mine was bad it was like a missfire on a gas rig . i would see 30 psi of boost befor it would do it and it would not throw a code? and i did check and the cel works, go figure,.

jwlandry · Jan 8, 2014

My problem was tuning related...... I think.

Turbtators · Jan 9, 2014

Did you ever find out what the issue was for sure? I just had a similar issue as you described I'm just not sure what psi it was at. Then I got this cell shortly after P0238 Turbo boost sensor.