At 270k, we replaced the VP44 and injectors...figured it was about time. The truck has been doggish as of late (like the past couple years), and we figured it was injectors or tired VP44.

After replacing the VP and the sticks, the truck doesn't smoke at idle and the high RPM cruising is a lot better. But the midrange seems doggish...it will lose ground pulling a moderate hill (unloaded) in 5th, a hill it would cruise right up at one time.

What controls the fuel delivery? Am I overlooking a sensor some place that's limiting the fuel?? Filters have been replaced within the last 6k...but the VP44 and the injectors are the only maintenance (other than filters and oil) the engine has seen in 270k...

Am I missing something?

 

Try This

This is an article for cleaning the IAT sensor on the 1998-2002 24V diesel engine.
The IAT sensor measures the temperature of the intake nmanifold. The ECM uses this sensor reading to set injection timing and adjust the air-fuel ratio. If the fuel mileage and power output of you engine seem low, some owners have found improvement in EGT, fuel economy, and power after cleaning carbon from the IAT sensor in at the rear of the intage manifold. Engine with exhaust brakes are particularly prone to IAT sensor fouling because soot is blown back into the intake during valve overlap. Smokingdiesel.com has an information page about problems caused by the IAT sensor.

The only tool you need is a 3/8" ratchet with a 6" extension and 13/16" socket.

The IAT sensor is found on the driver's side of the engine, almost at the back of the intake manifold.


Unplug the electrical connector from the sensor. You will need to spread the connect tab away from the sensor body to unplug the sensor. After the connector has been removed, use a 13/16" deep well socket, 6" extension, and ratchet to unscrew the sensor from the manifold.


The sensor on the left had 20,000 miles on it, and it was covered with soot. After a shot of carburator cleaner, you can see the sensor element inside the cage. Screw the clean IAT sensor back into the manifold, torque it to 10 ft-lb, and reattach the connector.

 

After seeing how much carbon was on after 20k I figured mine was going to be 5 times as worse being that my truck has over 130k on it. Too my surprise it really wasn't bad at all. I'm sure it depends on what mods you have done & how you drive your truck. I got my truck used with 120k but don't think the previous owner did too much maintenance to the truck, but I could be wrong. It doesn't take long at all to clean the hardest part is getting it off the truck.
*Note - If you are double jointed the job will go a lot faster....
Temperature
Resistance
30°
40K
32°
30k to 36k ohms
76°
13K ohms
77°
9k to 11k ohms
81°
6.87K ohms
122°
3k to 4k ohms
130°
4K ohms
167°
600 to 675 ohms
212°
600 to 675 ohms
Replacement Sensor:

 

Since this one only has 270k on it, probably should just buy a new one. His mileage seems alright, still pushing around 18-20 highway.

Would the MAP sensor have anything to do with air/fuel (it should since its measuring boost and more boost should equal more fuel correct)??

I'm thinking of just replacing both of them, see if it makes a difference...

 

yes the MAP can prevent the Turbo from spooling

 

Next question, does the MAP simply screw out like the IAT...looks like it should??

I think we are chasing multiple issues...the smoking idle and main loss of power was the VP44 and the injectors with 270k on them (yes, an original VP44 with 270k on it)...and now there may be other parasitic losses of power (10 here and 10 there add up really quick)...

Thanks for the info, I know what I'll be doing the next time I'm home...

 

save ur money and start by cleaning the IAT. In almost every cases, that's all it takes to cure the problem. My 24v has 540k km's on it and I havent had to replace any of these parts yet. If you want some HP and torque gains, may I recommend the edge/juice!

 

The Map screws out as well

 

The APPS Adjustment got my truck back up to speed again when it was feelin sluggish. Here's a link to the thread with simple to follow directions. https://www.dieselbombers.com/5-9l-2...s-i-bored.html

 

Hmmm, seems straight forward enough...looks like I have another weekend wrenching on pop's truck!