Idle

I just bought a 85 pathfinder and the idle surges back and forth from 1000 rpm to like 2000 or more .Anyone have any suggestions ? Thanks !

1987 was the first year for Pathfinders. Check that sales slip again. ;)

On the idle note: nope, sorry. Something's wrong with the engine. A diagnostic service may reveal what's wrong with it. It doesn't sound like anything specific that I've heard of before.

You are correct I meant 87 . But thanks anyway !

Have you checked the sensors? Try checking the IAT (Intake Air Temperature) sensor mounted on the air intake tube next to the air filter, and the ECT (Engine Coolant Temperature) sensor. There may be a loose connection somewhere giving the ECU sporadic erroneous readings, which may cause the surging idle you describe. Or maybe one of the sensors is going bad.

Is the idle also rough? Does the engine misfire? Does it sound like the idle speed is affected by a change in the fuel mixture (rich/lean), or spark timing?

I bought a '95 pathfinder a few months back and it does the same thing, not quite as drastic as you are saying but like a 350 rpm up to 500 rpm jump......I was semi-curious as to what it was so I looked around online for info regarding that specific idle problem and it turns out that it is a common problem with pathfinders to do that. There were a few different reasons listed and the main one was the timing likes to jump for no reason after about 95,000 miles....another problem that was common was the IAT and the ECT problems that Hawaii 5-0 had mentioned....I am yet to fix mine but when I do I will tell you what it was and how to fix it

Check your AAC valve (Auxilary Air Control valve) round gold thing with a connector to it. Clean the carbon buildup