intermittent MISS???? - Ford Powerstroke Diesel Forum
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post #1 of 7 Old 12-22-2009, 09:19 AM Thread Starter
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intermittent MISS????

Guys this is going to drive me nuts if I don't figure it out. I just bought a 04 6.0 excursion and it has this odd miss/surge. The truck starts great hot, cold, whatever. Temp has nothing to do with it. It idles smooth as can be, no miss what-so-ever. However, it has this stumble that starts to develope as you pass say 1/2-3/4 throttle as well as a very slight miss at hwy cruising speeds 65-70 mph anything over 2000 rpms. It doesn't do this all the time, but most of the time. If you go past just holding steady speed on the hwy it smooths right out. However, go past 1/2-3/4 throttle and it has a miss again. I have had it scanned and there are no codes. Had the diesel mechanic run all the tests on it with his mac navigator or whatever and it passes all the tests for the injectors. At idle the truck is showing 900-1000 psi for the HPOP and at 2500-3000 rpms in nuetral it goes to 1500-1700. It does seem to have a minor oil leak coming from the ICP. Any suggestions on how to fix or what to check would be much appreciated. Thanks in advance, Drew
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post #2 of 7 Old 12-22-2009, 11:21 AM
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If its not a loose wire at the FICM I would suspect the accelerator pedal potentiometer.
A dead spot in its sweep maybe. Since it seems to happen at set speeds as best I can make out You can test this with a good DVOM by watching the voltage change as you slowly and as smoothly as possible go from no accell to full accel. You should get a steady even increase in voltage.
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post #3 of 7 Old 12-22-2009, 01:16 PM
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I agree with dannyboy...It sounds like its a throttle position thing. You are getting it in the same position of the throttle pedal, not really a certain speed or RPM. I run into the same symptoms on the electronically controlled big rigs. Go after that first and let everybody know what you find. If it is that, you probably wouldn't be getting codes, like you said you weren't. I would think that anything with the FICM, even intermittent, would throw a code at ya. Could be wrong...wouldn't be the first time, won't be the last!

Good luck, keep us posted!
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post #4 of 7 Old 12-22-2009, 07:10 PM Thread Starter
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Thanks for the advice guys. I will check that indeed. Could this also be the cause of the miss at wide open throttle? Thanks again, Drew
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post #5 of 7 Old 12-24-2009, 10:56 AM Thread Starter
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Well guys thanks again for all of your help. It sort of helped me solve the problem before I got too deep into checking. The other morning I went out to start the truck and it wouldn't turn over fast enough to start. I thought well the cold must be getting to my batteries. Took two mac tools jump boxes and started right up. Drove it on and off the rest of the day. Probably turned it off and started it 10 times with no issues. Went out to start it the next morning and same thing, wouldn't crank. Boosted it off again and decided to test the alternator. Turns out at idle all it was making was 12.1 volts and a max of 12.7 at 2500 rpms warm of course. So I got sorta miffed that I was gonna have to throw an alternator on it with this miss on top of things. Installed a new alternator this morning and it runs like a top!!!! No miss at WOT, no miss at cruising speeds, no miss period. The moral to this story check your voltage if you have a miss. My alternator was charging just enough to keep the idiot light out, but not enough to run right. Remember, I have had this miss for almost 2 weeks now. Thanks again and I hope this helps someone else out. Drew
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post #6 of 7 Old 12-25-2009, 03:38 AM
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Thats awesome, never seen that happen before. And also for anyone who may think they have a HP oil leak, watch the IPR duty cycle. If there is a leak, the duty cycle will slowly increase to compensate for the leak.

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Specializing in: 6.0, 6.4, 6.7, and 7.3 Powerstroke Diesel

Currently Employed as a Diesel Technician for the
Walt Disney World Resort in Orlando, FL.
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post #7 of 7 Old 12-25-2009, 03:45 AM
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Glad ya got it going. I have seen low voltages cause injection problems but usually it affects all cylinders not just one. Good info to know thanks.
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