Trekintosh Posted September 26, 2019 Share Posted September 26, 2019 Greetings, Got my 98 legacy and ever since I got the car when the engine is warmed up and idling, it hunts around for different idle speeds. It’ll idle at 5-600rpm, then it’ll go up to 900, sit there for a few seconds, then go to 1050rpm and sit, then drop to 500, etc. it’ll try different RPMs, stay there for a few seconds, then try a different one. There are no error codes on my scanner, nor is there any status lights on the dash (except ABS, but that’s not relevant here I’m sure.) To me this speaks of some kind of sensor giving erroneous readings and the ECU is trying to acquire a baseline. Is that right? Where should I start with diagnostics? Cleaning the MAF? Thanks in advance for any help. Link to comment Share on other sites More sharing options...
doublechaz Posted September 27, 2019 Share Posted September 27, 2019 Could be your O2 sensor is sluggish, but I think it is more likely that your Idle Air Control Valve is sticky. There is a procedure in the Service Manual for how to clean it, but I don't have that in front of me at the moment. Link to comment Share on other sites More sharing options...
wtdash Posted September 29, 2019 Share Posted September 29, 2019 +1 on the above. Tune ups, vacuum leaks, etc. are also causes. What's the maintenance history? Link to comment Share on other sites More sharing options...
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