Surging 2001 7.3

[Jim Culver]

About 3 months ago (warmer weather) I bought a 2001 F-350 Crew Cab LB 7.3 Auto 4x4. From my experience with my '85 ATS turbo 6.9, I had the 7.3 muffler removed making it straight 3" exhaust. Other than a K&N type (panel) intake filter it's stock.

Since the cooler weather has begun (KS) after the engine has started just fine (idling) you begin to hear the waste gate opening and closing sounding like a 'blow torch' (not cool for the neighbors @ 6 AM). One I touched the accelerator it was fine for a little bit, then the cycle would start again. Once driven it was fine.

Now with the OAT in the 20 degree range it does the above plus the engine & truck surges (approx 200 RPM). Not good.

A chat with a local dealer mechanic suggested I might want to replace the Exhaust Back Pressure sensor (4C3Z-9J460-A, retail $138.00), I bought one but decide to write you guys before I swapped them out. The mech explained this sensor reads the pressure between the engine and the turbo, and didn't really think the **** removal was a big factor. He also said he did some other work on a truck that did the cycling but didn't surge and the customer didn't complain about it (it's **** was removed). A buddy who had a '99 that he had removed the **** on cycled like this.

Help, my fellow 7.3 brothers. Not gonna do this much longer.

 

[jharvey]

Jim I'm not sure on this as my 7.3 was a '95 and didn't have a wastegate but the EBP sensor sounds like a good start.

Start with the easy and work into the expensive

John

 

[wanderer]

Not sure if I'm calling this right, but the surging is probably the IPR. Pull it, clean it, install new o-ring. Surging gone.

 

[24VChevy]

There is a warm up valve behind the turbo. It closes to help warm the engine in cold weather. It will cycle off with throttle or stay closed (on) if left idling. You can disable this by unplugging it. It will set a code but not a CEL. The plug is infront of the turbo under the compressor dischage. It is a two wire connection plugged in at the base.

 

[Doggy Daddy]

It sounds like the EBV (Exhaust Backpressure Valve) or "warmup valve" doing it's normal cycling. It has some parameters to cause it to operate at idle: air temp below 40*F, accelerator at idle, parking brake applied, Park/Neutral on autos and clutch pedal in the up position on manuals and no service brake applied. On at least some of the calibration codes it will cycle on while driving with light accelerator settings and disengage when more accelerator is applied; that sounds like the surging you are getting?

I thought it was a PITA and disconnected mine at the air temp sensor on the back of the air filter box. I never had any problems with it being disconnected although our winters only occasionally go into the 20's.