This has been a long time in coming. I have a '91 240, 50-state legal model. It has an EGR system, but I don't know a thing about the system. Not to seem ignorant, but I have a few questions.

Things like, where is the EGR valve?

What is that little deal on the strut tower beneath the ABS modulator?

What exactly does it do?

Does it make noise? This is an honest question because I've been tracing a ticking noise for 50k, to no avail.

I only get a fault code from EGR when I disturb vacuum lines with the engine running, so this is more of a "what is the deal with this system" question, more than "something's wrong with this system". Besides, the fault code for EGR says only "EGR system faulty". No real specifics.

Any insight into the EGR system would be appreciated, since I'm in the dark about that part.

the egr valve is located under the intake manifold near the rear of the engine. it is shaped like a flying saucer and has a yellow plastic vacuum hose attatched to it. the gizmo on the strut tower is the egr controler. the controler has white and yellow plastic vacuum hoses atatched to it. the ezk116 (spark computer) operates the egr valve by driving the controler at specific frequencies depending on engine load. when the egr controler is activated, manifold vacuum is allowed to open the egr valve. the controler will make noise, although i've never had any one complain about it so i'm not sure if it can be heard inside the vehicle. the system diagnosis itself by watching the resistance change through the egr temp sensor. this sensor is located either in the pipe between the intake manifold and the valve, or it may be screwed into the valve its self. when the ezk116 tells the controler to open, the egr valve opens, and the hot exahust gasses flowing throughr the pipe heat the egr temperature sensor changing the temperature sensors resistance. this change in resistance is the conformation that the valve is open. if the ezk116 does not see expected resistance values through the egr temperature sensor, the check engine light will set and a dtc will be found in socket a6.

Thanks, Eric, that's exactly what I was looking for. I did get a check engine light one time, but it was because I pulled the yellow hose from the EGR control when I was doing something else.

That was the last gray area of my car. Thanks again.