I’ve had a problem with a high idle (2500 rpm) for about a year now. When I first got the car back with the 3.4L, it ran just fine; but after it’s first storage from winter, I started it up and it had a high idle, and it never got any better; or worse.
So I’ve been doing a lot of research on the subject, in the Pennock Fiero Forums (PFF), and saw that it is a common problem on Fieros. They are over twenty years old now, and a lot of the vacuum lines are plastic – and over time that plastic becomes brittle and cracks. Thus causing a leak.
So I inspected, for a good hour, all the vacuum line around the upper part of the engine (the most common place for the leak). But I found nothing :(
However, I went back to the laptop and read another post/thread in PFF talking about the EGR Solenoid and some of the problems it can cause. I went back out into the garage to take a look…
…Blammo! One of the plastic lines (very small) had been cracked. Take a look at the pictures below. I haven’t had a chance to fix/test this find, so I’m wondering if it is the cause. I hope it is, because it is an easy fix.