Running rich/Rough idle question

suprared89

Registered User
Guys,
I have posted here before with everything I have done to my car.
I think I may have found the problem. I wanted to get some expert input.
I checked my fuel pressure and am currently getting 35-36 psi at idle with fpr connected. When I test the fuel pressure the gauge jumps up to 45 psi with the pump running, when it shuts down, the pressure drops to 10 psi. My thinking is that the fuel pressure is too low therfore causing the ecu to see a lean condition then commanding higher injector duty cycle. This in turn makes it run rich and have rough idle in gear.
Am i crazy????
 
Sounds to me like you need to check for a large vaccum leak. What kind of vaccum do you pull at idle in gear? Fuel pressure seems alright to me, it would help if you could drive it with a visible gauge hooked up to see if pressure holds but I'm sure it will. How long does it take the fuel pressure to fall down to 10psi after you shut the car off? Maybe you have a fuel leak.
 
Ok, I just looked at some of your previous posts. I have seen a few wierd situations where a fuel pump, even though it built proper pressure was the culprit for a run problem like you descibe. There are a few things I would check before just throwing one at it though. The coolant temperature sensor, the air intake temperature sensor, and the BAP sensor are easy to test to make sure they are doing their job. These sensors send the computer iformation in relation to how hot air or coolant is. This can affect how rich the car runs. You could also have an egr problem, but I don't know a good test for that because I deleted it!!

http://fordfuelinjection.com/?p=3

Go to that website for information on the sensors I have mentioned. While at it, you can test the position of your tps sensor as well. You'll need to have a voltage tester for this. Any questions you have let me know.
 
I have checked every possible vacuum point for leaks. I have used carb cleaner as well as propane. I have replaced the ect that feeds the ecu. I have replaced both hego's as well. I have swapped ecu's, edis module, maf sensor. I have replaced the thermostat. I have gone so far as to lower the exhaust and run to see if cats were clogged. I just don't think there is anything left. The fuel pressure drops immediatelly. I also hear a gurgling sound in the tank when the pump shuts down. This leads me to this conclusion. What do you think?
 
I have checked every possible vacuum point for leaks. I have used carb cleaner as well as propane. I have replaced the ect that feeds the ecu. I have replaced both hego's as well. I have swapped ecu's, edis module, maf sensor. I have replaced the thermostat. I have gone so far as to lower the exhaust and run to see if cats were clogged. I just don't think there is anything left. The fuel pressure drops immediatelly. I also hear a gurgling sound in the tank when the pump shuts down. This leads me to this conclusion. What do you think?

Pull the vacuum hose off the fuel pressure regulator and see if there is any gas in the vacuum hose. I had a leaking regulator that took me over a year to figure out. Mine was holding good pressure when motor was running, but would imediantly drop about 20 psi when ignition was turned off, then quickly bleed off the remaining pressure.

This leak was dribbling fuel directly into the intake manifold and most was going into the two rear cylinders. An injector can also stick open and cause the same thing to happen.

David
 
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