I've owned this car for just over two years and I have been noticing a couple things since I purchased it from a private party. The car has around 77,000 miles and has mostly all original parts. The vehicle still runs pretty good for it's age and I have had no major issues with it, however I noticed that the tachometer moves around quite a bit when the vehicle is stationary at a stop sign or in a parking lot. The rpms will randomly spike up to around 1000 rpms after the engine is at operating temperature and will then return to around 650 rpms. I have tried to see if turning off the ac or headlamps would fix what I was noticing, however it seems to persist regardless. The car also has an idle of around 1900-2000 rpms when I first turn it on. The idle has slowly been getting more erratic and it seems to be a problem that has definitely not been getting better. There have been a few times now where I have turned the car on and the car barely seems to stay running and I have to depress the accelerator pedal to keep the engine running. The rpms would rapidly jump between about 1000 and 2000 rpms and then drop down to around 400 rpms.
My question is 1) Is it normal for the idle to be at 1900-2000 rpms when I first turn it on? and 2) Is a rough/erratic idle something that I should be concerned about? Any insights or ideas of things to check on are very much appreciated.
Since it’s 20 years old at this point unless you have a scanner and can monitor inputs like mass air flow or throttle position I would start by just looking over and checking vacuum lines to check for any dry cracks or leaks. Carb cleaner or throttle body cleaners work good as well to spray on the vacuum lines and around the intake and just listen for idle changes
In addition to that, also clean the mass air flow sensor and throttle with some MAF sensor cleaner and throttle body cleaner. Odds are it's gummed up with stuff building up over 20 years.
