Bob Paulson Posted May 1, 2017 Share Posted May 1, 2017 My 1990 Reatta has a problem with the idle. It can be set by the mechanic and a few days later it starts to climb. Currently it is idling at 1500 rpm. I've got to stand on the brake pedal to keep from creeping forward. I'm located in the SF Bay Area can anyone recommend a Reatta specialist nearby? Link to comment Share on other sites More sharing options...
Ronnie Posted May 1, 2017 Share Posted May 1, 2017 Hi Bob. Welcome to the forum! I can't recommend a mechanic in your area but I might have some information that your mechanic can use. The 3800 engine in your Reatta doesn't have an idle adjustment the way some older cars do. There is a throttle stop screw that can be adjusted to keep the throttle plate from sticking in the throttle bore but it isn't intended to be used as an idle adjustment once it is set at the factory. Any adjustment made to it when the car is running to set the idle will be overridden the next time the engine is started. The 3800 has an Idle Air Controller (IAC) that s constantly adjusting the air that goes into the throttle body to keep the RPM at the proper level. The RPM adjustment will be changed by the Engine Control Module (ECM) by it commanding the IAC to allow more or less air into the engine based on engine temperature and load placed on the engine by the AC or power steering pump. As you can see it is more complicated than simply adjusting a screw. Two common causes of an erratic or fast idle are a vacuum leak or a dirty IAC. It is possible that the IAC has failed but it is rare for that to happen. First thing I would do is look for broken or leaking vacuum lines. It is very common for the hoses to be in bad condition due to the age of these cars. Below are photos of the locations that should be checked for vacuum hose leaks. There is also a possibility that the intake manifold gaskets are leaking vacuum causing the RPM to be higher than normal. The next thing that should be done is cleaning the IAC and the passageway it goes into. Be sure to clean where the IAC seats at the bottom of the hole it mounts into. Instructions for doing that can be found here: IAC Cleaning Instructions Link to comment Share on other sites More sharing options...
Ronnie Posted June 1, 2017 Share Posted June 1, 2017 What was the outcome of this problem? The curiosity of a followup would be appreciated. Link to comment Share on other sites More sharing options...
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