2002 F550 with 7.3 runs rough when cold - Diesel Forum - TheDieselStop.com
'99 & up 7.3L Power Stroke Engine and Drivetrain Discussion of the '99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.

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post #1 of 6 (permalink) Old 08-07-2011, 01:51 PM Thread Starter
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2002 F550 with 7.3 runs rough when cold

I have a 2002 F550 with 7.3 powerstroke. A little slow to start. Runs rough when it starts and has no power until the motor warms up. No codes in computer. Truck has 135K miles.
Does anyone have any ideas?
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post #2 of 6 (permalink) Old 08-07-2011, 02:28 PM
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Do you have scanning software that can monitor engine parameters? I guess the first thing I would do is make sure the fluids and filters are good and up to date, then check the fuel pressure. You should have 50-60psi running. Are you getting any white smoke while it's cold?

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post #3 of 6 (permalink) Old 08-07-2011, 02:43 PM
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i agree with tinman if have access to that (scan tool) then check out.

if not same thing happened to my buddies excursion w/ 7.3, when first started was hard to start and missed like crazy when warmed up ran like normal. ended up being the passenger side valve cover gasket had came unplugged barely enough not to let that side do its thing. like i said looked like was plugged in all the way but wasn't so maybe thats it?

check fluids though, smell oil see if diluted with fuel.

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post #4 of 6 (permalink) Old 08-07-2011, 03:17 PM Thread Starter
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Yes I have SnapOn software. I have fuel pressure. I have a new fuel filter. No white smoke.
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post #5 of 6 (permalink) Old 08-07-2011, 03:33 PM
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Have you run a scan to see if there are any codes? That's the first step.

Also check the oil age, condition, etc. Used-up oil can cause problems with the injectors. Possibly one or more are gunked up on the oil side and won't operate correctly until the oil warms up and thins out a bit. Run an injector buzz test when cold, listening for differences in the sound of each injector (weaker than the rest), and then run one again after the engine is warmed up and running well. The weak sounding injectors will be the suspects. The buzz test activates all 8 injectors, then each one individually in numerical sequence (not firing order).

If you narrow it down, pull that valve cover, and pull the solenoids off the suspect injector and measure the clearance under the plate that the solenoid pulls up with a feeler gauge. IIRC, anything under 0.001 means the injector is worn out. While you're in there, check the under valve cover harnesses as mentioned. But at 135k miles, I'd guess your injectors should be fine if maintenance (oil changes) has been kept up and good quality fuel has been used.

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post #6 of 6 (permalink) Old 08-07-2011, 07:42 PM Thread Starter
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just ran an injector buzz test before motor was warmed up and found #2,#4,AND#8 were weak. Will try that. Thank you
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