99 Windstar hard to start when hot

[Gillbro]

I have searched as best I can to see if there was a similar thread on here but didnt find anything.
On my 99 windstar 3.8 after driving in warm or hot weather or extra hard driving after shutting the van down and waiting around 15 minutes I will try to start it up and usually have to feather the throttle to keep it running until 5 to 10 seconds go by then the van runs fine. Sometimes it will set the ever so common 171 and 174 codes but not always. This problem wont happen in the winter or during cool weather. Also I have replaced the intake gaskets, valve cover, and plenum O-ring/bolt kit.

I also replaced the MAF with a used one and replaced the fuel filter neither of these had any affect on the problem.

When watching the data while idling it looks like the long term fuel trim is way up and can reach 20+ percent. I am not a actual mechanic but have a pretty good background but I am totally lost as of right now. Can anyone please help??

[12Ounce]

There are a number of critical relays that may not be fully energized at start-up ... have you read battery voltage during cranking?

[tomj76]

I have a similar problem, that I have not yet resolved, but I think I understand it's cause.

I believe that my fuel lines are passing too close to the exhaust lines, or are not properly shielded from the exhaust heat. This is causing the fuel in the lines to boil (vaporize) while the car sits after running. When the the vaporized fuel enters the fuel rail, it throws off the fuel/air mixture, because the injector timing is calibrated for liquid fuel, and the engine runs lean. This leads to high fuel trim readings, and the PCM is trying to correct for the lean condition.

After the engine runs for 1 - 2 minutes, the fuel pump has driven enough fuel through the loop to displace the vaporized fuel, and cool the lines down to prevent any futher vaporization of the fuel. Once the fuel is liquid, the engine settles down and the fuel trim returns to normal.

When this occurs in my case, I can hear a "bubbling sound" from the fuel tank when I first turn the key on (if my seat belt is buckled and the radio is off), and sometimes I can hear it over the engine noise after the engine is started. I have found that I can cycle the key switch a few dozen times to clear out the fuel vapor and avoid the CEL from the lean condition. The only codes I get are P030x codes, indicating the misfires.

[Gillbro]

I have not yet tested voltage, I will do that soon and repost. And I will check the closness of fuel lines to a heat source.

Thanks for the info, if any other ideas fire away.

[Gillbro]

The voltage at the battery and main fuse/relay junction is plenty during and after cranking. The fuel lines are routed propper away from any heat source.

The fuel pressure is 32lbs when running and around 40lbs when the throttle is given. after shut down the pressure rises to around 40lbs (guessing expansion) then over different periods of time will drop to around 20lbs while sitting.

Still trying....

[Gillbro]

[quote=Gillbro;6381994]The voltage at the battery and main fuse/relay junction is plenty during and after cranking. The fuel lines are routed propper away from any heat source.

The fuel pressure is 32lbs when running and around 40lbs when the throttle is given. after shut down the pressure rises to around 40lbs (guessing expansion) then over different periods of time will drop to around 20lbs while sitting.

Swapped the MAF sensor and no improvement. It only happens when the van has been driven aggressively and when its hot out after being shut down for 10 - 15 minutes.
Please help with any other ideas. Thanks!

[wiswind]

My '96 would sometimes run rough when restarted after being shut down for around 10 minutes......never did know what caused it.
It would be OK after about 1 or 2 minutes MAX......

[12Ounce]

I would try a new relay in the PCM position.

Also, test all the test points on all the battery box fuse tops ... see if any are a bit low.

[Gillbro]

I rotated (swapped) all the under hood relays just to see if I had a weak or intermittent one to no avail. The voltage after a another quick check at the relay block shows no signs of drop anywhere easy.

It is almost like one of the injectors is bleeding down when hot and sitting. Even though its shows lean it acts like its flooded out for a few seconds.

Off to the next barage of tests. If anyone wants to add, by all meens.

And Thanks to all who are jumping in!!

[tomj76]

Have you checked the EGR ports in the lower intake manifold? I once has a problem where my Windstar ran rough on restart, and it cleared up after cleaning the EGR ports. You have to remove the upper intake manifold to do this.

[Gillbro]

Yep they are clean I have had it open twice now. I just cant figure it out it is only bad when its hot out, or driven hard when warm out. If it is cool or cold outside all is just fine....

[perrytime]

see my updated post on my thread, in ummary, I would throw a IAC and TPS at it.

[Gillbro]

What thread am I looking for?

[perrytime]

this post

Hot soak start rough idle

But I see your problem is different, I have read a Ford TSB that says IAC can cause your issue

[Gillbro]

Thank you for the info Ill do some more checking and repost as soon as it gets hot enough up here.