Rough idle after hot soak restart

[serge_saati]

I have a Taurus 2002 with the 3.0L OHV Vulcan engine and I had a "Hot soak start rough idle" intermittent issue. It happens after I restart my warm engine in winter, it runs rough for 30 seconds and I also feel a 2 seconds delayed accelerator response like if I had low fuel pressure. Rough idle is about 400-650 rpm.

I also had once check engine light and the codes P0300 and P0316 and they clear up after 5 minutes of driving.

I've searched infos thru Ford TSB, and I found a TSB for that issue saying that idle can be rough after a hot soak start with winter fuel and there's nothing we can do for that.

TSB numbers are 02223, 15680, 15745 and 15915:
http://www.aboutautomobile.com/TSB/2002/Ford/Taurus/Gasoline+Engine
http://www.automd.com/recall-tsb/sea...rt+taurus+2002

The cause of the problem is when fuel remains too long inside hot injectors and fuel rail, it becomes too hot and vaporises within the injector and rail, especially with very volatile winter-blend fuel when it's relatively hot outside for winter, so it causes vapor lock and fuel starvation because fuel has more difficulty to flow because of the vapors, so that causes misfire because of the lack of fuel injected, until vapor is cleared from injector or condensated and cold liquid fuel arrives and fuel debit increases.

So when it runs rough, we should press to the gas to quickly clear and condensate the fuel vapor from the injectors and bring cold fuel at higher rate and higher pressure from the fuel pump to cool down the injectors. And don't temporary turn off the engine for nothing until arriving at destination.
The best is go to a drive at highway. It also help to cool the engine with fresh air inside the engine compartment and having fuel at faster rate and higher pressure to condensate fuel.

Also before starting, cycle key on(1 sec)/off/on(1 sec)/off/on(1 sec)/off, then start. It will increase fuel pressure and thus, fuel boiling point. So will help the vapor to condense into liquid.

Taurus' engine heats a lot, it doesn't have a very efficient cooling system as Chevrolet Impala for example. So the fuel has more chances to boil and cause problem.

I've also searches more infos thru the internet, and I found out that Jeep also has these issue with their 1999-2004 Cherokee, Wrangler, Grand Cherokee and they make a TSB including a solution for the problem.

Here's the official TSB from Jeep: http://www.wjjeeps.com/tsb/tsb_wj_1803103.pdf


Jeep has the same problem as Ford, just like other car manufacturers like Acura, Honda, Volkswagen...

They said that the problem can be aggravated by the use of fuel contening ethanol.
Because ethanol fuel has a lower boiling point, thus it's more volatile than pure gasoline.
So I suggest to NOT use fuel blend with 10% ethanol if you have the choice. I suggest high octane premium fuel w/o ethanol.
High octane fuel has lower boiling point and it doesn't contain ethanol on certain stations, where regular contains up to 10%.

Jeep explains in the TSB how to fix this issue. They suggest to install an insulator sleeve wrapped around fuel injectors.
Solution might work with Ford engine as well.

I suggest to wrap a cutted insulator sleeve or rubber hose around all injectors and fuel rails.
Then attach the splitted sleeve with tape or tie-wrap.

That's an example of fix for a Cherokee 2000. The dealer installed a heat shield around injector #3 and a shield on the intake manifold:







Heat is irradiated from lower intake manifold to fuel injector and rails, causing the injectors, rails and the fuel to be very hot after a long drive.
So when vehicle is parked for 10-20 minutes, the fuel remained in hot injectors and rail become very hot and vaporises causing rough idle.
Wraping insulator sleeve (heat shield) around the injector protect it against heat radiation.

Taurus 2002 with 3.0L OHV and Windstar with 3.8L engines have metallic fuel rails. Metal is very heat conductive, so it become hot when it's close to heat radiation.
Metallic fuel rails are close to hot lower intake manifold of the engine so they become very hot.

This problem affects also Windstar and Ford trucks vehicles.

The problem is vapor lock. It happens when we use high volatile winter-blend fuel and we start the engine when engine is very hot and it's not too cold outside.
Also sometime after a long drive into traffic, because engine heats up and fuel debit is low. And there's not enough fresh air flowing into the engine compartment.

It occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system. This disrupts the operation of the fuel pump because it pumps less liquid to maintain pressure and fuel has more difficulty to move, causing loss of feed pressure to the fuel injectors.
There's more resistance in fuel rail because of the fuel vapor pressure. Fuel should circumvent the vapors to arrive at the injectors. The fuel flow is reduced.

http://en.wikipedia.org/wiki/Vapor_lock

A vapor lock is more likely to develop when the vehicle is in traffic because the under-hood temperature tends to rise. A vapor lock can also develop when the engine is stopped while hot and the vehicle is parked for a short period. The fuel in the line near the engine does not move and can thus heat up sufficiently to form a vapor lock. The problem is more likely in hot weather.

[serge_saati]

shorod, can you make this post sticky?

[ronhud99]

just took my 06 tarus to the dealer to have that problem fixed car starts up if u restart after a few minits but after 20 u have to hold gas petal down for 8-10 seconds then it starts its 3/37 2017 i have pulled out the rest of my hair trying to figure this out thanks loads ps 3.0 ohv motor ron

[shorod]

When you say you have to hold the gas pedal down to get it to start, are you just holding it enough to open the throttle valve a bit, or do you have to hold it to the floor? If just a bit, you might have a throttle plate that is carboned up on the back side and needs a good cleaning. If you hold it all the way to the floor, that will put the car in "clear flood" mode which shuts off the fuel injectors while the engine is cranking and would suggest you have one or more fuel injectors that are leaking fuel in to your cylinders, and after the car sits for 20 minutes, enough fuel has leaked to flood the engine.

-Rod

[ronhud99]

about half way down works ok going to try covering fuel rails and injecters
ron

[mustangame]

My 2000 Mustang (3.8L V-6 Engine, manual) does this as well. Had to replace the fuel pump the first year it started happening as it quit completely.
I tried a bottle of HEET last winter in a fresh tank of gas, and it seemed to help. Going to try it again on my upcoming tank as it started acting up again over the weekend after a longer drive than normal.
I will save this post for future reference... I didn't realize vapor lock was still a thing, but it describes what's happening exactly.
Thank you for the post!