I just picked up a 2003 F250 7.3 with 300k miles on it. It's my first diesel vehicle and I've been reading the forums to try and get up to speed on what to expect. On my first drive, I noticed the truck was supper sluggish - step on accelerator and it's super slow to gain speed. No fault codes or anything. I went after the easy stuff first knowing that the previous owner may have neglected it. Oil changed to T6 (5w-40: cold in CO), cleaned K&N filter, replaced fuel filter and EBPS and tube. I also checked the turbo wheel to ensure it wasn't loose, stuck, wobbled or anything.

I took it out for a drive and I noticed the truck takes a while to warm up. Idling there took more than 5mins to even move the temp needle a little.

While driving, I noticed the boost kicked in (whistling/whining) around 2000 or so RPM. Definitely no whistle/whine if you drove like a grandpa from a stop to 45mph.

I'm guessing I have a possible boost leak. Looks like I've got a lot of original vacuum lines. I researched how to do it, but I found myself a little stuck. Due to the K&N filter, I can't find the right size plug to the rubber coupler. I bought both a 3" and 4" PVC cap, but one is too small and other is too big. Anyone run into this and have a solution? I'm thinking of getting a 4" to 3" coupler which may be just small enough to fit the K&N rubber boot.

I'm really hoping to find a leak and solve this sluggish truck acceleration.

Thanks!

Pic of coupler - too big for 3" PVC cap, too small for 4" cap.

Pic of spider. Think the lower boot could have a leak?

 

Don't do it on the boot you have off in the pic. Need to do it on the backside of it at the boot going to turbo. If you do the one in the picture you will pressurize crank case to 30 pounds which you don't want to do.

 

100% what Tpayne621 said, I was planning to say the same.

You need a rubber coupler the size of the turbo inlet. I think it’s 3” for a factory turbo but it’s been a while. Be careful because the cap can blow out of the coupler when pressurized. They are easily made or you can purchase a tester from KC Turbos.
Watch the boot connections but also look at the plenums. Soapy water in a spray bottle can help.

Uppipes are a big source of power loss. Look for soot. I’d expect you to find some up near the back of the turbo. Cheap bellowed uppipes are a good solution.

Those “vacuum lines” actually carry pressure from the spider to open your wastegate when the solenoid tells it to. Many folks find it “unnecessary” and delete them.

Something else to check is if your truck came with a CAT. Those can get plugged up over time and cause huge performance issues.

Welcome to PMS (Powerstroke Modification Syndrome). Be careful though, the guys around here are always eager to help you spend money.

Here’s a video of a pressure test.
7.3 Powerstroke Good Boost Leak Test Reference


Edit to add: K&N filters don’t get much love around here. I personally detest them. Some folks love them. If you ever run across a used AIS filter grab it up. They were a factory upgrade and are awesome. This video will explain why I don’t like oil gauze filters.

 

Thanks! I meant to ask if I could do it at the boot leading to the turbo. Perfect. Let me give that a shot! Thanks!

 

Thanks for the notes! I also don't like K&N, but it came with the truck. They took out the stock air box so I'm stuck with this setup.

When you mention deleting the vacuum lines, do you mean you can simply remove those red and green lines without impact?

I saw videos of the uppipes thinking that could be an issue. The replacement didn't look quick. Definitely looked like an afternoon of f-bombs. I went searching for soot and surprisingly, didn't see anything that would indicate a leak. Is there an easy way to remove and replace those uppipes?

View rear of uppipe/turbo.

View towards / behind turbo

 

The red green lines allow the PCM to use boost pressure to open the wastegate. The wastegate is also mechanically activated. Folks will remove them to prevent the PCM from opening the gate this helping create some extra boost. It may be possible to get an overboost code or go into overboost defueling I running stock without tunes.

The easiest way to perform the mod is by just removing the red line from the gate and placing it onto a intake boot clamp to seal it up. Gate can be left without a cap but the red line needs capped to prevent boost loss.

A more “advanced” method involves removing the lines entirely. Put a small rubber cap with a little zip tie on the nipple at the spider. Place a screw or such in the intake boot where the green line is removed.

I also did not spot any soot in what can seen seen in the first photo. The second photo is of the downpipe.
Look well behind the turbo and down where they connect to the manifolds. Maybe you’re a lucky one!

 

Good idea to check for boost leaks! Anywhere around the boots under the spider or the plenums are typical.

In the pics the truck looks very original. Good find! And with 300k the OEM up pipes are surely leaking. It's a design flaw. One of your pics almost got it; put the phone close to the up pipe. Looking for soot on the up pipe blown down from the cast iron collector above. There is cheap short term fix but I recommend the cure, bellowed up pipes. And yes they can be a biotch to install.

For the air cleaner either keep the K&N and resolve to keep it clean, or switch to a 6637 kit.

 

Looking at that last picture showing the spider only shows the passenger side orange intake boot. You can see it's leaking at the top. I just tightened all the clamps on the 6 boots this Friday on the Excursion and the 2 orange boots were really loose and had the residue like yours. I've been having a whining noise in upper rpm and the truck would lay down if you put your foot in it when it got in the upper rpm. Truck now runs like a champ and expect the mpg to come back up as it has dropped off several mpg. Looks like a nice clean engine...

 

Always a good idea to check for boost leaks and do other maintenance items/mods, but I would add that these trucks are much different from gas engines. Without tuning it you have to get pretty deep in the pedal for it to feel somewhat peppy and responsive. It takes awhile to get a feel for them. If you're not about 3/4 into pedal travel don't expect much.

I'm not saying ​​​​​you don't have things to fix but what you describe sounds kind of normal for an untuned 7.3.

 

I agree with Kintla. These things are pretty lethargic stock. Get it ship shape, add a EGT gauge, and then a Hydra tuner. I can’t stand to drive mine without it.

 

Thanks for everyone's help so far. I pulled the boot today, but couldn't do a leak test due wrong sized parts. Picked up a 3" rubber boot from home depot and 3" PVC plug. I realized the turbo intake is smaller than 3". Opps! I should have measured before running off to HD. I ended up taking a few pics around the uppipe. It looks like the previous owner was in there, possibly removed the turbo and maybe did some work on the uppipe? The firewall looks to have been damaged by tools or parts. However, doesn't look like any soot there.

It's going to be below freezing here all week so probably won't get back to it until next weekend.

Thanks for your help and I'll be posting again next weekend when I can get the correct size coupler/plug.

 

Thanks! The truck came with a tune/flash - Superchips MAX MicroTuner. It was set for performance, but I reflashed it back to stock. I'm hoping to correct any issues and maintenance... then reload the tune. I set it back to stock so that I can use it as a baseline. BTW, no idea if this Superchips Tune is any good. It was just an interesting surprise I found in the glovebox.

 

Thanks! Do you just tighten them or would you recommend pulling them off to inspect/clean? I'm happy to just tighten, but would like to do it the "right" way.

 

I would start with tightening. Those boots can be a booger. Go ahead and make sure all of them are snug. Be careful, the plenums are sheet metal and can bend if you too rowdy with those. Let the leak test show you what to work on beyond that.

Still can’t see the needed area of the uppipes well enough for a positive determination. Usually leak at the section directly below the clamp. You’ll need to check both sides.

 

You have the correct boot for the 3" PVC plug. It's the factory turbo to CCV boot. The CCV is 3", spin the boot counter clockwise so the plug fits in. Don't go and pressurize thru the CCV mount tho. No need to go above 20psi