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Irratic Idle/Lack of Power-2001 Diesel

Replaced: Air/Oil Filter, Fuel Pump, Upper Engine Injector Oil, Cam Shaft Positioning Sensor, Sensor ICP, NO CHANGES-Need to get out of town for Funeral and need guidance.

Any ideas? Vehicle has a Lack of Power and Irratic Power…Can get it to HWY speed but it still has lack of power.

This cant be good…no one is responding…

How many miles? Is it possible you have a “tired” engine? Compression is critical with a diesel and if you aren’t getting proper compression on all cylinders then replacing all the parts in the world won’t solve your problem.

Perhaps you need to talk to truck mechanics that work on diesels all the time for some ideas on what’s going on.

Truck has 360000 miles is well cared for and began running on Bio Diesel 2 years ago and has done very well. I have been impressed. This happened at once not gradual. If it were a tired engine I would think that it would be gradual. Is there anything you can suggest before I rip the motor apart to check the compression?..We are on limited time for getting out of town

Check all the electrical connections you can assess that involve the fuel delivery and management system. Perhaps a contact is not being made, or a vacuum hose has a leak. Sometimes the plastic connectors on vacuum hoses crack and are not easy to spot.

You may need to rent a car for your trip, and deal with this when you don’t have as much time pressure.

Had thought of the vacuum but the 7.3 doesn’t use or produce vacuum. It has a seporate vacuum pump. And I have checked every connection iI could find

Explain Bio-Diesel.

If bio-diesel isn’t refined correctly to remove the amino acids, these acids will attack the seals in the injector pump and injectors. And this will cause a diesel engine to run rough and lack power.

You may also want to read what Navistar recommends about using Bio-Diesel in their engines.


I’m thinking you have a fuel hose collapsed on the inside blocking fuel. Especially concerned based on your hint that you have started using biodiesel in a vehicle that was not designed with biodiesel in mind.

A Diesel engine will run on a lot of different stuff, but the designers may not have provided chemical compatibility for anything other than Diesel #2. Same sort of issue as with ethanol in gasoline.

Older diesels with black rubber fuel lines start breaking down with biodiesel. Newer diesels with teflon lines dont break down with boidiesel.

Just finished swapping out the PCM for a knowned good one out of a friends truck with no change

380000 miles should be half life. I bought the truck with 350000 two years ago.