Slightly rough idle after warmup / 2000 GT

[jayrw]

Lately after my car warms up I notice the idle is a bit rough to where I can feel it in the driver seat and the stick shift sort of wobbles, car is a 2000 GT w/ 60k miles , all stock, Ive been using 92 octane gas since I bought it 1.5 months ago, also when I'm at a stoplight sometimes ill notice the idle speed drops to nearly nothing for a brief period (2-3 seconds) then it goes back up to a normal idle, and for the first time today it actually died when at a stop light ,it fired right back up tho .. any idea what I might look at? The check engine light hasn't came on at all (yet). The car feels normal performance wise when im actually driving except for maybe a slight hesitation on take off, Thanks.

 

[mustanggt3685]

Check your IAC. They go bad all the time. Should be a $5 part at autozone.

 

[2000fordstanggt]

Check your IAC. They go bad all the time. Should be a $5 part at autozone.

try $50 for the off brand and around $80 for the motorcaft iac.


i would check your ignition system. plugs, cop..ect

my car was misfiring on one cylinder (with no cel) and the stick would shake at 40. just a thought..

 

[mustanggt3685]

My bad, typo. +1 on the plug issue as well.

 

[eliteJAE]

so im guessing the acceleration isnt rough, or the higher RPMs neither? if its just the idle, then yeah check your IAC, try to clean it first, if that dont work go for a new one.

 

[jayrw]

Actually im noticing a slight loss in power as well ,it feels like im having to give the car more gas & clutch than usual in order to take off smoothly, otherwise it falls flat on its face ..sort of speak, can the IAC have anything to do with that?

 

[2000fordstanggt]

Actually im noticing a slight loss in power as well ,it feels like im having to give the car more gas & clutch than usual in order to take off smoothly, otherwise it falls flat on its face ..sort of speak, can the IAC have anything to do with that?

it still sounds to me like youre missing on one cylinder. i would check the plugs/cop's against the firewall on either side, i think 1 and 5, to start with. unplug the cop's one at a time, when you dont get a change in idle youve found it.

 

[jayrw]

it still sounds to me like youre missing on one cylinder. i would check the plugs/cop's against the firewall on either side, i think 1 and 5, to start with. unplug the cop's one at a time, when you dont get a change in idle youve found it.

Hm I figured the CEL would come on if it was missing a cylinder, Ill check it out Thanks.

 

[R.J.]

You can check the coils with an ohm meter. The primary resistance (betweem the two terminals) should be @.55 and the secondary (between the spring and the terminals) should be @5K. I just did mine for the same idle issue and they were .8 and 5.31K. Since they are all the same I don't think it is the problem.
I continued the troubleshooting steps in the Haynes manual and my EGR PDFE is not increasing signal voltage when the car gets hot. It should start around .2-.4 and increase to 4.0-5.0 at operating temp. Mine is staying at 1.03 all of the time. Just my .02
PM me if you don't have a manual and I can walk you through the check.