ROUGH IDLE UNTIL FULLY WARM

LincolnSedan

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Have replace many tune up items like coils, plugs, v cover gaskets, upper timing chains, new denso premium o2 sensors seem to be a bit smoother idling and driving when warm. car starts in all temps, has power, no bog, no oil consumption, now loss of power. when cold it has a rough idle. after 02 sensors seems like idle evens out when fully warm. have not started playing with fuel injector or anything like sensors. any ideas on what may cause rough idle on a 3.9 colder motor? do think coils are fairly good based on general driving.
 
I would also look at the throttle body elastomer coated metal gasket if the rubber coating may have contracted enought to leak. This also applies to the intake manifold gaskets i use Dei 1500°F degree silicone spray to respay the metal gaskets and mating surface after 1500 grit paper to polish/clean the aluminum before spraying.
 
Hello thanks for the info. Do you think this will entail replacing both throttle body and intake gaskets at the end of the process to rule these out? It seems like the procedure you mention above is prep for the new gaskets? It looks like the new gaskets have a paper piece and o rings for both the tb and the intake. I could see how there may be a possible vacuum leak until the car got to operating temp. It seems to do that even now. The 02 sensors did seem to improve the idle a bit, they had 158k on them.
 
Have replace many tune up items like coils, plugs, v cover gaskets, upper timing chains, new denso premium o2 sensors seem to be a bit smoother idling and driving when warm. car starts in all temps, has power, no bog, no oil consumption, now loss of power. when cold it has a rough idle. after 02 sensors seems like idle evens out when fully warm. have not started playing with fuel injector or anything like sensors. any ideas on what may cause rough idle on a 3.9 colder motor? do think coils are fairly good based on general driving.
 
hello, there are no codes that I am aware of. I have a basic code reader, there is no check engine light, no strange fuel consumption. running premium, does not matter for warm up.
 
the fuel pump was replace a while ago would have too look at mileage but probably replaced at 50-60k original miles. i replaced the filter very recently.
 
One weakness of long time service i saw was the engine ventilation of the snap o-ring hose connectors. The materials are high temp tolerate but does it maintain a seal over long term? One other issue was the oil mist collection in the intake manifold. A catch can is the device that seperates the air and oil. The space is very limited under the hood to place one. So the hydrualic resevoir is a mirror image of the power steering resevoir, so it was used with aluminum air line quick disconnector for removing to empty the mist oil. The engine ventilation lines were re-routed to the catch can and the ventilation input behind mass air sensor. Three eights viton tubing was use for heat resistance. Maybe when you do the valve cover gaskets you have opportunity to tap a pipe thread for the ds valve cover vent port. This engine does not have a typical pvc valve but a 0.030" diameter orifice to regulate the air flow into the intake manifold.

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the pump was replaced, a ways into the cars life, it does not have any issues with power, noise, sputtering, stalling, cutting out, has plenty of power under load, up hills. what about vacuum leaks?
 
I had a cold miss issue a while back. If I drove it for 5 minutes and shut it down, it would be perfect on restart. ended up being the cylinder 1 fuel injector. I chased it for a long time because I was sure it wasn't the fuel injector. Why would it recover when warm but only after a restart? I don't know but that's what it was.
 
I thought about fuel injection, pull power wires, see if it mattered. I will try to turn it off when cold but do not think it will recover.
 
seem to be a bit smoother idling and driving when warm. car starts in all temps, has power, no bog, no oil consumption, now loss of power. when cold it has a rough idle. after 02 sensors seems like idle evens out when fully warm.
Normal in colder weather in colder climates. It should settle down and smooth out after a couple minutes. Mine does it every winter
 

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