Smitty98RT

Ok my 5.0 is slow to start. When I first crank it up it has a very rough idle once the motor has been running about a minute it It runs perfectly. It didnt used to do this. So far I have disassembled and cleaned the MAF and the IAC valve and put all new plugs, plug wires and distributor cap in. The plugs and plug wires are Autolite platinums and the new cap and rotor is MSD. I also have the MSD 6A ignition. Any ideas about what to do next?

mcfomco

Is the fuel pump making any more noise than normal sound like it might be bleeding off pressure over night.
Try cycling the switch a few times before you start it and see if that helps if it does expect to replace the pump soon.

grabbem88

i have the same problem...but if i turn the meter it starts fine...but idles weird when i come to a stop.

5.0 MPG

Smitty,

I have the same problem and have basically done evrything you have X 2.

https://mustangforums.com/m_1316574/...tm.htm#1318333

Im in the sme boat with you. I dont think it the pump however cause mine is new.

MC, does tank fuel pressure affect idle?

grabbem88

you can chk your coolant sensor?..sometimes it acts up.

5.0 MPG

Grab,

You may be on ti something here cause I dont get a reading at all in the cluster. How about you Smitty?

grabbem88

if you are like me...lazy in the coolant flush area..the sensor probably has calcium deposits all over it..

my city water is nasty so yeah use distilled when you have a chance

mcfomco

The preesure I am referring to is the fuel rail pressure bleeding down back through the fuel pump to the tank. Its not gonna cause tank presure to rise any just not enough fuel pressure to run the engine smoothly on initial start up. Ford has an issue with some evap systems building to much pressure and creating a vacum in the tank on not allowing the pump to supply to the engine. But thats only an issue form driving long distances the fix for this is a vented fuel cap which will not allow the tank to create a vacume on the fuel system and starve the engine.

Smitty98RT

You said yours does this every time hot or cold, Mine only does it when Im starting it from cold iron. If the engine is the least bit warm, its fine. Tell me more about why the coolant thingy could be my problem. Cuz I have been known to run str8 H20 in the radiator I bet my sensor is covered in calcium. Also this vacuum, could it be broken by taking off the gas cap and putting it back on before initially starting the car?


Actually I went out there and vented the tank and replaced the cap and then turned the key to RUN and for a second you can hear the fuel pump kick on for a second. It does this each time the key is put in RUN. Actually you wanna know what its like. Go unplug your MAF and start your stang see how crappy it runs. Thats the way mine runs for the first 30 seconds then it shapes up to perfection.

AdderMk2

NO WONDER WHY... get yourself a 180* thermostat and run some 70/30 water to coolant mix. and replace that coolant sensor.... your car is running in its starting table all the time. it porbably thinks its liek below freezing.... Dont hack your car.... fix it right... running JUST water will cause you to replace your water pump soon too