weird cold/warm start ups

subru92svx · #1 03-28-2007, 03:57 AM

My car is acting a little weird on cold and warm start ups. When I start my car after its been sitting overnight it starts right up and rpms go up to about to about 1500 like usual until car warms up, but while its warming up I can here the motor reving up and down spiratically until its warm. Then it just idles normally. I don't remember it doing this in the past. Then sometimes on warm start ups I'll start the car and the rpms shoot right up to about 2500 then drop way low to about 100-200 and the car almost dies, but never actually does. I thought it might be the cts so I replaced it with no change in motor. Now I'm thinking it might be my MAF sensor. I have 140,000 miles on my car with the original MAF sensor. I know a lot of people have replaced theirs on higher mileage cars thats why I was kind of thinking that might be it. I already cleaned it with the recommended MAF cleaner and it didn't seem to help. Any help,suggestions, or ideas would be great. Thanks

Manarius · #2 03-28-2007, 06:48 AM

I don't think it's the MAF sensor. Things would be a lost worse than wacky RPM if the MAF sensor was broken or getting bad readings. Good idea when you replaced the Coolant Temperature Sensor - but surprising it didn't fix things. I wonder if maybe you have a bad knock sensor or two - this could affect the RPM as the engine has to retard timing if it reads knock.

subru92svx · #3 03-28-2007, 12:12 PM

Well I just replaced both knock sensors about 15,000 miles ago. I was getting a code for one of them being bad so I just replaced them both. When I got them out off the car one had a nice big crack in the outer plastic layer. So I installed the new ones and haven't had the car throw another code yet.