View Full Version : Idle problem

12-10-2004, 10:21 PM
99 cobra has just started an intermittent problem at start up. It does not hold any rpms. Any idea what is going wrong? It is not consistent nor does it only occur on really cold days. I have no major mods and no mods recently. Any suggestions are appreciated.

12-11-2004, 06:46 AM
If it is not throwing any codes then it's hard to say but most of the time it is the throttle position sensor... :)

12-11-2004, 10:42 AM
I had this issue on my 86 svo. The mechanic said it was an idle air bypass valve that had become dirty. I used intake cleaner and not carb cleaner and cleaned everything I could get to. The problem went away very quickly.


12-12-2004, 12:02 PM
There could be several things happening. The IAC could be dirty bit if it is persistant you will thow codes and the "Check Engine" light will come on. The PCV may need to be replaced. Considering the amount of motor oil that passes through the PCV they do not last very long. Also they tend to leak air at the elbow which allows un-metered air to enter the intake will cause hard starts when the motor is cold. For starters, I would inspect the throttle body for deposits as well. Over time, the oil vapors will crud up the entire intake, valves, EGR, IAC, throttle plates and spark plugs. Also, if you are going to clean the IAC, and throttle body, get some electrical parts cleaner and clean off the MAF sensor. If you cannot correct the idle problem by cleaning, there is another issue related to the ECU or chip. Ford does have a flash fix for this and is one of the service bulletins for the 99 + programs used in all of the Cobra's. I had very much the same problem with my 01 and it took alot of cleaning to correct it. Not only did I remove upper intake plenum, I also removed all of the fuel injectors so that I could get cleaner to the intake valves as well as spraying into the spark plug holes. I would not recommend going to that extent since I had other problems with the car (carbon build up causing excessive pinging). Had I known about the use of an oil separator on the PCV line, I would have saved myself the headache of excessive carbon in the motor. The car never ran better after all of that work and adding the oil separator to the PCV line.

12-13-2004, 08:14 AM
Thanks for the help guys. I cleaned the throttle body last year when I replaced the air filter with a k&N so it will be interesting to see how dirty it is after one year. I will clean everything up this week and see how it goes.