Slightly erratic idle - Ford Powerstroke Diesel Forum

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post #1 of 13 Old 12-08-2008, 04:06 PM Thread Starter
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Question Slightly erratic idle

Gentlemen,
My 97 F250 has been idling funny lately. It fluctuates about 50 to 75 rpm, and sometimes it's just fine. Runs great otherwise. Changing fuel filter makes no difference . Is this a pre-cursor to impending doom? Any thoughts greatly appreciated. Idle fuel pressure is approx. 60 to 70 psi..

1997 F250 7.3L Krew Kab, Short box, Red&white
Banks Git-Kit, K&N Air Filter, Bypass oil filter,
Gutted Cat & muffler delete, 3 Pillar Isspro gauges: boost, pyro, trans. FPR shimmed, Marshall fuel pressure gauge under hood. 170K
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post #2 of 13 Old 12-08-2008, 04:26 PM
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50 rpm up or down?

Searching :
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post #3 of 13 Old 12-08-2008, 04:27 PM
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try the fuel plate mod? my dad has a 95 that does that a little only when first starting tho. sometimes longer than others. I have heard increse in line pressure helps idle issues with the OBS OBD1 computer system. Im sure a techie will know exactly what u need.

Built engine, rods, pushrods, cam, springs. Meth, turbo, injectors, fuel system, oil system. 3 disk billet, billet shafts built trans, 6.0 IC, exhaust, intake. Latter bars, gears, system, tint, HIDs. You know the typical stuff to make a 7.3 get out of its own way... dont brake.
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post #4 of 13 Old 12-08-2008, 04:35 PM Thread Starter
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It usually seems to drop DOWN just a bit. I'm not familiar with the fuel plate mod. Any thoughts on it possibly being the ICP sensor?

1997 F250 7.3L Krew Kab, Short box, Red&white
Banks Git-Kit, K&N Air Filter, Bypass oil filter,
Gutted Cat & muffler delete, 3 Pillar Isspro gauges: boost, pyro, trans. FPR shimmed, Marshall fuel pressure gauge under hood. 170K
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post #5 of 13 Old 12-08-2008, 05:09 PM
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im apt to say welcome to the wonderful world of the OBS. Mine does the same thing. These trucks were the first of any computer controlled diesel (well in '94.5 they were) so the control over the engine tends to be a bit slow so the computer catches itself. Mine has done it for three years so i wouldn't be to worried about it. Id be willing to bet you see it more prominently after a long highway run or pulling a good load. I just tell myself its black betty (my truck) not wanting to stop its champing at the bit. It sounds like fuel pressure and everything else is where it needs to be so like i said don't worry about it...keep and eye on it but don't worry about it. I know that its kind of annoying though.
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post #6 of 13 Old 12-08-2008, 05:25 PM Thread Starter
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OK, I think I can just live with it. Whats your take on a high pressure oil crossover? I've heard these can make idles smooth out. My engine also has a slight shudder to it while idling. And Turbodude, thank you for serving our country in the military!.. Chris

1997 F250 7.3L Krew Kab, Short box, Red&white
Banks Git-Kit, K&N Air Filter, Bypass oil filter,
Gutted Cat & muffler delete, 3 Pillar Isspro gauges: boost, pyro, trans. FPR shimmed, Marshall fuel pressure gauge under hood. 170K
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post #7 of 13 Old 12-09-2008, 06:27 AM
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doing the fpr shim helps some, but i know what your talking about. rpms kinda dip down a bit close to the 500rpm line, then back up. its similar to if the a/c compressor was coming on and back off.

mine only does it when the engine is cool


it'll be fine though

Typical cummins owner.

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post #8 of 13 Old 12-09-2008, 06:54 AM Thread Starter
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Thank you, T-Bone, I will try the FPR mod as I am familiar with that. Yep, same symptoms as you describe. I have a Marshall fuel pressure gauge mounted where the schraeder valve normally resides, so it will be easy to see what sort of a pressure reading I end up with. Thanks for the reply. Merry Christmas out there in NC. Chris

1997 F250 7.3L Krew Kab, Short box, Red&white
Banks Git-Kit, K&N Air Filter, Bypass oil filter,
Gutted Cat & muffler delete, 3 Pillar Isspro gauges: boost, pyro, trans. FPR shimmed, Marshall fuel pressure gauge under hood. 170K
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post #9 of 13 Old 12-09-2008, 12:03 PM
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let us know if it helps any

you will get a tad bit extra smoke too, i can flip my chip to stock and see a faint bit when i put the hammer down.

Typical cummins owner.

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post #10 of 13 Old 12-09-2008, 12:58 PM
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the cross over hose its okay not much of a difference little smoother on my 96
but easy to install but move the hpop line was a pain in the *** but a little more throttle response at higher rpm about 1500+

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