1995 7.3 Power Loss/Flop during acceleration - Ford Powerstroke Diesel Forum
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Old 07-14-2008, 11:08 AM
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1995 7.3 Power Loss/Flop during acceleration

There are several things I know still need to be checked on this thing before I can truly rule anything out, but here's my situation and some history.

1995 F450 Dually - 7.3 PowerStroke (all stock configuration) - 5 spd. Manual - 220k miles

Truck starts and runs fine (has poor idle when cold due to 1 weak injector, but smooths out once warmed up). When first driving, you can feel the injector missing for about first 10 miles TOPS then it picks up and runs like a top.

After about 20-50 miles, if you get under heavy acceleration (between 1700 and 2500rpms) the truck bucks pretty bad -- easing off the accelerator and feathering it during acceleration cures this (with no load)... Of course, speeding up is much slower this way, but much easier on the neck... Now, say this is a highway trip - so 30 to 50 miles into the trip, running 55mph (RPMs at 2400) - 5th gear, no real load and not heavy on the pedal, Check Engine light will kick on and I can feel a definite change in the engine -- not a siginifigant power loss but there is some -- takes more pedal to hold the 2400 RPMs/55mph -- this thing is geared so low we only run it at 55mph or less...

OK, so when say there's a drop in speed (for an exit ramp or something) -- once RPMs drop under 2000 for a few seconds, Check Engine goes off and performance returns if not better, but jerking during heavy acceleration returns. If the Check Engine light is on, the jerking is completely gone, but it takes much more pedal to achieve acceleration and maintain.

Now, we mainly use this thing to pull trailers between 4000 and 10000 lbs, and this power loss means the truck generally has a hard time holding 55mph, but it does it. Acceleration sucks if Check Engine is on, but bucking activity stops (or atleast smooths out).

Repair History over last 6 months:
New valve cover gaskets including pigtails inside and outside
Glow Plugs checked and ok
Both Fuel tanks were flushed and cleaned/checked about 3 months ago
New Fuel Filter (several, obviously)
Oil Changed multiple times - we run Rotella-T
Top of Engine Fuel Pump changed less than 5k miles ago (behind fuel filter housing)

I know there are several real shop tests and scans that need to be run, but our scanner doesn't read this truck -- only our other 3. With the price of moving these days with a diesel fleet, we just don't have the money to throw into the shops to diagnose this thing and the three it's been into, they can't seem to figure out what's wrong with it (but I have very little faith in most shops anymore).

I greatly appreciate your help and if there's any questions or details I can answer, please let me know. IF you have specific tests and and idea of what they run financially, please point me in the right direction. This truck is a beast, and it runs like a raped ape when it wants to so we hate to just write it off and give up. Thanks again!
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