About my car

Once you're in third or fourth gear and the engine is warmed up, the torque converter locks up to increase fuel mileage. That will cause engine speed to drop noticeably. The converter will unlock if you tap the brake pedal. It will also unlock if you accelerate quickly. Sometimes a glitch in the throttle position sensor will trick the Engine Computer into thinking you're accelerating. That can cause the converter to unlock when it isn't really supposed. A misadjusted brake light switch can cause the converter to unlock intermittently, then relock a few seconds later.

Caradiodoc

Brake light switch or throttle position sensor are the two most likely suspects that I mentioned previously. The problem is we hate just throwing random parts at a problem without doing any diagnosis first. That is the most expensive and least effective way to solve a problem, however, the most effective way involves connecting a scanner to the car, then taking it on a test drive. Most people don't have access to a scanner so we have to resort to just trying new parts.

One simple thing you can try is holding the brake pedal up with your foot when the problem occurs. If that makes the problem stop, try readjusting the brake light switch. If the problem occurs more often at one specific speed or when you move the gas pedal just a little, suspect the throttle position sensor.

Some shops have a scanner that they can connect to your car that has a record / playback feature. You press the record button as soon as the problem occurs. Because the data travels through the scanner's memory, the recording actually begins a few seconds before you pressed the button. Later, the data can be replayed while watching for what caused the torque converter to unlock.

Of course, this all assumes that's what's happening. There really shouldn't be any noise associated with the converter unlocking unless the converter is what's causing the problem. A transmission specialist might be able to tell that on a test drive.

Another way to find the source of a noise is by using a tool called a "Chassis Ear". That is a set of six microphones, a receiver, and a set of head phones. Many mechanics have never heard of or seen this tool. You clip the microphones to suspect points under the car, then switch between them while listening with the head phones on a test drive. Moving the microphones around lets you zero in on the source of the noise. The tool costs $200.00 from Mac Tools. I can post a link to their web page that shows what it looks like if you need it. It's available from the other tool truck guys too like Matco, Cornwell, and Snapon.

Caradiodoc

That sounds a lot more significant than just an unlocking torque converter. There could be slippage taking place in the transmission's clutch packs. You would hear the engine pick up speed during shifts. This would be a good time to visit a transmission specialty shop. Typically they will test drive the car with you riding along. They should be able to provide a better diagnosis based on their observations.

Caradiodoc

DPFE sensor is a Ford item. No other manufacturer uses that.

You were talking about a noise at higher speeds. You're going to have to get someone to test drive your car so they can figure out what that noise is.

Caradiodoc

You can try changing the EGR sensor but it might just be reporting a problem to the Engine Computer. During a self-test while driving, there might not be enough exhaust gas flow. One possible cause is a passageway under the EGR valve clogged from carbon buildup.

Caradiodoc

I don't think you have a sensor problem. You need a professional diagnosis so you don't waste your time and money on the wrong parts.

Caradiodoc

Codes don't indicate specific parts. They point to the circuit or system with the problem that needs diagnosis. I don't have a listing for that specific code, but 400 codes pertain to the emissions system. The lower codes are EGR-related. Suspects are the valve, the sensor, or the passages could be blocked with carbon.

Caradiodoc

Smog pump, if one is used, is driven by a small belt on the front of the engine.

Why do you insist on changing stuff? That is by far the most expensive and least effective method to diagnosing a problem. You might not even have a defective part. There could be a corroded terminal in an electrical connector, a cracked vacuum hose, a leaking intake manifold gasket, carbon plugging an idle air passage. Etc.

You need to approach this like a doctor approaches an illness. They don't do a heart transplant then watch to see if that fixed the problem. They perform all kinds of tests first to rule things out and narrow down the list of possibilities. We aren't even sure yet what kind of noise you're hearing. That not only makes a diagnosis over a computer impossible, there's no way to make observations or perform quick tests. The codes you're getting could even be caused by nothing more than disconnecting things while the ignition switch was turned on. You might try disconnecting the battery for a few minutes to erase the codes, then see if they come back. If they don't, you may have been on a wild goose chase looking for a problem that doesn't exist.

Caradiodoc

Yup, I understand, but you want to solve this problem the best way possible and I don't think that is going to happen without having a professional who can stick his head under the hood. This isn't a simple or common problem.