2006 E350 6.8L V-10 157,000 miles

I am about to take a 2500 mile drive and this appears in the last 2 tankfulls.

I have had a sudden decrease in MPG going from the normal 10 mpg, down to 7.5 mpg. I'm currently monitoring the 3rd tankfull.

I just found that the 4th exhaust stud or bolt head bolt snap off on 3 ports on right side. The left side there are also 2 bolts snapped on 2 ports.
Currently I do not hear any loud exhaust leaking noises. I have not had any CEL check engine lights or error codes shown on my ELM code reader.

Obviously it needs to be repaired and will do that soon, but I was curious if it would or could affect the lower mileage numbers.
There are so many sensors telling the computer what to compensate for, I wondering if the manifold leaking would throw things off and cause the engine to consume extra fuel.

I just had a bid from a local company that only services vans, and mostly Fords, to fix the studs, charging $1000 just to R&R the engine, plus the unknown amount of whatever the materials and labor is for the stud repairs.
This is not a job I would want to tackle myself. I'm too old. (smart).

I will head back to the shop to get the engine checked out this week.

 

When is the last time it had a tune-up? Fuel, air filter. Plugs and cops? I take it no check engine light? Could be a slight vacuum leak. If you can't hear the exhaust leak then it shouldn't be enough to affect the engine or mileage.

 

Yes.
It sucks air after combustion and before the O2 sensors.
The extra air tells the O2 sensors it's lean so the computer fattens up the mixture.

 

Plugs done at 100K miles
K&N Air filter done after first sign of milage loss. (2 tankfulls ago.)
Fuel filter is due. It has been a while. No stumbling at the highest rpms.
I'm certain the right side exhaust is leaking at the manifold. There is a small amount of black discoloration at the gasket area. It is just not loud.
Cops? Probably originals. No CELs.

I am hoping to get the vacuum system checked this week. It could tell me a lot.

 

Bingo.

Don't waste time chasing other possible causes. Fix this obvious problem, then see if there are other problems that need to be solved.

 

This obvious problem isn't a cheap fix and I'd want to know for sure if it was the culprit. If you could have the dealer or a good mechanic put it on the computer and see what the o2 sensors are reading to see if there is a lean condition causing the mixture to fatten up. Not sure how feasible that is.

 

I would think on a van , with the dog house off , you have more room than a truck to repair the broken bolts .
A thousand dollars seems out of line .

 

That would be relevant if fixing the exhaust leak were optional, but it's not. That kind of exhaust leak will not pass inspection in any state that has any kind of safety inspection, and it can trash your valves, too. Since it's not optional, get it done now. It's almost certainly the source of the problem, and even if it's not, it's clouding the issue, making the diagnosis more difficult.

The only way to be sure is to fix it.


That's easy. Most chain auto stores will read codes for free.

Better yet, get one of these and log your engine condition while you drive: Obdlink

Log to your laptop or smartphone (Both computer and phone software is included in the purchase price.) Review the logs at your convenience. See lots more information than you can with just a code reader.

 

Thanks to all that have added information on this issue.
I do agree with fixing the obvious issue before moving on to the unknowns.

I stopped by the repair shop today and spoke with the new service dept manager about the symptoms I am having. His reply was "the leaky manifold will cause the O2 sensors to respond incorrectly causing a rich mixture".
His new "really rough" quote was $1500 - $2000 to replace all of the studs depending on how much drilling they may have to do. I left not feeling real comfortable with the price quote. His shop now also handles repairs for imports.

There is very little room to work on the V10 engine on the econoline vans, even with the doghouse cover off. I can understand the possibility of needing to remove the engine to be able to access the studs, broken or not.

My first opportunity to drop off the van for repair is in about 6 days from today, August 22. I will update this thread as I progress.

 

Somewhere on Youtube I saw a video about replacing engines on E-series vans. Though it's not 'by the book', this shop found that lifting the body was actually quite a bit faster than pulling the engine in the conventional manner.

If I ever have to pull an engine, I'm going to look very closely at that method. You might want to look up the video and suggest it to your shop.

 

I use the Torque ap and a $10 blue tooth adapter to look at O2s and short and long term trims.

 

I would check fuel trim. Just curious are you traveling into western states with heavily fortified ethanol fuel?

 

Well after pulling the engine out of the van, the easiest way to remove those studs is by welding a nut over the stud, then unscrewing the whole stud/nut, not by drilling and running the risk of damaging the heads. Once that happens you might need helicoils to fix the heads, assuming they're not damaged beyond repair. I would look for another shop.

 

 

Wrong again. Nothing new about that.

Just because you don't think it caused you an MPG problem doesn't mean it can't cause and MPG problem.