Howdy Folks.

I've been a long time user of this forum for at least the past few years to help me solve a myriad of issues with my small fleet of Ford trucks. Thanks to all for that.

Now I have a problem I cannot seem to find addressed in here before and figured maybe it was time to join:

Issue: 1995 Ford F350 dually 7.3l powerstroke 340K km has little towing power and upon anything other then the most gentle acceleration, exhaust discharges from the air filter and overall fuel mileage has noticeably dropped. While driving there is also the odour of fumes in cab. There are no issues starting cold or warm and no noticeable exhaust leaks when idling.

Is this simply an exhaust manifold gasket issue? Any advice before I start ripping things apart would be greatly appreciated.

 

What do you mean by the exhaust discharging through the intake?

If you are letting off the throttle when it's at high levels of boost the excess air will escape back out the intake, but it isn't "exhaust". These trucks don't have a wastegate so there's nowhere for the extra pressure to go but back out the intake. Nothing wrong with that, just how they work.

Bad mileage could be injectors, injector o-rings, bad HPOP, plugged cat, dirty air filter, dirty fuel filter, plugged FPR screen, bad fuel pump (fuel pressure too low)...

Exhaust fumes in the cab suggests either leaking turbo o-rings, leaking up-pipes, leaking exhaust manifolds...

 

When I start the truck and tap the accelerator there is a noticeable discharge of smoke (exhaust?) coming from the air intake. When I drive the truck and accelerate you can see the smoke coming from under the hood. All other times there is an ordour of diesel exhaust in cab and I have to drive like Ace Ventura.

The gradual reduction in fuel mileage and the gradual increase in the exhaust problem appeared about the same time so I thought they might be connected. Fuel and air filter were changed out recently.

 

Sounds like a bent exhaust push rod ...

 

That's an interesting thought (and I hope you're wrong) but there is no unusual noise coming from the engine and I'll bet it's been driven at least 5K since the problem started to develop.

Shouldn't you hear something if it were a pushrod? Wouldn't it have broke apart by now?

 

What else can it be ?...

 

Something easier to work on ?

I just figured there would be some sort of noise.

 

Wouldn't this be simply a case of whatever partition there is between the exhaust side and intake side of the turbo being blown out? That would send exhaust gas straight through the intake, wouldn't it? Heckuva way to create an impromptu OBS EGR valve.....

Or maybe a crack in the turbo pedestal?

 

A crack in the turbo pedestal would just leak oil.

 

After thinking about it , maybe a bad valve ?

 

A bad intake valve would push unburned fuel-air out on the exhaust stroke, and would only be one eighth of the total amount of gases going in or out. It would likely NOT be exhaust gas, because if that valve is broken or stuck, there's no compression in that cylinder, thus no combustion, and the fuel-air wouldn't be burned. I would think that for it to be enough to be noticed, several intake valves would have to be compromised, and the engine would probably run like cr@p.

My money's still on a breach between the exhaust and intake sides of the turbo. I wonder how loud the truck would be with the up-pipes disconnected from the turbo. A BRIEF test with them disconnected, to see if the discharge issue persists, would rule the turbo in or out.

 

Could be a serious blow-by issue as well and the smoke he is seeing is coming from the CCV.

I suggest you pull the intake elbow (aluminum piece) off the truck and see whether the "exhaust" smoke comes from the inlet of the turbo or the little hose coming out of the Crank Case Breather that sits on top of the driver side valve cover.

Or for that matter, you can just open the oil filler cap and see what kind of smoke and pressure you're getting from there. If you turn the cap upside down and sit it on top of the hole in the valve cover there should not be enough pressure to blow the cap off the hole. The cap should just slowly kinda vibrate off. If there is enough pressure to blow the cap off, you have an internal engine problem somewhere i.e. a hole in a piston, or badly blown rings.

Maybe you'll get lucky and it is just something simple like a blown up pipe gasket...

 

I'm with Nate on this one. At least try these couple things. They're cheap and easy and will eliminate some possibilities.

 

Also my first thougth was blow by issue, but Im not a mechanic and I havent heard that the rod or valve can cause that, so lets see how it goes.

 

Aren't you a human mechanic Jose?