Is the check engine lamp on? I would like to think it would be, but I have seen some serious engine problems that did not illuminate the MIL ( malfunction indiactor lamp ) in the past. Checking fuel pressure is always a good idea, I personally like the clogged exhaust theory off the top of my head. From your short description, what stands out to me is that you specify 3000 rpms. Clogged, or should I say restricted exhaust systems tend to make the efficiency of the engine much worse at higher RPM's due the the amount of air trying to flow through it. I would be even more suspicious of a restricted catalytic converter if you have had any repairs made in the past or recent past for cylinder misfires. Some more details about the vehicles current state of affairs and recent repair work would help out. How many miles, typical driving conditions for the vehicle, anything helps. Also, the mass airflow ( MAF ) sensors on Ford vehicles have a very large influence on fuel control, and when they get excessively dirty can cause symptoms similar to your description, but I can't say that I have ever had one stall or get close to stalling because of a faulty or dirty MAF. The typical main concern with a MAF problem is lack of power. Good luck to you, ask more questions if you need.
Thanks my friend,Also the engine light is not on,I have 150000 miles and have had no issues,I drive a half an hour to work and back,and thats it,How would i check the catalytic converter?i see you have a Shop??
Well, there are special tools that you would use, the easiest being a scan tool. They do make what is known as an exhaust backpressure tester, it is basically an adapter that screws in in place of the oxygen sensor. The other end connects to a pressure gauge, when you run the engine at various RPM's, you note the pressure reading on the gauge. Problem is, this tool can be hard to install on some vehicles due to the location of the oxygen sensors, especially if you are doing it at home, and this may not be a case of exhaust restriction at all, we are still assuming that it is a cat restriction at this point based on your description. Honestly, your best bet is to take it into a shop you trust, tell them the symptoms you are experiencing, and let them take it from there. A good quality scan tool and a knowledgeable technician should be able to find the root cause of your issues fairly quickly and at a reasonable price. It may also help to drive it some more, if the MIL is not on, it may be because the ECM has not had enough time with the problem present to turn it on. Having the MIL on when you take it in for diagnosis typically helps quite a bit, so if you can drive it SAFELY for a few days, it wouldn't necessarily be the worst thing in the world. I don't think I would drive it for more than a few days or more than around 100 miles in it's present condition though, so as to avoid damaging any other components.