Please help,Very rough Idle

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Oct 17, 2007 | 01:36 PM

rbpems

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Please help,Very rough Idle

I'm relatively new and I don't post a lot but I like to read the other posts for info on similar problems to mine. I used to use a mechanic but started doing the work myself because I got better results at least for the minor stuff. Yesterday I stopped at the store and when I restarted the truck it was idling very rough and the RPM's were surging on and off. It ran great just before that. When I give it throttle it goes away and runs fine while driving w/throttle on but bad w/throttle off. I have had a slightly rough idle for a while but this is real bad. By the way, it's a 93' E350 w/7.3 NA and 280000 mls. Any advice would be greatly appreciated.

Thanks
Rick

Oct 17, 2007 | 08:48 PM

Dave Sponaugle

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From: Nutter Fort, WV

Are you running any fuel addatives?
Have you changed the fuel filter recently?

Any chance you had just bought some bad fuel?
Have you drained the water seperator recently?

Oct 17, 2007 | 11:55 PM

goatz

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From: Mission BC CANADA

I just had the same problem yesterday and this morning i bought some power cleaner and ran a whole bottle threw it with half a tank seemed to help alot but still was idling really every so often then i filled up at a diff station and it hasnt idle bad since
I think it was bad diesel

Oct 18, 2007 | 10:53 AM

rbpems

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I put a half quart of 2 cycle in and 8 ounces of Howes injector cleaner and filled the tank. Some times I alternate and use Deisel Kleen. I used half the tank of fuel already. Would water separate and lie on the bottom of the tank? The fuel filter was changed about 8,000 miles ago and I didn't know I could drain the water separator. How do I do that? Thanks for the reply.

Oct 18, 2007 | 11:24 AM

PLC7.3

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From: Manitoba

Check the fuel for gasoline......if you can drain some out. Put some in a small tin plate, if it lights with a match it's not diesel. You may smell it also....... What is your hot (curb) idle set at should be 650 in gear AUTO, 650 in nuetral for manual.

Check the lift pump.....

Do a pressure and flow test of the fuel pump at the Schrader valve on the filter header (FSS- fuel shutoff solenoid disconnected on IP). Remove the tire valve core and hook a hose and pressure guage on it should see 4-6 psi when cranking. Then do a fuel quantity test same place, should see 1/3 pint in 10 seconds of engine cranking, route fuel to a suitable container with a hose.

If there is a problem with the lift pump and you are changing it, ensure the new pump comes with instructions as to correct installation procedure if it is the newer model pump with the almost straight arm.

Last edited by PLC7.3; Oct 18, 2007 at 11:26 AM.

Oct 21, 2007 | 07:39 PM

rbpems

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I changed the fuel filter and filled the filter with Diesel Kleen. The truck still idles very rough but doesn't seem to surge as much. I opened one fuel line at a time and the rpm's would drop for every one but the #4 cylinder(I think). It is the 2nd from the front on the drivers side. It has some kind of extension on the injector. I'm going to pull the injector and have it checked. Hopefully that's the problem. BTW this is the first time I'm working on a diesel fuel system. Reading all of your posts is making it easier to try and do this stuff myself. I'm having fun. Thanks for all your posts.

Rick

Oct 23, 2007 | 01:11 AM

goatz

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From: Mission BC CANADA

mine is still doing the rough idle but so far only seems like when i am on the rear tank, would it also run like this if the system is getting air in it?

Cause the other day when it did the rough idle right when i started it up and then it stalled and when i tried to star it again the motor just turned over and over and then i pushed the schrader valve at the filter and got my G/F to turn over it over and nothing came out at first and then fuel started comming out then it started right up.

Also when it does start idling ruff i give it some throttle for a couple of seconds and it smooths out.

to me it seems like the fuel is bleeding back casue an air pocket in the fuel filter.

anybody got any ideas?