My family has a 2000 F250 with a 6.8L V10 automatic and about 140k. We bought it in 2004 with about 100k, and it was a great truck for many years. However, several years ago, we noticed a slight loss in power going uphill, even without any load. Over time, this has gotten worse, to the point that the truck lugs and often needs 2nd gear for even slight grades...EMPTY! It also pings badly if we run anything other than premium gas(supposed to be able to run regular). It is rated to tow 10,000, but I wouldn't want to tow anything more than 3-4,000 like this. Truck is in good shape otherwise, everything works well. A couple people suggested the catalytic converter may be plugged, but a shop checked it with a pyrometer and said it's fine. Several different mechanics agree that it should have more power, but cannot find the cause. Anyone have any suggestions/ had similar issues?

 

Hook it up to a code reader first to see if there are any pending or stored trouble codes that may not have triggered the CEL yet.

 

Look for a vacuum leak.

 

Plug wires and plugs (after checking for vacuum leaks). Fuel filter(s).

 

pull that CAT and put a test pipe in. I bet you dollars to doughnuts itll run like it should. then, to be legal, replace it, of course. pyrometer isn't gonna tell you the whole story. mine ran fine until you put a small load on it. was always worse at hiway speeds, and the ping is the give away.

 

Do that. ^^^

 

Question? Why would a bad cat cause pinging?

 

Because it increases cylinder pressure and temperature, causing the fuel to ignite prematurely.

 

I'm not one to point a finger at plugged cats, as it almost never happens and the symptoms are almost always caused by something else... But on re-reading your first post, it is possible.

I would hook up a vacuum gauge. With the engines warned up, look at how much vacuum you have at idle, then run the engine up to about 2500 RPM (no load, in neutral in the driveway) and hold it there for a few seconds..

If the vacuum drops significantly, look at the cats again. If they are not clogged, the vacuum should go up slightly at higher no-load RPMs.

 

Yes, failing CAT. Same thing happened to me on an F-150.

Disconnect the exhaust at the Y pipe and take the truck for a quick (loud) spin. You will know right away if you have a bad cat.

 

We used to drill a hole in the pipe before the CAT, it'll let the pressure out if the Cat is plugged and you'll see power increase.

 

Great idea.

I would avoid this, rather than drilling a hole remove the oxygen sensors and drive it around, will be about the same thing.

 

Yeah but depending on how long the sensor has been in place, be prepared to buy a new one because it may get destroyed trying to remove it.

 

i agree with that !

 

Do come back with the solution, when found.