My 1992 mustang is having a few issues. I noticed the car was stuttering when starting up in idle. Looked at egr valve and unplugged it. Car idling better at roughly 700-1000 rpms. But when I put it in first gear, the car seems like it’s losing power. I changed o2 sensors, spark plugs, and fuel filter. I did drain the gas and put fuel injector cleaner. I put a code reader to it and no codes besides the egr error. Any ideas on what problem(s) it can be?
Get the engine up to operating temperature.
And while the engine is idling, take the handle of a screwdriver and rap on the Idle Air Control valve.
https://www.rockauto.com/en/moreinfo.php?pk=5403768&cc=1134054&jsn=468
If the idle speed changes, replace the IAC valve.
Tester
Stumbling at idle and an egr code? You’ve got to investigate the egr situation, as if it is sticking open a little that would be the symptom. The way I test the EGR valve on my Corolla of similar vintage — worked on my prior VW Rabbit and works on my 70’s Ford truck too – is I connect a hand-held vacuum pump to the EGR vacuum input and apply vacuum while the engine idles. That should open the EGR valve & stall the engine. Doesn’t prove the EGR isn’t sticking open a little at idle even so, but at least it proves the EGR pintle moves with applied vacuum. I don’t see where you post the code number or what the code is, but if it is something like EGR open when it should be closed, that has to be addressed. You may have to remove the EGR valve and inspect what’s happening on the other side you can’t see. Often there’s carbon deposits that need periodic cleaning in that area.
There’s a number of things that could cause a problem like this; including an EGR valve hanging open a bit. An IAC issue is also a very distinct possibilty.
Is this the 5.0 engine? Another possibility is the PCV hose crumbling. The hose is buried underneath the intake manifold towards the rear and is not easily accessible.
Does this engine use a diaphragmatic EGR solenoid? Did you verify that the solenoid is working properly. Elastomer diaphragms can get old and deteriorate, hanging up the valve.