My 2005 F350 6.0 basically runs great, except; when going down the road the truck accelerates fine until about mid range and then sort of stumbles like a miss. Give it a little throttle and it goes away. Doesn't happen out on the highway at high speeds. Seems to only happen on the slower roads and just before the tork converter locks up. I had the truck scanned and they said #3 injector looked a little week. I replace that with absolutly no change. Again the truck runs smooth on the highway and gets me 19-20 mpg hand calculated. Also, the injector harness was just replaced and the FICM tests at 48v starting and running. Any ideas?

tks
David

 

Possible EGR valve malfunction. Take it out and douche it good.

 

Is it a stumble/miss or a shudder? My truck does the same at about 45-55 MPH and sometimes in the mid range around town. I have a bad carrier bearing. Maybe that's your issue.

 

I had a bit of a stumble in mine while accelerating and it ended up being the IPR valve.

It took a while to figure out what it was, EGR was deleted, and I thought it might be injectors, but I posted on here:
https://www.ford-trucks.com/forums/1...ors-maybe.html
and Bismic suggested it might be the IPR valve.

I picked an IPR valve up for $173 from my local international dealership and that fixed it. My international guys help me out alot and are really good guys. they will cross reference anything for me.

 

The stumble and then run great is now a definate miss. Its not throwing any codes so I had it scanned again. They now say cyl 1 & 7 are low but think the main problem is the FICM. There readings were 47 to 48volts but he said they were moving back and forth erratically and probably worse under load. Does this all sound right? I thought 47-48volt was an ok value but I don't know about the bouncing back and forth.

FICM, IPR, Injectors, which one first??

 

Is it only on acceleration or is it constant?, it could be fuel pressure too.

 

Truck starts and idles ok, start going down the road and is ok up to about 15mph then start to miss. The mis is now pretty constant but does sometime fade away. Its not throwing any codes or blowing any smoke.

 

When I got out on the highway and got speed up to 60-65mph truck ram fine, there may have been a slight miss but overall smooth. Then get off highway and drop to 30mph and the rumble sstumble is back. The miss goes away at idle. Could the FICM be dropping voltage at mid range?

 

try unplugging the egr valve. mine had the same symptoms and i unplugged it and it went away. havent decided to get new valve or delete it.

 

Just because FICM voltage is good doesn't mean the FICM is good. If you have low circuit codes (1&7 are on the same connector) your FICM is probably toast.