The EGR is hooked to intake vacumm on my 88, not the throttle body. Front most vacuum connection on the manifold, through the vacuum connection tree and bracket mounted at the front of the manifold, too the EGR solenoid, just behind the ballast resistor inside the the left front fender well near the top (under hood) back through the vacuum tree to the modulator (I think it's called) to the EGR.
My modulator or maybe it's called a back pressure sensor. had a torn diaphram. which leaked vacuum.
The connector on my EGR solenoid disintigrated, which caused the solenoid to stay open (default with no power) which caused the EGR to open near idle, which made for a really poor idle and cause dit to stall alot at low RPM's.
The vacuum lines have numerous places where they can rub through or become damamged.
A tip, on all the Renix models, every vacuum line can be pluged at the manifold for a test (one at a time), motor actually doesn't any of them to function well. The MAP vacuum connection on the TB, is critical and needs to be connected.
Another tip, the smaller vacuum lines disconnected will run your idle up moderatly ( a couple few hundred RPM's). A damaged larger vacuum line may run it up to 1200 or more.
Many of the high idle problems, especially when they are intermittant can be traced back to the IAC. A little cleaning and a few drops of oil dripped behind the piston, often works wonders. Low voltage or poor connections will also affect the IAC. It needs all the juice it can get to work properly.
The intake manifold bolts do come loose.
The TB gasket shrinks and the TB top bolts need to be tightened sometimes.
Haynes actually has a better vacuum hose diagram than my FSM does.
