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Ask Juan Crespo Your Own Question
Juan Crespo
Juan Crespo, Tech Trainer
Category: Ford
Satisfied Customers: 1524
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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I am working on a ford 2004 f350 with 6.0 diesel. The

Customer Question

I am working on a ford 2004 f350 with 6.0 diesel. The problem i am having is when engine reaches operating temperature is misses from 1800 rpm to WOT . There is white smoke coming out of exhaust and the engine hunts when you get to the rpm of 1800 . At idle the engine runs good. When the engine is cold it runs good. When engine misses the boost pressure is only about 8 psi. I cleaned fuel tank, replaced fuel pump, filters, replaced fuel regulator valve, replaced icp sensor. I replaced map sensor , hose , and cleaned out nipple on intake where hose attaches. I cleaned egr valve. I have 2 codes that keep coming back. po407 po488 Can you help?
Submitted: 1 year ago.
Category: Ford
Expert:  roy replied 1 year ago.

good afternoon my name is ***** ***** I will assist

the white smoke is an indicator of coolant in the combustion chambers. it will also cause the missfire

the codes are related to the egr failure. when you cleaned the egr, was the coolant present???

Roy

Customer: replied 1 year ago.

no coolant in egr port

Expert:  roy replied 1 year ago.

both codes indicate that the egr is the issue. sometimes you do not see the coolant but it may be there. the white smoke is a confirmation.

Roy

Customer: replied 1 year ago.

I run engine until I got it to miss. I removed egr valve and pressured cooling system for 4 hours and have no sign of coolant in the intake. the smoke has a gray tent to it

Expert:  Juan Crespo replied 1 year ago.

Hi there. Different expert here.

The codes you mention point to a problem with the return signal turn circuit from the EGR throttle position sensor to the PCM; P0407 indicates signal voltage too low, while P0488 indicates signal voltage out of range - basically, what these codes are telling us is that the return signal voltage is actually lower than what the parameter allows.

For the cause of these codes, we should look first at the condition of the throttle body. Carbon and/or oil deposits can cause the throttle plate actuator to fail causing driveability problems. So first step should be to make sure the throttle body plate is clean and free to be opened and closed by the actuator.

If the throttle plate was found to be clean and operating correctly, then our second step would be to test the position sensor signal voltages - best way to do this would be with a VCM loaded with IDS software, but we could also use either a good DMM or a scope. Have any of those available?

Customer: replied 1 year ago.

trottle plate is clean besides a little oil film. How can I tell if trottle plate is operating correctly?

Expert:  Juan Crespo replied 1 year ago.

We can assume is operating correctly if the plate is clean and there are no signs of binding on the throttle bore.

Customer: replied 1 year ago.

I have a snap on modis. Is this suitable for the test? If so , can you explain the procedure? i also have mulimeter

Expert:  Juan Crespo replied 1 year ago.

I'm not familiar with the snap on modis, but we can perform the tests with the multimeter. Just give me a few minutes to dig up the wiring diag. Hang in there...

Expert:  Juan Crespo replied 1 year ago.

Hey, just curious, can that modis read this kind of PID's? If yes, it would make both our jobs a lot easier....

Customer: replied 1 year ago.

which pids you need. I can check the data screen

Expert:  Juan Crespo replied 1 year ago.

Well, for PIDs, we'd like to see EGRTP position return signal; for actuator tests, I'd like to be able to command the EGRTP actuator OPEN and CLOSED. Can it do that?

Expert:  Juan Crespo replied 1 year ago.

I don't mean to blow your mind or anything (heck, mine is already blown, we sure don't need another casualty ;-), but I wanted you to have an idea of what we're trying to diagnose, so I've attached a document describing the system and what causes it to set code P0488.

Expert:  Juan Crespo replied 1 year ago.

Did I loose you? Anything on that PID or actuator test? Can your multimeter ot the modis read frequency (Hz)? If not, then all we can basically do is check for VREF voltage and return signal at the EGRTP position sensor:

VREF (Brown/White wire) should be between 4.5 and 4.9 volts

Return signal (Light Blue/Orange wire) should be less than 1 volt with the plate closed and increase to more than 4.4 volts with the plate wide open.

Please let me know if you'd like to continue this diagnosis, if not, please tell me so.

Best regards.