99 Cougar won't run in cold weather

I'm working on a 99 Cougar that idles rough and won't run at high rpm's when the outside temp drops below 20 degrees. We have tested every sensor and they all check fine. With the exception of the MAF, when we backprobed to get a volt reading, the SIG wire should have been at 4.5 volts, but we don't get any reading on the volts. The wire is not broken between the MAF and the PCM (ECM). When the outside temp gets above 30 or higher, the car idles and runs great. Could this be a plugged cat. conv.?

My wife has the same problem with her '99 Cougar. Have you found anything out about this problem?? Thanks for any help.

I'm having a similar problem but it's intermittent. The car will not idle or idles at low rpm. Doesn't seem to matter if the engine is warmed up or not. And then sometimes it just starts up and runs fine. It is a problem with the idle though and not running rpm. If I force it and get it going by keeping the rpm up, it runs fine except for tending to lose rpm too quickly when I back off the gas. I've been thinking vacuum line or fuel filter.

Can someone tell me where the fuel filter is.

I'm having a similar problem but it's intermittent. The car will not idle or idles at low rpm. Doesn't seem to matter if the engine is warmed up or not. And then sometimes it just starts up and runs fine. It is a problem with the idle though and not running rpm. If I force it and get it going by keeping the rpm up, it runs fine except for tending to lose rpm too quickly when I back off the gas. I've been thinking vacuum line or fuel filter.

Can someone tell me where the fuel filter is.

It is located in between passenger side door and that rear tire. Just look up under the car in front of the passenger rear tire, and you should see it. Also I have changed the fuel filter in this one and mechanics have told me it is a vacuum leak, but they can't find the leak. Someone has told me it could be major carbon buildup. I'm going to try and get rid of that this weekend.

I fixed the problem. If you all are having the same symptoms, I may have a fix for ya. The plastic pc on the front of the throttle body had a vacuum leak around it. The seal between it and the rest of the throttle body had broken. All I had to do was remove the plastic pc, take some silicone and make a new seal between them, then attach it back on. Now it runs like new. Hope that helps someone.:smile::smile::smile: