Idles at 1500 rpm

[techdbw]

I have a 90 LX with 2.3 NA and T5. I set the idle at 800rpm with idle solenoid disconnected, when I plug in the idle solenoid the speed idle jumps to 1500 rpm. Can anyone offer some suggestions or is it supposed to idle this high?

 

[JamesBaumann]

http://projecthp.ford23.com/tech.html

Have that

 

[i4power]

There should be an adjuster screw on your throttle body. I can't really describe where it's at, but you can use a flathead to adjust up and down.

EDIT: Ahh, Stinger has that on his site.

 

[Ray III]

my car was idling at anywhere from 1500-3000 awhile back, it was pissing me off. And other driveability crap. Eventually I found out the MAP sensor was bad, if yours is, then unplugging it (on the firewall) should drop the idle and make the car run a LOT better, and then it's around 100 to get a new one

 

[JamesBaumann]

I have been having the same problem as you RayIII. Sometimes when my car idles it is perfect and smooth at 1000rpm. Sometimes it is around 1200rpm and seems to misfire itself. Sometimes it is up around 2000rpm. This makes no damn sense to me at all. I tried a couple different things to get it to idle properly, but with no success. I have yet to get my hands on a voltmeter, so I haven't been able to set it that way. However, I will soon. I have a feeling that it has something to do with the computer due to the erraticness of it. My problem is, I know nothing about vehicle computers, so I can't really manipulate mine to make everything run properly. Anybody have any links or anything where I could read up on these automotive computers (Our Mustang ones in particular) so I could learn something about them. Anyways, the point of this post is to ask where this MAP sensor that you speak is located. I know that it is on the firewall, but where exactly? Thanks for any help.

 

[i4power]

Well, you can't change the settings on the computer itself. What you need to do is to find what sensor is broken and change it.

 

[JamesBaumann]

Any suggestions? I am going to replace the 02 sensor, could that potentially be it?

 

[i4power]

Maybe your idle speed controller (IAC I think).

 

[JamesBaumann]

Isn't your IAC (Idle Air Control) just a plug in that you can unplug and plug back in as you want? I thought it was, therefore, I would not know how to adjust it.

 

[i4power]

You wouldn't adjust it...you'd replace it. It sounds to me like it's bad, because it's behaving erratically.

 

[JamesBaumann]

Thanks, I appreciate the help. I'll try setting my idle properly the best I can once I get my hands on a volt-meter. If my IAC is bad, how much does it cost to replace? Just lookin for a ballpark figure here.

 

[Ray III]

You can't set the idle. The computer takes care of that. Much like our Government takes care of us in exchange for uor freedom

Unplug the IAC and start the car. Turn the screw on the opposite side of the TB to open the throttle blade until you idle at 900 RPM. Theoretically, this should merely disable computer control of the idle; if it continues to run weird then that's not it so plug it back in.

The MAP (Manifold Absolute Pressure) sensor is located high on the firewall behind the valvecover or intake manifold, somewhere around there. It's an ~2"x3" black box with a wire connector and vaccuum hose on the bottom. Unplug the wire connector. If the car idles perfectly when you start it up, and runs decent, that is your problem.

You could have multiple problems. A major cause of misfire is bad spark plug wires, as I found out a year after replacing them with EL CHEAPO brand. You should have paid at least $30 for them (stock replacements not "race" wires), and taken care to route them so they don't rest on any grounds.