Thanks Gilbert, your insight is great as usual.
I think I've got to the bottom of this now. I don't believe my car has the EGR solenoid.
As always, I am happy to help where I think I can add value.
On our 73 Mustang Convertible we have a 302 2v engine with C4 auto tranny. The 302 is equipped with an EGR Valve, which is fully function (and, yes, connected). We purchased this Mustang about 3 or 4 years ago in our local area (Pittsford, suburb of Rochester, NY). This is a True Survivor, asits 2nd owener's family put the car inside a barn and it sat there for over 45 years. The 2nd owner got it as a nearly new vehicle (prior owner bought it and within weels traded it in for a truck). The 3rd owner purchased it 45 years or so later when the family of the 2nd owner decided to sell the farm and retire. Lynda and I bought it for asking price on the spot, as we knew the chances of finding another True Survivor like this with just over 19,000 original miles would likely never happen.
As I began to drive it I noted it had a dumble or bog on light acceleration. A hesitation on acceleration is often an accelerator pump issue, but in our case the acceleratir valve was working properly. Another common cause is ignition time is retarded dfrom spec, or the distributor vacuum advance diaphragm is leaking or ruptured.. I found the ported vacuum was reaching the diaphragm, and the vacuum diaphragm was not leaking. Yet another cause of a bog is an EGR Valve that is opening too soon (or at all on some engines). I
temporarily disconnected the vacuum signal hose from the EGR Valve and found there was sifference in the bog. So I plugged the EGR vacuum hose back into place. I then surmised the carburetor float level must be too low, so I popped the top off the carburetor and found it was about 1/4" too low. I adjusted the float level and went for a drive. Fixed...
Anyway, the reason I shared the above pararaphs is because I know a lot of fol disable and/or remove their older EGR systems, because they feel introducing exhaust gas into the intake manifold makes no sense. And at first bluch it sure does seem ro be an idea bestr left to have never been had. But, esentially exhaust gas is a quickly available inert gas. By introducing inert gas into the combustion chamber along with the regular air/fuel used to but, the combustion chamber temperature during the power stroke of the engine is reduced in comparison to an engine with no EGR recycling feature. The reduced temperature comes along with a reduction of pressure in the combustion cycle. This reduced the NOx level in the exhaust emission of the engine with the EGR Valve device.
In my years working on a lot of different Ford engines equipped with an EGR sytem, most engine ran just fine with them left in their functioning operation. There were a few engines that the EGR Valve would cause a bog on acceleration or sluggish low end performance. But that was more the exception, and often I could overcome that problem by adding 2 degree of ignition timing advance (before computer controlled engines) I have not seen where an EGR system had caused a significant problem, not do damage to an engine. Also, in some engines where the EGR was not functional the engine would produce pinging on light to medium, acceleration - something I tried to eliminate any time I could do so legally. So, if your engine is running well with the EGR system functioning I recommend leaving well enough alone. My two cents...
). Pictures of it would be great if anyone has any.
![IMG_3574[1].JPG](https://cdn.imagearchive.com/7173mustangs/data/attachments/90/90832-aa2eade86b0a6768f39694283c94b35b.jpg "IMG_3574[1].JPG")
