Misfire at idle?
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Senior User
Joined: May 2008
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From: I live in Tennessee
Misfire at idle?
I was working on this truck that the guy said was missing at idle. Its a 95 PSD f350. At idle the truck shakes a little bit but after you give it fuel its gone. I did a cylinder contribution test and it came up P1111 system pass. Buzz test sounded good and strong. It seems like it does it when you rev it up then let off it struggles to find its idling rpm for a second or two then smooths out but still shakes the door about a 1/4 of an inch up and down when its open and the truck is running. No smoke coming from the exhaust whatsoever even driving it. Oh and when you put it in gear, no shakes at all, none.
Hotshot
Joined: Jul 2008
Posts: 11,231
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From: Thomasville, GA
Sounds pretty normal... it usually takes a second to find idle when you decelerate. The shake of a 1/4" really doesn't seem that bad.
I'd check the fuel pressure at the schrader valve on the FPR (beside the fuel canister). Also when was the fuel filter last changed? FPR screen cleaned (hole inside the fuel bowl on the driver side) you can clean it with a cotton swap with the cotton removed.
Oil changed recently?
I'd check the fuel pressure at the schrader valve on the FPR (beside the fuel canister). Also when was the fuel filter last changed? FPR screen cleaned (hole inside the fuel bowl on the driver side) you can clean it with a cotton swap with the cotton removed.
Oil changed recently?
Thread Starter
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Senior User
Joined: May 2008
Posts: 198
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From: I live in Tennessee
Does it both warm and cold. He just had the oil changed. I dont know about the fuel filters. I didnt know that screen exists. I will check that thing out. The oil pressure gauge is acting up. It bounces all over the place and when you rev the engine, the oil pressure goes down shakily. Seems like its not working right rather than the oil pressure actually doing that. Does the ecm use the oil pressure sensor as an input? 
Hotshot
Joined: Jul 2008
Posts: 11,231
Likes: 130
From: Thomasville, GA
The oil pressure gauge is a joke. More of an idiot gauge than anything. If the oil pressure was low the injectors wouldn't fire and the engine would shut off.
Check the wiring connector for the oil pressure on top of the High Pressure Oil Pump, front top pass. side of the engine. If it's loose it could throw off the reading.
I still say fuel filter, FPR screen, and fuel pressure. You can check the fuel pressure with a cheap tire gauge as long as it goes up to at least 80 psi.
If it's between 50 and 80psi it's good. If below, look up "FPR Shim" in the forum. Basically involves putting a BB in front of the FPR spring and it'll boost the fuel pressure. Just be sure it doesn't go above 80psi at idle.
Check the wiring connector for the oil pressure on top of the High Pressure Oil Pump, front top pass. side of the engine. If it's loose it could throw off the reading.
I still say fuel filter, FPR screen, and fuel pressure. You can check the fuel pressure with a cheap tire gauge as long as it goes up to at least 80 psi.
If it's between 50 and 80psi it's good. If below, look up "FPR Shim" in the forum. Basically involves putting a BB in front of the FPR spring and it'll boost the fuel pressure. Just be sure it doesn't go above 80psi at idle.
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