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Bouncing Rpms

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Old Jul 16, 2013 | 09:11 PM
  #1  
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Bouncing Rpms

http://static.photobucket.com/player.swf?file=http://vid146.photobucket.com/albums/r274/Orpackrat/video-2013-07-15_05-55-20_zps0c74e022.mp4

'85 F350 6.9 C6 Auto, got to swap in a 7.3 IDIT by Sunday from a '90 F250 with 5-speed. Have planned a rebuild on the 6.9 after the swap.

Anyways, truck started bouncing the RPM's as seen if you copy and paste the above. Had to drive to work, ran just fine at higher rpm but at idle and a bit above idle, it bounces.

Got to drive home 65 miles where I hope to keep it parked if I dont have to go anywhere till I swap engines.

My question is, should I be concerened for my drive home and what is causing it so I can fix it in the planned rebuild.
 
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Old Jul 16, 2013 | 09:41 PM
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Sound likes its getting starved of fuel, I'd change the fuel filter and see if it improves, I'm guessing also its lacking power when you rev it up.
 
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Old Jul 16, 2013 | 10:23 PM
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I changed the fuel filter before I left for work and while it helped, it was only slightly.
 
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Old Jul 16, 2013 | 10:36 PM
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have you check the other fuel filter...the one in the water separator? sometimes that'll get blocked up. under driver's side frame or in driver's firewall corner next to booster... they have a tendency to leak and suck air in
 
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Old Jul 16, 2013 | 10:49 PM
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Water seperator removed by PO, has a filter assembly but was bypassed when it clogged badly from the PO running Biodiesel and never changing it.
 
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Old Jul 16, 2013 | 10:56 PM
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Bio-diesel, or WVO? Even decent Bio wont affect these motors, in fact in many ways it is better than Dino, but WVO is a problem waiting to happen! It has been known to clog pumps and cause symptoms like you are having.
 
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Old Jul 16, 2013 | 11:22 PM
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I have been running a light WVO blend when it the issues started, had run a heavier blend of WVO/Gas/Diesel for 4K miles but since the bounce started, straight diesel. Almost seems worse on just diesel. Got a little increase in power on the regular diesel.

Main reason for the engine swap is the 6.9 burning oil, its blowing smoke on acceleration more so, I can burn a quart in 80 miles now.

Hope to finish engine swap by this Saturday, going to start a 3500 mile trip early on Wednesday.
 
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Old Jul 16, 2013 | 11:35 PM
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Yeah that's what I thought, I would take this thread over to the alt fuel forum. If you are running wvo improperly, it can cause all kinds of problems. have you tried a diesel kleen or atf flush yet?
 
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Old Jul 16, 2013 | 11:47 PM
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while not the usual use of WVO, been running the same mix in my work truck (uncles work truck I use for the runs, he got the blend recipe and its the only mix he wants used), although the work trucks are powerstrokes vs my IDI.

I usually put 2-stroke motor oil with the diesel rather than the red ATF but I'll put some ATF in for the trip home.

I keep an extra fuel filter in the truck + the strap wrench and diesel to prime it so road side changes are possible if needed.
 
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Old Jul 17, 2013 | 12:21 AM
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I usually put 2-stroke motor oil with the diesel rather than the red ATF but I'll put some ATF in for the trip home
I'm not talking about a mix! This is a purge! Pull your fuel filter, drain it and fill it with either ATF, Diesel Kleen, Or another diesel additive. (I use Diesel Kleen, but ATF is proven as well) Start it and let it run for about 30 to 45 seconds, then shut her down to sit over night. The next day, drive her like you stole her! heavy on the gas and high RPM's for a while! It can do wonders!
 
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Old Jul 17, 2013 | 01:26 AM
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Will give it a go then when I get off work.
 
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Old Jul 18, 2013 | 01:18 PM
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Refilled the fuel filter with atf, ran it 45 seconds, shut it down for 6.5hrs (got home late) started it in the morning (took a bit, glad I have manuel plugs), ran rather well once started, refilled the filter with atf, ran another 45 seconds, it will be about 4 hrs till I drive it anywhere. Thanks for the advise, just one more bit of knowledge I have for working on these engines
 
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Old Jul 18, 2013 | 01:52 PM
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What type ATF did you use, dextrin or type F?

Steve

86 F-250, sc/lb XLT, 6.9L, C6, 3.55 ltd slip diff
 
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Old Jul 18, 2013 | 01:55 PM
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Type F as I was reading on here that it is the best kind to use.
 
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Old Jul 18, 2013 | 02:05 PM
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Thanks, for the quick reply, need to do this to my truck.

Steve
 
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