I've recently picked up a 2000 Excursion/7.3L from my old man. It has about 190K miles on it. He put about 80K since 2004 and except for oil changes, filters, hub, and brake work, has not done anything else. To my knowledge the Truck as 8 original injectors and original turbo.

The truck generally runs well, but it was rarely used so I expected that some things would pop up as I started really driving it. I've only put about 1000 miles on it since I picked it up. Recently, I've noticed an erratic idle when fully warmed up. Howover, I have not noticed a power loss under acceleration.

I connected my AE scanner. It reveals code P0284 for cylinder 8. I ran a contribution balance test and it also shows the same problem in cylinder 8. My experience has been with the 6.0, so I read a lot of what is on the web about the 7.3 in this situation. While the P0284 code was there, and the uneven idle, I looked at the rotational velocities. All cylinders show 0.0 except cylinder #8 which ranged from 3 to about 5.5. This seems to indicate a bad injector to me. However, I've read that a bad CPS can cause a P0284 fault as well. Question, can the bad CPS also cause rotational velocity to be 3 to 5.5 out as well? Meaning should I swap out the CPS because it is easy and cheap or is this a slam dunk bad injector?

thanks for the help.

 

The #8 injector suffers from being at the end of the fuel rail and firing right after #6, which precedes it on the fuel rail, a double whammy which can affect fuel delivery. There's a Long Lead injector (LL) that's meant to resolve this problem. I don't know if the LL injector is OE for these engines, or whether it was originally a replacement for those who complained and then became OE at a later date. But anyway, if this is the cause, then a new CPS won't resolve it, but an LL injector (if you don't have one already) might. Another solution is to install a regulated return fuel crossover kit, which is a minor modification which improves fuel flow through the fuel rails and should allow a regular injector to work fine in the #8 position.

If you already have an LL injector there, then you might have an actual injector problem. Others with more info will certainly chime in.

 

Thanks for the inputs. I don't know what injector is in there now, but if I do pull it out I will look for a LL injector. Anybody else have any ideas?

thanks.

 

3-5% out on PERDELS for #8 is pretty much normal. #3 will also be off a bit sometimes. See chart I purloined from Woodenthings.

First thing I'd do is pull the harness off the ICP and see if it's leaking oil. Also make sure the tin nut on the IPR is on, and snug. Feeling it's related more to ICP issues when warm than an injector. If you're handy with AE a log during symptoms would be fabulous. Or at least monitor ICP.

 

If you do pull your valve covers, the regular injectors are AD, and the LL if installed is an AE. Pretty sure that the original injectors are all Ad's.

But as Aawl implied, it's easier to check out the external things before you start diving under the covers. Another question, does it get better with more than a quarter tank of fuel?

 

When was the last time the oil was changed. The #8 readings are well withing the newer CPS readings on both contribution and rotational velocity.

 

Great food for thought. Thank you everyone.

First, I haven't looked to see which CPS is installed. I will try to do that today.

I am at 1/4 tank now, but don't recall if the problem has changed with fuel level. I will try to refuel it and see if that changes things.

I had glanced at ICP and IPR and thought they looked ok (given my 6.0 experience), but I will try to get some readings on first crank of the day, warm idle, and WOT. I know I saw a warm WOT hit 2800psi, but I forget the duty cycle on the IPR, but didn't think it was maxed out.

One more thought to add. Does it change your feeling that #8 may be normal at 3 to 5% if it was reading zero until the engine warmed up?

 

I would research the Hutch mod before looking at an injector. You can swap the CPS to "jiggle the handle on the toilet", and it might help the reading - but air in fuel is the Superduty curse. It's at it's worst at 1/4 tank or less because at that point, the elevation of the fuel dips below the fuel pump. This means the fuel is no longer pushing down to the pump, but the pump is now sucking on the fuel like a straw - and the fuel pickup system doesn't seal well against a vacuum.