RPM pulse... is it just cold?

[MatthewDavid]

Hello fellas... ok when I got into our 97' mark today it was running really weird... the rpm's are pulsing... to the point it almost pulls the car forward... does it in gear and in park... just doesn't pull in park ... but yeah never had this happen before... but it was 16 degrees out... does that have anything to do with it?... it's been running really good lately too... cept the low engine coolant light popping on... nothing smells funny... there's no leaks... just baffled!

 

[NateRW21]

I'm not familiar with Marks... My first guess would be IAC, or maybe a vacuum leak. I'm sure someone else with more mark specific knowledge will chime in!

 

[MatthewDavid]

Yeah I did some more research and I found that it's probably the IAC but there's also a wiring harness that could be faulting out... has anyone else heard of this?

 

[chicken]

was your defrost on? it could be the ac compressor cycling, if it cycles fast it could be low on freon