First off, car details:
'99 Maxima GLE - 146k km

It's been serviced recently with the engine & transmission oil changed, and spark plugs being replaced. On a recent 800km road trip, it averaged 28.5mpg with A/C on and cruising at 70-75mph. So it seems to be healthy!

Now on to the problem:

Until very recently, the car was idling at around 800-900 rpms. And occasionally on idle (say when I was stopped at a red light), the engine would behave oddly. It is as if it was 'kicking'. I don't know how to explain it as I've never experienced it before. The rpm's wouldn't fluctuate but the car wouldn't idle smoothly either. You can feel the car 'kicking' or engine 'hiccuping' in the drivers seat. The first time I felt it, I thought someone tapped the car from behind. However, once you start driving away it seems fine.

Anyway, this phenomenon would occur occasionally at this particular idle speed.

Then, a week ago the alternator died on me while driving thru rural areas of Boston (Sudbury, Malborough, etc.. -- i'm currently visiting family in this area). This required the car to be towed to some shop and had the alternator replaced.

Anyway, after they did this, the CEL came on. I wanted to diagnose it so I followed hte procedure to extract the CEL code. It ended up being nothing, the code said nothing was wrong. So I reset it and the CEL went away.

Good times right? Well, in the process, I must have adjusted the idle speed because the car now idles at 500-600rpm. For the '99 MY, the screw on the ECU also adjusts idle speed as well as putting the car in diagnostic mode. I presume, while fiddling with the screw, I altered the idle speed.

Now, with this new reduced idle, the phenomenon I described earlier occurs EVERYTIME the car is idling. The car seems to be fine otherwise, it seems a tad lazy in terms of holding a high gear instead of down shifting when driving at 25-35mph on those rural MA roads (I think this is due to the ECU being reset so it has to relearn the driving patterns).

Has anyone experienced this and knows why it occurs? Is it dangerous for the engine or is it just a quirk of the VQ's of this vintage?

Also what should I set the idle at? It seems I can adjust by turning the screw by the ECU or by turning it near the TB under the hood. Is this true?


Thanks

 

mines is doing the same exact thing!!!!
it feels like someone with a really big steal toe boot came over and kicked my engine one or two times.. it started only when i was idling at a stop light .. then it started happening when Im driving and i have no clue what it is... ive searched this site for answers.. but haven't really come up with any clear answers

 

http://forums.maxima.org/showthread.php?t=512283

 

Thanks, i read that thread (as well as the FAQ and other relevant stickies at the top of the forum).

i'm not sure if my symptoms are hte same as theirs as some of them mention the steering wheel shakes, which doesn't happen to me.

 

ignition coils?
i had similar symptoms on my 99, turned out to be 2 bad coils and a bad injector, however i was throwing a misfire code....also i dont believe the screw on the ecu has anything to do w/ idle...my car always idles around 550 (when it reaches normal operating temp)

 

yeah, I'm not getting any codes.

As for the ecu screw adjusting idle, thats what the label says right around the screw. It shows the direction to turn the screw and that it will affect idle speed.

maybe its only on Canadian '99s?