IAC opens when cold
 

Lately it's been around 30F. Sometimes the IAC opens all the way making the engine idle around 2000rpm. This is especially annoying when I'm driving and it doesn't like to slow down.

Could it be the IAT? It runs just fine and idles normally after it warms up.

How did you determine it's the IAC and not something else like an intermittent vacuum leak?

Sounds more like a TPS issue with a coincidence of cold weather thrown in.

I would have to agree with Cruiser, usually if an IAC goes bad or gets dirty they will cause a no idle condition when it gets colder out. The vehicle will only stay running if you keep your foot on the gas until the engine reaches operating temp. High idle from what I have dealt with in the past was caused by a bad TPS. I'd start my XJ up after it sat all day at work and it would shoot right up to 2K. Shut the XJ off and wait few seconds then restart and it would be fine. Since replacing the TPS it no longer does this. 30 degree starts in the morning for a few weeks now and no issues.

Cowl intake. It sounds like a vacuum when I first start it up, then it normally goes away. Or it gets louder and sounds like a few vacuums.



I'll replace the TPS later today and get back on here.

Could be sticking in the cold. Cleaning it up might not hurt, but that's sometimes 50/50, might have to replace it.

No, it clearly opens. Normally it's a light sucking sound. When it opens further it sounds like it's trying to suck up the whole world