Questions and Answers

Pathfinder Bouncing Idle Q. Hi Vince. First off, my compliments on the great resource you provide. It almost makes me wish I had more problems with my car so I can look for a solution on your site (well, almost).

Anyway, I have a problem with a 1993 Pathfinder XE, 3.0 liter, automatic. It has about 220,000 kilometers on it and runs fine except for an intermittent idle problem. When coming to a stop, the rpm's drop until the car comes to a stop. At that point it may drop to 200 rpm or so and either bounce back up to about 700 or it will sit there for a few seconds shuddering. It has stalled only once in this state.

The problem first occurred a couple months ago. I took it to a local mechanic and he could find nothing wrong (having checked obvious things like vacuum leaks, EGR, etc.). He suggested I take it to dealership since he didn't have all the diagnostic equipment Nissan has. The dealer checked things out and could find nothing wrong. There were no error codes in computer.

Car seemed to be fine until a few days ago (miraculous healing?). This time, problem was more serious. I.e., it was happening *every* time I came to a stop (previous episode was on *many*, but not all stops). I took it to yet another mechanic. He suspected the "idler motor". Well, that turned out to be fine, so he checked vacuum, connections and grounds. Although the car misbehaved initially as he was working on it, it again healed itself and mechanic was unable to find anything wrong. Arghhh..

I now don't know what to do. It has new ignition components, good compression and fuel delivery, vacuum lines and wiring look okay, EGR and "idler motor" are fine. I therefore suspected an electrical problem so spent many hours peering at every bit of cable I could get to. I also opened all connectors I could find and cleaned them with contact cleaner. I was hoping one of them would have a loose wire or corroded pin, but found everything clean and intact. The car is running okay now (my head is not as I banged it on the corner of the hood, not once but twice... and in the same spot too).

I had new plugs, so installed them yesterday. I almost gave up on the one next to the firewall; I hope newer Nissans have a bit more room there. So, what else I can look for? I realize the main problem is that this is an intermittent problem, so tracing it can be done only when it's acting up, and the car seems to behave itself as soon as it sees a mechanic approach it. It *may* be related to moisture: the first time it happened it was a rainy day. The last time was not raining, but very humid. I hope you can suggest where to look or how to proceed. I am at a loss.

I don't know if this is significant, but should mention it anyway. The cruise control does not work. Indicator lights up on the panel, but nothing happens. Also, rpm's at speed don't always look quite right, although the car *seems* to be running okay: The tach shows maybe 2-400 drop or rise in rpm when the accelerator's position does not change. I don't *feel* a change in rpm's, but the tach says otherwise.

I hope you can point me in the right direction on this one. My sanity depends on it .. ;-). Thanks again for the service you provide. It's great.

Andy

A. I think this can be easily corrected by giving the throttle chamber a good cleaning. Take off the air inlet hose at the intake manifold and look inside. You will see the throttle plate there. Get some carburetor cleaner and clean it out. Also remove the IACV-AAC and clean inside the passages. This could very well fix the problem.

If not, then there is a good chance the IACV-AAV itself is bad. And since it is intermittent it will be tough proving that.

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