Hey guys- Long-time reader, first-time poster...

I am having an issue with my 2000 F250 SDTY, that I hope someone out there might recognize and have a solution for.

I have roughly 115,000 on my V10 (second engine in this truck, 226,000 on OD). Recently I've seen that after the truck has been running/working for a few hours and gets heated up, that it starts running terrible: rough at idle, intermittent "missing", I can actually smell gas in the cab like it's fouled or flooded, and when I am running down the road there is no power- I hit the gas, it downshifts on cue and promptly begins to slow down as the engine is revving near 3,800 RPM or so. When it finally does shift into the higher gear, I can actually get it to backfire. The whole truck literally shudders and shakes during this "shifting" phase... and you can forget about gas mileage- try 5mph or less!

I have had it into Ford twice in the last 60 days and the only thing they can come up with was that my PCV valve was stuck open. They replaced it. That didn't fix it.

Both times they had it while it was acting up, and could not find any definitive problem.

Here is what I know:
-The CPU is not throwing any codes anywhere, engine or tranny
-Ford put my truck on their "Power Balance" machine and the diagnostics came back as follows:
~Fuel injection pressures all at acceptable levels
~All cylinders firing normally, without incidence throughout power band
~Heated Exhaust gas sensors working
~All COP's firing normally
~The MAF sensor is not faulty
-Same issues prevail whether the CAT is connected or not- originally I suspected that as the truck heated up under workload, that the CAT was somehow choking the exhaust flow, thereby fouling the engine... this is not the case.

Basically while they are looking at it, my truck is running in excellent shape!!- "and making power just as it should, especially given the mileage on it..."

Early on I thought that I had faulty COP's- the Coil-On-Plug's were changed out by Ford back in March, along with new Motorcraft plugs- but, again they appear to be in good working order according to Ford...

It's not water in the gas, I have tried running succesive tanks with Iso-Heet... nope.

Ford can't isolate the problem and I am concerned that I may be doing more damage to the rig by driving it like this, but my options are limited when noone can figure it out.

The only thing that I can figure is that it is possibly either a bad/faulty/OLD fuel sending unit (inside the gas tank?) that starts acting up after being run for several hours? OR, the CAT is the original CAT that came on the truck 7 years ago. It has 226,000 miles plus idle time on it. I removed it back in March, when I was diagnosing the COP issue then, and cleaned out those loose baffles that I could get to easily enough- I thought I cleaned it out pretty good- Are these engines so fine tuned that a partially, or completely, hollowed out CAT would create issues like this?? Again, these problems really only present themselves after the truck has been running for several hours.

I own a commercial snow removal company here in Alaska. My truck is the first one out and the last one back in, and I know that I have put some hard miles on it over the years, it kills me to have it running like this without having a solution!

Your help and suggestions are greatly appreciated, Thanks in advance!

 

The symptoms sound exactly like my problem with the plugged catalytic converter, down to and including the smell of gasoline, the backfire, the downshift and going slower. Ford found no codes, only on the third trip did someone find an EGR related code and thing to disconnect the cat and see what happened.

Where and how was the catalytic converter disconnected and how was the truck tested?

If not that, has your EGR system been checked?

 

Thanks for the tip, I have been wondering about that CAT more and more lately... the thing that is eating me about the CAT though is that it is only acting up after I've been running for several hours and working the truck hard: under load, hauling, plowing, etc... it doesn't appear to be affected when it's cold- then again maybe I have just been slowly getting used to it... and I would think that it would throw a code somewhere with regard to exhaust temps or back pressures or something! I will definitely check into the EGR as well.

Thanks, I'll keep you posted!

 

i'll agree with the cat being the problem as well.

just curious, why was the motor replaced with so little miles?

 

I concur, it sounds like the catalytic converter stopping up. The only thing is I've never heard of one clearing up and then stopping back up on a regular basis. The dealership should have a portable box to plug in and data log as you drive around for a couple of days. You might ask them.
Joe

p.s. I"M SURE NOT A TECK, heck I can't even spell it

 

With 135,000 miles on the original motor, it threw two plugs stripping the threads out of the head in one case. The plugs had roughly 50,000 miles on them and were due to be changed out anyway, these two just backed themselves out early... The local dealership wanted $1400 just to replace the head... and I couldn't find anyone locally that would heli-coil it, or at least noone that would back it up, So I pulled an engine from a salvage yard- it had an estimated 15,000 miles on it- and I swapped the whole works for just under $4,000. More money, but a whole lot less wear and tear on the rest of the motor.

 

That has been my sticking point on that theory as well... I guess I'm going to have to give the CAT a serious look.

The dealership had the truck for 2 days this last time and had the box plugged in both in the shop and on the road... or at least they say they did. In either case, no codes, no indications as to what the root of the problem is.

And again, I suppose it could be have been a gradual thing, this clogging up action going on in the CAT, something that has been slowly building up for the last few months, and maybe I've just gotten used to it not running properly- when its' cold... if that makes any sense

 

Pay real close attention to fuel press. to make sure regulater is'nt sticking I have seen the 5.4 do this after they have been running awhile.

 

Mine acted like that also, it would run fine, then after a few hours start losing power. The more you ran it the worse it would get. When you put your foot into it, the exhaust note would get strange....kind of like Fran Drescher's voice, if you can imagine that.

 

If I pull the CAT off (just for diagnosis), would the truck "rebound" immediately, or would the computer take half a tank of gas to get things back to working order?

 

The change was immediate and dramatic. You'll have no doubt if it is the cat causing the problem.

 

Yes on all acounts here except the part about Fran Drescher's voice... I'd have shot my truck and would be in therapy right now if that were the case...

But, when you put your foot into it, it does have a strange "deep gargling" tone that brings an image of something drowning to mind

 

Ok, the CAT comes off tomorrow... just to see. I'll let you know, thanks again for the advice.

 

Keep us posted.