Hello,
I recently bought a 2001 class C motorhome on an E450 chassis, with the V10 engine. In general, it seems to run well, starts right up, idles smoothly, fuel economy on the 14K lb M/H is close to 10mpg if I'm really careful. However - the last two times we took it out, I noticed that when, for example, climbing a hill, the ECU would downshift as expected, but when it subsequently upshifted, the RV shuddered/surged very noticeably. I'm familiar with what misfire sounds like, and the engine sound was very steady. Also, no codes have been set. I also notice a bit of the same kind of shudder/surge at higher RPM when accelerating onto a freeway, but it is not nearly as bad. It is the lower RPM high throttle situation that seems to cause the most problem. I live at 4700 feet, this past week we went from here to close to sea level and back, and altitude did not seem to make any difference. I also added two cans of Seafoam to the fuel tank before wee lefty, in the hopes that I might have had a sticky/dirty injector, but did not notice any real difference. I recently changed the air filter, and replaced the 165 degree thermostat the PO had installed with a 190 degree part. No difference seen after that.
I had thought that possibly the lockup clutch in the converter might be cycling rapidly? Does that make any sense? At this point, I'm kind of stumped.

 

I have something similar, see post from last year https://www.ford-trucks.com/forums/1...nder-load.html

Last thing I did was run it with the engine cover off ( man that engine throws some heat ! ) , didn't see any shaking of the engine but could feel a slight shudder in the MH near the top of some hills ...no codes set.

It got cold here pretty early last year so I had to concentrate on getting it ready for winter, still cold but at least I have the RV cover off . I intend to replace the COP boots, clean out the spark plugs wells , torque the plugs and see if that helps. Next will be either change the plugs or COPS or both

 

Two things. Clean the MAF sensor. Also, I'm not sure if it was a TSB for the Class C or the Class A, but check the air filter and see if it's wet. Was it raining at the time?

After that, I suspect a loss of fuel pressure. You have a Schrader (tire) valve on the fuel rail - connect a fuel pressure gauge to it, and take it for a drive. At idle, it should be around 28-30 PSI, under load it should go up to 38-40 PSI. If under load, it jumps to 38-40, but then drops off, you have a fuel supply problem.

 

Hmmm... I have a can of MAF cleaner, I'll try that. Weather was fine, no rain. As I mentioned, no codes/check engine light, so I'm not sure about coils - in the past, when coils have been bad on other vehicles, there is a very definite sound/feel that this situation doesn't have, but if nothing else comes up, I'll give the coils a try.
I think the best way to describe what it feels like is that it's as if the throttle was being wiggled rapidly, or as I mentioned earlier, the lockup clutch was engaging/disengaging.
The fuel pressure test sounds good - I'll have to get a gauge.
Thanks for the tips, I'll keep looking!

 

Report back what you find, and we can continue working the problem

 

What is the OEM thermostat tempature on this vehicle?

PCM estimates tempature rise between maf and intake valves and using a tstat that increases engine temp or decreases it substantially may confuse things.

Try getting oem temp tstat and disconnect battery for 30 min. This may reset fuel trims that could be off due to tstat change.