I have recently picked up an older F350 2WD 7.3 DRW Lariat. the price was right higher miles but hey it is a 7.3, overall in very good shape.

So the issue at hand is the truck runs great most of the time and puttering around at city speeds you would never know there is any issue;

Get the truck out on the highway set the cruse at 70 to 72 and if you hit a rise in the road or other reason to slightly accelerate the truck chugs and bucks. For lack of a better description it goes chug chug chug, if you accelerate harder to downshift it goes away or if you back off the throttle it goes away. This happens with cruse on or off, a steady foot on the pedal will cause this as well.

I have also noticed that when you let off the throttle the sound the truck makes de-fueling is just very different and "off" sounding . Not sure how to describe it but it sounds funky ... clearly not right when compared to other 7.3 or my 6.0 truck.

What I have done, :

1. Had the truck scanned with an AE and a snap-on scanner both show no codes ran injector tests no contribution errors, not even in # 8.
2. Changed fuel filter
3. Changed Oil and Filters ( tried both full synthetic Rotella and Dino oil looking for a difference )
4. Cleaned out the fuel filter housing just in case.
5. Confirmed injector O-Rings are not leaking

This feels like a fuel issue, my next thought was start looking at fuel pressure under load at speed to see if there was a drop when this is happening ?

Is there a way to test fuel pumps in this truck ?

Maybe a clogged pick-up screen ?

Where do I start looking next ? I have reasonable mechanical skills but don't know this motor very well, this doesn't seem like a CPS issue, thoughts anyone ?

Thanks

tr0y

 

Check fuel pressure, under load, at full throttle. There are 1/8" NPT pipe plugs, one on each head you can use as test ports, or the post-filter port on the back of the fuel filter housing, near where the lines exit to the heads. That port is -4 ORB.

The symptoms sound more like worn injector poppet valve seats than a fuel pressure problem, but checking fuel pressure first is a good idea.

 

Bucking at foot pressure?

I have experience two things that cause what you describe. Do you have a chip? Did the previous owner replace, or in any way mess with the injectors?


IF it's a loose injector (or more), bucking on light acceleration is one of the very last "subtle" symptoms (there is a progression) of an injector losing torque. Soon after that, subtle rides the ejector seat - and obnoxious hops to the front. Do you get knocking or tinging up front? Is it far louder on one side than the other? Cackle is normal, but a practiced ear can sort out an injector knock.


If you are so inclined to pop the tops, please consult with the forum before just tightening a bunch of bolts - there's a procedure to this, and I paid a heavy price to learn it (15 times under there to get them to stay put).

 

Hi All -

Just got back to the truck after returning from winter in the southwest, the truck sat in a barn in Wisconsin all winter.

So it started fine after six months of sitting, had to plug it in as it was 40 out and the glow plugs are weak, this is getting fixed shortly.

If as Tugly said it is a loose injector what do I need to do to get it to stay put ? I have done injectors on the 6.0 motor is there a trick to the 7.3 ?

As for fuel pressure it according to my gauge got right to about 80 PSI on the rail and does not really waiver over a couple of pounds, it was never under 75 PSI.

Some other things I have tried with interesting results.

1. ICP sensor, unplugged it and the truck stops chugging, but throws a SES / CEL when it is unplugged. The truck is also down on power with the ICP unplugged.

You say, of course, it's the ICP, I replace the ICP with an OEM ICP and plug it back in the SES / CEL goes away but the truck still bucks with the brand new ICP.

2. Unplugged the Exhaust Back Pressure Sensor, unplugged slightly less buck / chug but still not gone.

Could this be Injector Stiction ?

Truck still throws no codes...

Thoughts anyone ?

T

 

Well with the ICP unplugged and it went away, then with a new one and its plugged back in its still there, I would go to the IPR. It would be nice to do some HPOP reading first.

 

A similar thing happened to me last summer. I was heading toColorado Springs and about Winslow the truck just started to slow down on alittle hill. I pulled over and drained the fuel bowl. Then drove it a littlefarther and finally changed out the fuel filter. It ran ok into Albuquerquethen started to act up. This went on the whole trip.<o></o>

Bottom line – drops your fuel tank and check the filters inthere – Mine were plugged up. It would run without a load but as soon as youpull a load it would buck and jerk then stall out. <o></o>

 

Hi All -

I am adding final resolutions to threads that were dormant due to me being away from the truck. This issue is 97% resolved, due to my turbo eating an airbox clip we replaced the wheel, we used a wicked wheel as a replacement, and a couple other parts and most of the chug and buck are gone. We have also seen a contribution error on cyl's 7 & 8 under heavy load, we are assuming it is stiction in those injectors, going to try the hotshot secret route with the next change of Rotella T-6 5-40 .

Happy Christmas

 

People have reported good results with Archoil also, I have tried it and had no ill effects. I use both the fuel and the oil additive.