7.3 Missing throughout rpm range
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Senior User
Joined: Feb 2004
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From: Halstead, KS
7.3 Missing throughout rpm range
hello guys, I got a question. My 88 F250 w/7.3 has been idling a little rough since I got it, and now its a little worse. I just replaced the fuel filter, and filled the filter with diesel kleen in hopes of making it better. Its had a slight drip under the fuel filter, on the valve cover. I tightened everything, even the drain valve on the botton, new o ring on the water seperator part, its tight, ad the filter itself is tight. Maybe the filter header is cracked? Would this slight leak cause the truck to run rough? I figured a slight miss but not as bad as it is. The miss itself, is almost cyclic.... or rythmatic, as in, it isnt constant, it fades in and out, sometimes how an out of balance tire is, the vibration fades in and out. I did the return line tsb deal, cut it and plugged it, the line that ran to the filter header, and plugged the header with a fine thread bolt and no improvment. yes it was leaking fuel before I did any of this, so dont say that I caused it...lol Is it air in lines? faulty injector? whats going on?
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Senior User
Joined: Feb 2004
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From: Halstead, KS
Ok I bled it out and no improvement. When I got to the injectors, each time I cracked any of them, it changed the idle dramatically. That tells me that my injectors may be working fine. If one was streaming instead if misting the fuel, it might have not made much of a change when it was cracked. could it be the IP? Thsi truck is nearing 200,000 miles and Im sure it has the original IP and injectors in it. It runs fine and has ZERO smoke. It revs great and has lots of power. I cant imagine its an injector or IP, butmaybe so.
Post Fiend
Joined: Nov 2004
Posts: 5,638
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From: Manitoba
Visit..... http://www.intellidog.com/dieselmann/idi.htm and read all about the air in the fuel system problems, also the air intrusion points on the filter header, any wet spots most likely a leak......... but air will enter where diesel will not exit......
Have you listened to the intake noise with the filter removed, any "loud" woof woof from there. There will be a slight woof as the pistons intake air. What about the tailpipe any chuffing/crackle from it at idle or acceration.
Next thing would be to loosen the injector fuel line 1/2 turn one at a time to see if that one makes a difference in engine performance, no or little change would indicate a possible bad injector......
Have you listened to the intake noise with the filter removed, any "loud" woof woof from there. There will be a slight woof as the pistons intake air. What about the tailpipe any chuffing/crackle from it at idle or acceration.
Next thing would be to loosen the injector fuel line 1/2 turn one at a time to see if that one makes a difference in engine performance, no or little change would indicate a possible bad injector......
Last edited by PLC7.3; Feb 5, 2007 at 05:36 PM.
Posting Guru
Joined: Oct 2005
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From: Powell River B.C.
If it has 200K on original injectors and IP then its doing remarkable. If it were my truck I would do a compression test to verify all cylinders (ie no burned valves, or bent push rods etc.), then I would install a set of new or rebuilt injectors, but to be honest, with those miles on original equipment, do yourself a favor and just replace or rebuild your IP and injectors. You will be pleasantly supprised at the performance increase you didn't know you were missing. IMHO.Good luck.
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