Flooding Problem With 1998 Mountaineer 5.0

[mlochala]

I have been trying to resolve several issues with my Mountaineer over the past several months. I have got most of the problems eliminated, however I still have an issue with this thing apparently flooding when it has warmed up.

When starting from cold, it cranks right up very well every time. But, if you run it for 15-20 minutes until it gets to good operating temperature and then park it somewhere and shut it off, when you attempt to crank it just a few minutes later it will not crank very easily. It struggles to reach idle speed. If you give it a stab of the gas pedal, sometimes it will smooth out, but at other times it will struggle to rev up and will even backfire. If you can make it to the road and start going down the road, it will smooth out and run fine. That is, until you turn it off and attempt to start it again.

So far, I have new plugs, wires, Motorcraft IAC valve, fuel pressure sensor, Bosch purge valve, coolant temperature sensor....seems like there is something else I am forgetting, but right off the top of my head, that is what I have done recently.

When I changed the plugs out, there were two on the passenger side bank that were very, very corroded, much more so than the rest of the plugs. It has been suggested to me that I might have an issue with one or more faulty fuel injectors leaking down when I turn it off. But, before I make that investment, I wanted to come here and ask at least once more if anyone else has an idea of what could be causing this.

I would appreciate your help very much.

 

[koda2000]

After you turn the engine off fuel pressure remains in the fuel rail for quite a while. If you have a bad/leaking fuel injector perhaps it's flooding the engine when it's warm. Another consideration, though I think perhaps less likely, is a bad coolant temp sensor. If the PCM thinks the engine is cold when it's not it would be like running a carburetor engine with the choke on.

 

[MDmounty]

I would double check my spark plugs to make sure you put the right wires on the right plugs. I swapped my 7 and 8 plug wires the other week and it backfired and ran terribly, rough startup. That may make your problem a bit better if two were accidentally swapped

 

[mlochala]

After you turn the engine off fuel pressure remains in the fuel rail for quite a while. If you have a bad/leaking fuel injector perhaps it's flooding the engine when it's warm. Another consideration, though I think perhaps less likely, is a bad coolant temp sensor. If the PCM thinks the engine is cold when it's not it would be like running a carburetor engine with the choke on.

I have already replaced the coolant temp sensor. I am leaning toward the leaking fuel injector, but why would it only do it when it is warm?

 

[mlochala]

I would double check my spark plugs to make sure you put the right wires on the right plugs. I swapped my 7 and 8 plug wires the other week and it backfired and ran terribly, rough startup. That may make your problem a bit better if two were accidentally swapped

I replaced the plugs and wires very carefully, one at a time. If I had accidentally swapped wires, it wouldn't run good at any time. As it is now, it only has issues when it is warm and I start it up five to fifteen minutes after turning it off.

 

[koda2000]

I have already replaced the coolant temp sensor. I am leaning toward the leaking fuel injector, but why would it only do it when it is warm?

Two reasons:
1. When the engine is cold the fuel pressure in the fuel rail has dropped and no additional fuel is leaked into the engine. Excess fuel, which leaked into the engine while warm, has evaporated.

2. The PCM adds additional fuel when the engine is cold, so the effect isn't noticeable.

Pull your oil dipstick as smell the oil to see if it smells like gasoline. Might be another sign of a leaky fuel injector.