Erratic Boost/Possible Defueling While Towing

[JRJ04]

Yesterday I was towing about 3000-4000 lb with the truck listed in my sig. I was going into a pretty strong headwind and you could definately tell there was a load behind it. I had the tuner turned down on the 40hp tow setting just to be safe. I really had to get on it and hold the go pedal down pretty hard and long to get it moving. EGT's would occassionally hit 900 if i really really really held it to it.

The problem I had was when I was goin about 55 and wanted to punch it up to 70 or so. I was in od, and mashed the go pedal. Didnt kick out of gear, but the boost gauge jumped from about 6 to 10 really really fast. It climbed on up to past 20 and then started cutting out. I could hear the turbo spooling down and started to lose boost. I figured that was probably the factory computer defueling since I was getting close to 25lb or whatever the factory computer will let it get to. So, I backed out of it and just eased it up to speed.

Later, in the same situation, I was running about 6lb of boost and again tryed to lay into it and it got up to about 10lb and cut out again. sounded like it was defueling. could this be the transmission slipping? Tranny fluid temp never got above 160 and ambient air temp was about 70.

Sorry for the long post, but what do you all think that could have been?

 

[JRJ04]

anybody?

 

[iracemine]

sounds like your intake tube (part between intake filter and turbo) is collapsing under load. thats my guess.

if not that did you check all the obvious first??? fuel filter, oil level, blablabla....

 

[DaveBen]

sounds like your intake tube (part between intake filter and turbo) is collapsing under load. thats my guess.

I think you need to look at your answer. Intake COLLAPSING? No way without vacuum, and diesels of this year don't have vacuum in the intake.

Dave

 

[iracemine]

I think you need to look at your answer. Intake COLLAPSING? No way without vacuum, and diesels of this year don't have vacuum in the intake.

Dave

think harder..... there is a MAJOR vacuum in front of the turbo after the air filter its Saturday so Ill let this one slide

 

[JRJ04]

i have an upgraded air intake that replaces the intake pipe up to the ccv. its hard plastic...so i seriously doubt that 20lb of boost is gonna cause that to collapse. could it be the tranny slipping?

 

[BigDaveZJ]

Sounds like turbo surge to me.

 

[BIG JOE]

Sounds like turbo surge to me.

Me too JR. And a possible PCM driven, De-fueling. A fix would be to install a BPRV (Boost Pressure Relief Valve) in the MAP line ?

 

[JRJ04]

is it possible to experience turbo surge at just 10lb of boost? i could understand that at higher numbers, but not such a low one. isnt there a wastegate on the turbo that should release some of that pressure?

 

[BIG JOE]

is it possible to experience turbo surge at just 10lb of boost? i could understand that at higher numbers, but not such a low one. isnt there a wastegate on the turbo that should release some of that pressure?

Surge.. or IMO, more correctly described: Cavitation, is driven more by RPM than Boost pressure. Somewhere between 15 & 1800 RPM (depending on demands) the turbo compressor wheel can lose it's ability to maintain a smooth, even flow of compressed air. The reasons and fixes are many.

The Wast-gate, Wastes OFF any boost pressures over 16 to 20 pounds (a design parameter of Ford/IH), sensed by the MAP sensor. The MAP sensor opens the Waste-gate. When/if the Map sensor detects continued excessive Boost, it signals the PCM. The PCM then goes into a de-fuel mode by cutting fuel... in an attempt to reduce boost. The result is: a loss of power. A code can be set and the CES light can come on.

Simply Put.