Towing 36' Toy Hauler with 05 F350 Dually (65K Miles) with Tow Boss Package. Trailer ~ 15K. No Performance Mods!

Twice in about two years, towing the Grapevine Grade, I got a wrench and a PO234 code. BTW - I did have the famous oil cooler and EGR meltdown as 45K. All under warranty. Had New diesel proof EGR, new ARP studs, coolant filter, etc. installed plus all the stuff Ford did (new oil cooler, etc......).

I use a DashDaq with the Ford code reader to plug into the OBD II port. This is only systems that can customize how to read all the sensors - no mods or tweaks to the computer. I use to watch the EOT and ECT spread. My early warning system

It has a cool data recording feature. I went back and looked at the data and here is what I discovered

At about 43 mph I was nearing the top of the grade, never really getting on the truck very hard, that is when the code kicked on, max boost went to ~ 18 PSIG (Limp mode). It did easily clear by turning the truck off and on.

I was holding at 28.1-28.7 PSIG near the top and then it record one time a value 29 PSIG and that is when then code was tripped. BTW: EOT was 232 and ECT at 216. When climbing this is a typical spread. I get spreads on the down side cooling off where ECT goes down really quick and EOT is lagging. Those spreads are 20 plus. The truck never issues codes for that. Normal no load flat driving spread is 3, 5 or 8. No concerns about my oil cooler clogging up.

So in my mind 29 PSIG must be the limit Ford sets to prevent the heads lifting and all the other related issues (like CAC, blown head gaskets, etc.).

I would like to know two things:

1. Can anyone confirm 29 PSIG is the computer limit
2. What are the top items that might be allowing the boost to build to that level (maybe normal under heavy loads?). I climb for about 10-12 minutes max and never put the EGTs above 1150. That is about then length of time for worst case climbing.

Thanks for any guidance or feedback.

Mark

 

What is the MAP, BARO and EBP at KOEO? All should be very close to one another. Next check and clean the MAP hose and intake nipple ( MAP is located on the passenger side just above the evaporator housing ) and clean the EBP and tube that connects it to the drivers side exhaust manifold toward the front of the engine ( a piece of weed whacker line works well to clean out the tube, just make sure the engine is cool before you run the weed whacker line through the tube so it doesn't melt )

 

Can't confirm the 29psi limit, but I think the most common reason for over boost is sticking turbo. Either the vanes, unison ring or the valve and linkage.

 

The computer is going to have a code set based on a strategy of boost vs expected boost vs other sensor readings like VGT and EBP. It probably isn't as simple as 29, oops, code. If you really weren't getting on the truck very hard it should have only had around 20 psi boost. I only get up to 28 with full throttle and high rpm on a hard hill with a heavy trailer, other than that it's quite hard to get.