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Q: Engine takes to long to warm up I've replaced thermostat already and it misses horrible till it warms up its a 4.9 engine

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Truck starts up in the morning and idles tight up then dies and misses and runs rough then warms up and runs good until i stop for a few minutes start it back up and it misses again until it runs for a few minutes

My car has 173000 miles.
My car has an automatic transmission.

These engines are known to get real bad carbon build up on the back sides of the valves. If you engine has a hard time getting to operating temperature then it will also cause the engine to carbon up even faster. Once you correct the engine not getting up to operating temperature by replacing the fan clutch if it is locked up. You will then need to remove the excessive carbon from the intake system ans valves using Ford combustion chamber cleaner or equal and allow the engine to suck it in to the intake when the engine is cold so the carbon will soak up the cleaner. Shut down engine and let sit for about 20 minutes and repeat process. Once this is done then start and run engine at 1500 rpm for 10 minutes to loosen any remaining carbon deposits. Once this is done then you may have to replace spark plugs and also should have the fuel injection system cleaned. The injectors get carbon deposits on them that cause the spray pattern to be incorrect and cause running issues. Have a mechanic like one from YourMechanic come to you to perform all these services and repairs.

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