4.2l intermittent rough Idled
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4.2l intermittent rough Idled
I have a 1998 F150 4.2l and it started to have a rough idle sometimes, it comes and goes. I have replaced the spark plugs, fuel filter, fuel pump. It still does it and I was hoping that someone has seen a problem like this and could give me some advise on what was causing it.
Thanks for you help
Thanks for you help
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I have a 1998 F150 4.2l and it started to have a rough idle sometimes, it comes and goes. I have replaced the spark plugs, fuel filter, fuel pump. It still does it and I was hoping that someone has seen a problem like this and could give me some advise on what was causing it.
Thanks for you help
Thanks for you help
IAC
EGR valve - make sure it's closing all the way.
DPFE sensor - not likely, but IF it's defective, and telling the EGR valve to open at idle, that could cause it to run rough.
MAF Sensor
There's a good write-up here somewhere on cleaning the idle air controller - just search for it.
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ok update,
I have replaced the EGR Valve, the IAC Valve, the spark plugs, the plug wires, the Coil Pack, checked for vacuum leakes. The problem is still there. It comes and goes, starts out fine most of the time. Then out of the blue it starts to idle rough. It will go away most of the time on its own while driving, but sometimes stays through a few engines startings. I also have what sounds like a lifter knocking too.
Any help on this would be great.
Thanks
I have replaced the EGR Valve, the IAC Valve, the spark plugs, the plug wires, the Coil Pack, checked for vacuum leakes. The problem is still there. It comes and goes, starts out fine most of the time. Then out of the blue it starts to idle rough. It will go away most of the time on its own while driving, but sometimes stays through a few engines startings. I also have what sounds like a lifter knocking too.
Any help on this would be great.
Thanks
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ok update,
I have replaced the EGR Valve, the IAC Valve, the spark plugs, the plug wires, the Coil Pack, checked for vacuum leakes. The problem is still there. It comes and goes, starts out fine most of the time. Then out of the blue it starts to idle rough. It will go away most of the time on its own while driving, but sometimes stays through a few engines startings. I also have what sounds like a lifter knocking too.
Any help on this would be great.
Thanks
I have replaced the EGR Valve, the IAC Valve, the spark plugs, the plug wires, the Coil Pack, checked for vacuum leakes. The problem is still there. It comes and goes, starts out fine most of the time. Then out of the blue it starts to idle rough. It will go away most of the time on its own while driving, but sometimes stays through a few engines startings. I also have what sounds like a lifter knocking too.
Any help on this would be great.
Thanks
Hmmmm......check the rubber boot coming from the PCV valve. It's under the front of the upper intake manifold, just behind the throttle. It's hidden among the small coolant lines. At the other end of the PCV lines, the is a rubber hose that attaches to the rear passenger side of the upper intake - check it also. Sometimes, but not always, a leak in that boot or the rear hose will throw a P0174.
Fair warning: If you pull the PCV hose/tube assembly completely out, it's a P.I.T.A to get back in. Generally speaking, the whole mess is a pain to work on. I replaced the boot with an aftermarket from Dorman, and routed the hoses to the outside on top of the valve cover. I eventually went to a dealer and picked up the whole assembly for $39, a took off the bracket the mounts the EGR vacuum regulator and the DPFE sensor. It went in easily then, but I managed to break a connector to one of the fuel injectors.....
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Ill check that tonight and see how it looks. I have had it off once and it went back on pretty easily. Does anyone know if you unplug the MAF what the engine does, should it change idle or stay the same?
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Another update, now the truck is hard to start. It acts like the fuel line is draining back or not holding pressure. I have to pump the gas peddle to get it to start now. Could this be related to the rough idle that it has? I replaced the pcv, and the elbow and no improvement. I checked the fuel filter and it was clean, easy to blow through. I pushed on the valve on the fuel rail and gas came out while it was running, just didnt seem like it was very pressurized. Should I take a fuel pressure reading and if so what should it read? Also I have read that you can hook up a vacuum guage to check for a vacuum leak, how do you do this and where is the best place to hook into the vacuum system to test it?
Thanks again for any help.
Thanks again for any help.
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Ok so I did a compression test on the motor:
60 PSI in two cylenders, 90 PSI in the others.
I also found all the front intake manifold bolts only finger tight (dont think this would cause low compression, would it?), and the fuel pressure regulator had fuel in the vacuum line. I am planning on replacing the long block and any and all sensors that dont give me the warm fuzzy feeling.
Any suggestions on easy ways to pull the motor are appreciated.
60 PSI in two cylenders, 90 PSI in the others.
I also found all the front intake manifold bolts only finger tight (dont think this would cause low compression, would it?), and the fuel pressure regulator had fuel in the vacuum line. I am planning on replacing the long block and any and all sensors that dont give me the warm fuzzy feeling.
Any suggestions on easy ways to pull the motor are appreciated.
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