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

asked by on

My truck runs very poorly in the morning then runs better when warmed up until I shut it off and restart it starts missing again until it runs a little then runs better don't wanna idle in the morning

My car has 1730000 miles.
My car has an automatic transmission.

This engine uses a cooling fan clutch that controls the fan speeds on demand when the engine radiator starts to get hot if increases air flow to cool the engine down and slows the fan when it needs to increase the engine speed. If the fan clutch is locked up then it will not let the engine get warmed up. With engine cold and engine off see if the fan clutch allows the fan to spin pretty free with little resistance. If it is hard to turn the fan then the fan clutch needs replaced. For the rough running your engine running colder than normal will build up carbon deposits on the valves and foul out spark plugs. The carbon build up on the valves will absorb fuel when engine is cold and cause runs rough and misfires. You will need to de-carbonize the engine after cooling system repairs and may even need to have a major tune up done to correct misfires. A mechanic like one from YourMechanic can do all the repairs and diagnosis needed for you.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. 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

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: What could be wrong with my truck?

When you have a vehicle that is 27 years old it can be most anything causing the vehicle to hesitate. Depending on the engine you have you may have a sensor issue that is not working correct or a fuel...

Q: Misfiring and emissions leak in 2000 Ford Crown Vic

It all depends on what you think of the vehicle. These Crown Victoria can run for an awfully long time, but you'd want to find out what this misfiring is to keep this car up and going. If the misfiring...

Q: Radiator fan making noise when running

The fan motor turns very fast, and these motors do go bad after continued use; five or six years is a good life span, you made it nine years. I recommend having a mechanic such as one from YourMechanic, inspect...

Related articles

P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.