7.3 Intermittent Power Loss - Ford Powerstroke Diesel Forum
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Old 07-10-2012, 11:27 AM
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7.3 Intermittent Power Loss

I have a late model 99 7.3 diesel and have noticed some problems with intermittent power fluctuation while driving. Sometimes the motor sounds muffled, but the noise will get high pitched and it has more power intermittently. This might happen 2 or 3 times up a large hill, and sometimes it doesn't happen at all. The pickup starts and idles well. The noise difference sounds similar to comparing the stock to the 80e tune. The 80e tune sounds higher pitched. I noticed the problem on 80 tow while pulling load. I've logged some operating conditions with my OTC Genysis and would like some opinions on this. Here's what i found:

In park idling @ 675 RPM with the 80 econ tune and oil temp of 194 degrees the icp was 655 psi

In park holding the RPM at 1360 rpm
Stock tune: ICP = 722 psi at 14% duty cycle
80 Econ: ICP = 921 psi at 14% duty cycle
60 tow: icp = 880 psi at 15% duty cycle


Driving up a hill at 1600 rpm on the 80 econ tune, ICP = 1400psi at 21% duty cycle

Full throttle run from 60 to 90 mph

Stock mode the max duty cycle I saw was 57%, ICP stabilized at 2400 psi The P1211 code was set

80 econ mode The duty cycle peaked at 80% at the end of the test, ICP held 2163 psi the P1211 and P0238 codes were set. Once I stopped I hit the gas and nothing happened, a second later the power kicked in hard and it ran fine all the way home.

I have replaced the fuel filter and pulled the wire off of the ICP and there was no oil in the connector. Any information would be greatly appreciated.
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Old 01-10-2013, 09:57 AM
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I see you have no replies but did you figure out your issue? Ive got the same issue with my late 99 thanks
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Old 01-10-2013, 10:01 AM
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My problem ended up being the injection control pressure regulator. I bought a seal kit, took it apart, and cleaned it. I haven't had a problem since.
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Old 01-21-2013, 08:00 AM
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I have a 2002 7.3 that shuts off from time to time. It maintains good performance without power fluctuation but when I pull up to a stop light, it will die. It becomes very difficult to start as though it's lost prime.
I may move the water separator lever behind the fuel filter and it'll restart. Other times, it must sit for fifteen to twenty minutes. Once it does start, it has good power and sounds fine.
It first showed signs when it was low on fuel but now I keep the tank full and it's still doing it.
If anyone can help me, I would appreciate your advice!
I took the Ford F250 Excursion to a local parts store who placed in on a computer. There was no found problems with the vehicle.... however, it shot off twice leaving their parking lot
Thanks so much!
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Old 01-21-2013, 08:04 AM
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It sounds like it's loosing fuel pressure. I'd install a fuel pressure gauge at your filter housing and see if it drops off when this happens. Normally a positive displacement pump will not intermittently drop pressure, but that's what it sounds like. If you put it under a hard load does it run alright, or does it seem to be starving for fuel?

Another thing that could cause this is losing your injection control pressure. You can watch your ICP with a scan tool in the vehicle's datastream.
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Old 01-21-2013, 08:23 AM
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Question It has plenty of power... when it runs!

It does not lack for power. I tow a huge buggy with this Ford Excursion and it goes down the road like it should!
Only when I come to a stop and take my foot off the fuel, it may shut off, or when it idles it will shut off at times , with no warning. This is an intermittent problem and does not happen all the time.
When it restarts it does not miss, it runs strong, as though nothing was wrong what so ever!
Over the Christmas holiday I was caught in a huge traffic jam only to have it shut off! I tried my best to restart that engine with no luck. Someone was kind enough to tow me out of the intersection to a location along side the road out of traffic. Low and behold.... I had no sooner pulled to the curb when I hit the key once and it started up and came home without any other incident.
I've used it several times since but only around areas without traffic and on side roads where no one will be upset should I break down.
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Old 02-04-2013, 05:36 PM
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i have a 96 f250 with a 7.3 and it recently jerked a couple of times at 30 to 35 mph doesnseem to loose power and doesnt do it very often just once in awhile i changed the fuel filter and put howes add in it and it didnt do it for 2 months then di it again twice
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