7.3 stumbling - Ford Powerstroke Diesel Forum
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post #1 of 4 Old 01-08-2012, 12:21 PM Thread Starter
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7.3 stumbling

Great forum btw. Im done some reading and research and i just wanted some imput as to weather i should buy this van or not. Its an 03 e350 with the 7.3. Its in pretty good shape and i will be using for my daily driver and towing. It starts up and idles just fine, but when u get near the gas under any kind of load it starts stumbling/missing and wont get out of its own way. It pours smoke when its doing this as well. I drove it and it got worse until it finally stalled. But would always restart. Sometimes sounding like it was only running on 6-7 cyl. No cel or codes. I replaced the fuel filter and cleaned the bowl. Ran better for a few sec then back to the way it was. Any insite would be greatly appeiceated.
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post #2 of 4 Old 01-08-2012, 01:03 PM
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First, Do NOT buy it until you figure-out what the problem is, it could be a $100 problem or a $5,000 problem Invest some money if you have to, but Find Out First!

Next, what are you using to scan it? Our trucks are not specifically OBD-II and, regular OBD-II scanners won't properly pull codes, so, without the right equipment you don't even know if there are codes present.

If it were me, I'd take it somewhere for an evaluation. Find a Really good diesel shop who knows these engines (do your research) or into a GOOD Dealership. Where are you located? Maybe someone here can direct you... Even though the dealer will cost You the most, you'll also get the highest repair estimate to bring to your seller
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post #3 of 4 Old 01-08-2012, 01:16 PM Thread Starter
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The van has 94k on the clock and i was using a snap on modis tto scan the van. Im a tech, just no familiar with diesel's. But im open to learn!
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post #4 of 4 Old 01-08-2012, 01:46 PM
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OK good, sounds like you've got the right tools & skills

I don't use a Snap-On, so I can't help you with the specifics, but here's what you want to see ->

You need to check ICP and the IPR duty cycle. When cranking on the truck you should watch your ICP quickly jump from 0 psi to 15, 100, 250, 400+ psi and once it goes past 400 psi it should start. Meanwhile your IPR should be ramping up in a similarly quick fashion while cranking. You should see 9 - 14 volts with the key on depending upon the condition of the IPR. It should ramp up from 14 to 20, 25, 30, 32 etc... and level out around <35 psi in order to start.

If it ramps up to 65, 75, 85 etc, there is another issue at hand. Watch your ICP/IPR while idling. ICP should stay around 500-700 psi and IPR should stay around 9-14v.

Finally if all that passes, we need to know what your fuel pressure is when you turn your key on, while you're cranking and once it is started. The truck may start and sputter if you're getting 20 psi or less... but most likely this isn't your problem. I have seen trucks with dead pumps get started and then the injectors siphoned enough fuel to stay running even though the gauge showed 0 psi of fuel pressure.


Here's some specifics from the AutoEnginuity I use ->

If you hook up the scantool, and monitor ICP (psi) while cranking...you'll see IPR% (duty cycle) climb & climb 15% key on..20, 30, 40, 55%, higher..the increase in

IPR% means that the PCM is requesting ICP pressure to increase... so ALSO watch ICP (psi) and if it comes up to only 180-250psi or so and stays there...then it's the

IPR hung open (bypassing oil back to the oil pan through the front cover) such that only minimal psi can be made.

If the ICP is VERY low...like under 60psi...then it could be injector (poppets) pissing oil (under the VC's)..which is typical for injector with more than 180-200k

miles. If ICP climbs above 550-600..then it will probably climb much higher (15-1800+) and it is most likely going to be an electrical issue.

If the scantool will not connect then its a PCM or chip issue (remove the chip if you have one & haven't removed it yet) if the scantool connects AND you have

>600ICP then look at the datastream for a RPM reading. If the scantool picks up an RPM signal and it seems accurate....then the CPS is good.

If no RPM on the scantool, replace CPS. If you have RPM (on scantool, not just on dash)...AND have ICP >600, then run an (key on, eng off) injector "buzz test"...

the buzz test is nothing more than a continuity test from the PCM, through the IDM, and to & from each injector solenoid. LISTEN to each inj buzz....do they all

sound the same? nice & crisp? If the test passes (and you audibly heard them all)...then wiring is good, IDM is good, HPOP is good...CPS is good...then it could be a

fuel issue. gasoline, water, etc... I wouldn't mention it if I haven't seen it myself numerous times... any chance this no start began with 10-20miles after a


If you have a scan tool ICP should be 500 PSI 25 PSI and fuel pulse width should be 1 to 6 milliseconds.

The above requirements assume the following:
Correct oil level, oil type and pressure
Correct type of fuel
Correct fuel pressure (53 PSI per Ford spec)
Sufficient air supply (clean air filter & unobstructed intake)
Proper oil level in HPOP reservoir (1 to inch from top)
Proper glow plug relay and glow plug operation (in cold weather)
Proper injection timing (PCM controlled)


Also, you could try disconnecting the plug on the ICP sensor to tell the IPR to go full open. Did you check the plug and sheet metal nut going to the IPR? Try "rapping"
on the IPR with a screwdriver handle, sometimes if stuck, you can "free it up". Also, check the valve cover harnesses, and make sure they are plugged in. The ICP sensor can be fluky and a good indication of that is oil leaking through it and into the connector.

I always think of fuel delivery too in a situation where you have No Codes so drive it and monitor the fuel pressure if you can.
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