"late" model egr question

[jos51700]

My 96 neon was getting about 24mpg, I just figured it was the 300k on the motor.

One new crank sensor later, The mileage jumped to 32mpg! ( it had a code) this is what it was at 100k miles.

The cel persisted and I found another code: the vacuum line to the egr was unplugged. Plugged it in, still has cel, but mileage went back to 24mpg!

Any thoughts on why this is?
Any harm done leaving it unhooked?

I've noticed that 2nd gen neons don't even have egr, just a block off plate on the head. Now I'm curious. I'd prefer to keep it if I can get the mileage up again. The funny thing is, it should be HELPING mileage any way.

 

[bcschief]

After the repairs if you continue to drive the car the check engine light will go out after the car goes thru a complete drive cycle and it finds nothing else wrong. Or you can clear the codes with a scan tool. If your car is due for emissions inspection I would let it go out on it's own otherwise when you take it in for inspection it will fail because it has not gone thru a complete drive cycle.

Brian