2002 Taurus hot re-start rough idle

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2002 Ford Taurus with the 3.0L Vulcan engine. Car runs fine most of the time but after a long drive, park for 20 minutes or so and upon re-start it runs terrible for a few minutes then recovers to run normally. Recovers faster if you race the engine. Doesn't throw any codes. After much internet reading, my conclusion is it's a vapor lock problem with the fuel vaporizing inside the fuel rail. I'm guessing there's a leak somewhere in the fuel system allowing the pressure to drop which would lower the boiling point, maybe a leaky injector? Question is how to troubleshoot this? I can put a pressure gauge on the fuel rail and see how long it holds pressure but what should that look like?

This is a return less fuel system so any vapor that forms has to be passed through the injectors, right? We've been running ARCO gas so we'll try a brand name fuel to see if that helps, perhaps the boiling point will be a bit higher than ARCO who like to use a lot of ethanol! Seems like these Fords are kind of famous for this problem and people throw a lot of parts at it without solving the problem...
 
Vapor lock is not likely since there would normally be fairly high pressure in the fuel rail, unlike a carburated engine. Hang your fuel pressure gauge on the service port, Key on, engine off fuel pressure will be around 43 psi. Engine running 36-38 and deadhead pressure of 55psi. The pressure should hold for a long time after you shut off the engine. A leaky fuel injector(s) can bleed down the pressure right away. A faulty pressure regulator can affect pressure all the time and there is a check valve with the pump. An EGR valve hangine open slightly can make restarting difficult.A coolant temperature sensor could also be sending the wrong information when warm too. You can connect a scan tool and see everything going on during operation. There can be many things which can cause this.Diagnose, don't start throwing new parts at it since that can get expensive and yield no improvement.
 
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Originally Posted By: Lubener
Vapor lock is not likely since there would normally be fairly high pressure in the fuel rail, unlike a carburated engine. Hang your fuel pressure gauge on the service port, Key on, engine off fuel pressure will be around 43 psi. Engine running 36-38 and deadhead pressure of 55psi. The pressure should hold for a long time after you shut off the engine. A leaky fuel injector(s) can bleed down the pressure right away. A faulty pressure regulator can affect pressure all the time and there is a check valve with the pump. An EGR valve hanging open slightly can make restarting difficult.A coolant temperature sensor could also be sending the wrong information when warm too. You can connect a scan tool and see everything going on during operation might point to something. There can be many things which can cause this.Diagnose, don't start throwing new parts at it since that can get expensive and yield no improvement.


Sorry,this is what happens when you type in the dark.Wouldn't let me delete.
 
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As you say lots of reports about vapor lock on this car and engine and a TSB's about it.
This can be a problem when a returnless FI systems is used. TSB Number: 15680 is applicable to your car it may or may not have a OBD II code.

If after check everything out and you still cant find the problem I would clean the injectors. PM me I can do this for you. Before doing that i would get some heat insulation and wrap the fuel rails and zip tie some around the injectors to see if it helps first.
 
Does any smoke come out the tailpipe when it is running bad? If like Kruse said an injector is leaking and filling the engine up with raw gas, you might see black smoke.
 
I have a 97 Taurus with the Vulcan that would do this same thing occasionally. I did quite a bit of troubleshooting before I swapped the Throttle Position Sensor from my spare parts stash and it fixed the problem I was having. I even had one morning where it almost didn't start.
 
Originally Posted By: mk378
Does any smoke come out the tailpipe when it is running bad? If like Kruse said an injector is leaking and filling the engine up with raw gas, you might see black smoke.


Not that we've noticed. I've read the fuel just goes past the rings and gets into the oil. I haven't done a recent UOA but that might show something...
 
Originally Posted By: DerbyDave
I have a 97 Taurus with the Vulcan that would do this same thing occasionally. I did quite a bit of troubleshooting before I swapped the Throttle Position Sensor from my spare parts stash and it fixed the problem I was having. I even had one morning where it almost didn't start.


Interesting, wonder why it would just be when warm? On your morning start are you talking cold or warm start? My problem is only after hot soak.
 
Originally Posted By: Scout1
Originally Posted By: DerbyDave
I have a 97 Taurus with the Vulcan that would do this same thing occasionally. I did quite a bit of troubleshooting before I swapped the Throttle Position Sensor from my spare parts stash and it fixed the problem I was having. I even had one morning where it almost didn't start.


Interesting, wonder why it would just be when warm? On your morning start are you talking cold or warm start? My problem is only after hot soak.


The morning it didn't want to start it was stone cold, but that only happened once. The rest of the times it was warm. It had sat for maybe 15-30 minutes. Ran like [censored] for a minute or so and then everything was good to go.
 
Originally Posted By: SirTanon
Perhaps a coolant issue, causing the head area to be abnormally hot?


That may actually be part of the problem. We've had lots of cooling problems with this engine as most have. Again, a well known problem on these is the cooling system is a mess with junk from the block casting floating around and gumming up the system. We've had to replace the heater core which was totally plugged and I suspect the radiator may not be working at full efficiency. However the temp gauge stays normal and it has shown no tendency to overheat, well at least not when we've had coolant in it. We had to recently replace the timing chain cover which was leaking coolant - another known problem with this design.

At any rate, I saw one post where a guy removed and cleaned out his radiator and it cured his hot start problem! I wonder if the head cooling passages might be partially blocked leading to an overheated fuel rail? So maybe you're right!!! I could always put a lower temp thermostat in... hummm...
 
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