idles high

[1970Custom]

Spent the past four days working to get my '93 back together.

Anyway I've got the clutch in and started it up and it idles way high.


Now a few details, first off the air box isn't attached so I'm wondering if that has something to do with it.

Second, when I replaced the clutch I noticed the Y pipe had some stress fractures that looked to be leaking so I decided to build myself another that would flow better and closely match the original with a few minor tweaks.

Those tweaks would be 2.5 from the manifolds back, and seeing as I couldn't get the two pipes merged close enough to the O2 censor I just plumbed it into one pipe (hasn't had the air tube attached for close to three years now). BTW it is LOUD. (2.5" glasspacks that are 12" long)

Now I was told on another forum that as long as its in one pipe it'd run just fine, however I'd like to know this from a few other sources as well.


Thanks for the help,

 

[blacksnapon]

While it's running, put your hand over the intake lightly, if the idle comes back down, its air leaks, or vacuum leaks.

 

[1970Custom]

Tried that to the best of my ability, didn't seem to solve anything.

 

[F150]

Base idle reset procedure? Or it may just need some more run time..........

 

[eco]

Assuming that this is a speed density system, a high idle is typically caused by a vacuum leak. Finding them can be like trying to find a needle in a haystack unless you have a smoke machine...now would be a good time to get one.

If the O2 is in ONE of the pipes, it will work, but not as effectively because the sensor is not seeing the whole picture of how the motor is running, it is only seeing half of the big picture. That, and the quantity of exhaust gases that pass over the sensor is cut in half, plus you incresed the size of the pipe so the velocity AND the temp of those gases has gone down (if you increase the inside diameter of a pipe AND the amount of gases passing through the pipe remains equal then the temp within the said pipe goes down). With the quantity of the gases and the velocity + temp of the gases down, the sensor will not get as hot (the O2 sensor needs to be HOT to function properly) as it would otherwise and that may or may not become an issue.