Rough Idle

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vtefire

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Ok please help. I have replaced everything on my 2004 Ford Expedition 4.6L, everything meaning, coils, spark plugs, EGR...runs a little better, but when it is cold outside it is difficult to start. Once started it runs with a very slight hesitation. I have hooked it up to a monitor, no codes and no check engine light. So does anyone have any idea. My expedition has over 123000 miles and has been running great since I changed the fuel filter and found out i had bad gas. A new one was installed and like I said at the top, replaced the coils plugs and the EGR as of yesterday. Runs strong when warm, with a slight hesitation when you give it gas. I refuse to take it to a dealer do to they want a fortune. Any suggestions would be helpful, thanks.
 

Lane24

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Vtefire. Have you read the first page of this thread? Have you checked your vaccuum assembly, your IAC, cleaned your MAF sensor... or some of the other things mentioned. All good places to start.
 

vtefire

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Yes I have read all the threads. I have checked all my vacuum lines but I have not checked my MAF sensor or the IAT sensor. I will check those. thx
 

strokin393

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Ok my truck idles but has a miss to it so I unhooked each injector on pass side one by one and it made no dif, it ran the same. I did same thing on driver side and it did what it should do, idle down. I changed the 4 injectors and one of the coil packs on pass side and still the same. I changed fuel pump, plugs, filters, plugs, and cleaned maf, and tb. I don't know what else to check. The truck backfires when I start it after its already been running. I think because its not burning all the fuel. What do I check next? I already checked hoses for vacuum leaks and don't see any.
 

strokin393

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And pass side exhaust covered with oily gas inside it pretty bad
 

SC-Surfer

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OK, I have a 98 Expedition in the shop with the same problem. 4.6L Right side miss fires - Other mechanic is working on it. He went through all the same steps as you (It has been to 3 shops)

So we pulled the valve cover and what did we see? 2 rockers were sitting on the head. Placed them back on, drove it and same thing happened.

Not quite sure if its sticking valves or weak lifters. We did Seafoam the intake. Still ended up throwing the 2 lifters.

Only seen this once before on a V6 Jeep Liberty. That turned out to be a broken exhaust spring.

I would pull the valve cover and have a look. (Oh what fun Ford made that)

get yourself a LED flashlight at Lowes or where ever. Trust me, your going to need it to check the springs.
 
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METALLICA

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guys can you show me where the iac valve is located? i think my truck needs its iac some cleaning, tnx..
 

Lane24

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Where the red arrow is pointing. The pretty silver thing. It's an old pic from before I got the body lift. Much easier to get a t now.

SANY1187.jpg
 
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