2003 7.3, 116k, auto trans.

When sitting at idle I can here an intermittent humming noise. When it happens you can feel the truck vibrate slightly. I had my 4" MBRP exhaust installed today and the surge/humming is even more evident because it changes the tone of the exhaust ever so slightly.

I have an auxiliary idle controller so I am able to monitor the exact RPM of the engine and it does not change with the humming noise. It'll it happens every 3-5 seconds when idling warm. Does not happen, or at least not noticeable when the engine is cold.

I've had two other 7.3s, one a 2003 an the other a 1999 and neither have done this. AC/heater off or on makes no change.

Could it possibly be my vacuum pump? I don't know. If so, where is it located?

 

i'm just throwing this out but , you might try pulling your belt off and spin/check/inspect all the pulley's but i guess that would change the rpm's

 

mine did that. Changed the IPR and it solved my issue plus hot restart was much better. I think the electrical part of my sensor was going.

 

I do have an aeroforce gauge which can monitor IPR. Anyone know what values I should be looking for? Should they be constant?

 

Check out Tugley's thread titled "AE class in session" He mentions it a few times. The icp should be around 600 with the engine warm, and IPR I THINK AROUND 17%, BUT DONT QUOTE ME ON THAT. I'd have to check to make sure, but they do fluctuate a little.

https://www.ford-trucks.com/forums/1...n-session.html

 

When I had he gray CPS installed on my truck, it did exactly what u described. Just a little miss at idle. I swapped the black one back in and it went away.

 

I also had this problem when I ran the grey CPS.

 

My CPS was changed out a couple months ago by the dealership under recall... How do I get a black CPS?

I just bought the truck in feb and don't remember if I noticed this before or not. But it is annoying as hell that's for sure!

Aeroforce gauge says my injector control pressure is between 450 to 600 at idle... usually around 550.

 

you can get a new CPS from Riffraff or go to the international dealer, I think Guzzle sells them to on Diesel O'rings.

Icp should be good at that pressure, warm at idle.

 

The old "black" CPS as it's meant cannot be purchased anymore. They've been replaced by revised editions.

There are people who have personal stockpiles, but I haven't seen a true "black" CPS sold since Clay was able to locate a stash from somewhere, a couple years ago.

Stewart

 

You should see an ICP of about 2200 PSI while cranking, 700 PSI while idling dead-cold, and about 500-ish when warmed up at idle. Engine Oil Temperature tells the PCM when it needs to alter the ICP setting to get better atomization when cold or cranking.

IPR is typically about 11% when ICP is 500 PSI, and about 14% when ICP is 700 PSI (at idle). This is for a stock truck with good working HPOP and sensors. Different sticks, bad sensors, high idle, and/or an HPOP mod throws these numbers to the wind.

One more caveat: I see these numbers on synthetic oil... I can't be sure of dead dinos.

 

I'm getting this to only after I change the HPOP to new T500 and resealed the injectors

 

Do you have any kind of scan tool to watch and record live data? How old is your oil, These trucks like their oil fresh.

Is it just surging a little or really bad? My ICP went out after installing my T500, like minutes after, and have heard of others too. I think maybe mine was going bad then with the extra pressure from the new HPOP finished it off.

Try unpluging the ICP and see if it makes a differance.

 

Oils new, surge is not real bad but I can't live with it. The ICP which I take is the In Injector Pressure Regulator found screwed into the HPOP. It's supposed to be new as have paid $ 128 for a new one that the shop that did most of my work. So many new parts don't know. First bit of work $6500.00. I really don't like some mechanics.

 

Icp is injection control pressure. It's a sensor that tells the pcm what the hpop is at. It is in the drivers side head next to the fuel bowl