Mechanics unable to locate EGR valve in order to pass smog test

Other than testing the EGR valve, not many options. You really need a 4 gas analyzer to know what is coming out of the tailpipe. Otherwise you won't know if repairs have helped the problem.
When you say EGR numbers I'm not sure what you mean. Most of the time the test is for CO and HC gases, along with oxygen and Nox also in some areas. The EGR valve allows some exhaust gas to be recycled thru the engine and reburned. CO or HC could be high if the EGR system is not working.

code p 1340 refers to crank position sensor and camshaft position sensor signals out of sequence
the results of the pretest smog test at 2400 rpm suggest that the cam advance solenoid or system is failing
that will alter the sequence of the signals resulting in the code and failing of the smog test
as to answer you question , I am not convinced at this point but I consider the cam advance system to be at fault and would be testing in that area

What all have you replaced? And what is you hydrocarbon lvl?

it can be complicated to pass the smog test! check your gas cap. thats the most common reason for a fail! they will not tell you that. you can have it code read at any autozone or advance auto for free if your check engine lights on.[only] otherwise you're at the mercy of the only garage you trust. it may be a bad 02 sensor,you have 2 [cost around $75.00]each. it may be stopped up catalytac convertor,do you smell rotten eggs when driving or at idle? thats a sign of bad convertor. good luck and thank you for choosing fixya.com

CODE P1131 LACK OF HO2S 11 SWITCHING HO2S SIGNAL LOW INPUT. POSSIBLE CAUSES IS AIR INTAKE SYSTEM LEAKING VACUUM HOSES LEAKING OR DAMAGED. AIR LEAKS LOCATED AFTER THE MAF SENSOR MOUNTING LOCATION. BASE ENGINE MECHANICAL FAULT COMPRESSION VALVE TIMING. HO2S CIRCUITS WET OR OILY CORRODED OR POOR TERMINAL CONTACT. HO2S SIGNAL CIRCUIT OPEN SHORTED TO GROUND SHORTED TO POWER OR THE SENSOR HAS FAILED. LOW FUEL PRESSURE OR VECHICLE DRIVEN UNTIL IT WAS OF FUEL.POSSIBLE AIR LEAKS AT THE PCV VALVE OR AT THE RELATED HOSES.

When the EGR VALVE is clogged or malfunctioning, it can cause irregularities in engine performance such as rough idling or valve knock, indicating that the EGR valve should be inspected.
The EGR valve works by routing a small amount of exhaust back into the combustion chamber. When the temperature in the combustion chamber is too high, nitrogen oxides are produced, which combine with elements in the atmosphere to form smog. Introducing a small amount of exhaust into the system reduces the temperature in the combustion chamber, reducing the amount of nitrogen oxides produced.

Many EGR valves are mechanical, and simply have a small valve which opens to allow exhaust into the combustion chamber and closes when it is not necessary, and to keep the air mixture optimal for combustion. Some mechanical versions will not open until there is sufficient back pressure, ensuring that the valve will not be open when the engine is idle or warming up and needs a higher concentration of oxigen for combustion. Electronic EGR valves are also available, and use electronics to regulate the valve.

If the EGR valve is stuck open, it will essentially cause a vacuum leak, leading to inefficient combustion, rough idling, hesitation, and sometimes stalling in extreme cases. This is because the car cannot combust on carbon dioxide from the tailpipe — it needs atmospheric oxygen. If the combustion chamber is flooded with exhaust from an open EGR valve, it will not function properly. To check and see if the EGR valve is stuck open, have someone idle a parked vehicle with the brake on while you examine the plunger shaft to see if it is stuck open.
If the EGR valve is stuck closed, emissions of nitrogen oxides will rise, and the car may start to knock. Spark knock happens when the fuel mixture in the combustion chamber ignites before it has been reached by the explosion in the cylinder, resulting in a disruption of the engine timing. In this instance, the engine should be warmed up and revved to see if the EGR valve will move.

In both cases, simple repairs are possible. The EGR valve can be clogged, and a simple cleaning of a mechanical EGR valve may solve the problem. In the case of an electrically controlled EGR valve or a more complex mechanical problem, replacement of the valve may be needed. The EGR valve is an expensive motor vehicle component, and care should be taken to ensure that it needs to be replaced rather than repaired. A reputable mechanic should advise you appropriately.

Failure to repair or replace the EGR valve will not lead to a life threatening condition, although it will reduce the life of your car and increase the potential emissions. Especially in areas which require smog testing, an automobile with a malfunctioning EGR valve may not pass

HERE can find one video about this subject.

Hope help with this (remember rated this help) Good luck.

true the EGR can really make a change and it should have been the first thing too look at because its the cheapest and easy to install

If your 84 mustang is fuel injected, it has a check engine light. If it is carbeurated (like mine) it does not. 85 and up are EFI, 84 was the crossover year.

well nanifold is part of the emission and the egr repair both and save time re e testing it! you want it to go through first time with the above wrong it wont pass!!

CHECK AND CLEAN I.A.C SENSIOR