Rough Idle

Why Does My Car Idle Roughly At Low RPM?

[HS] My experience shows all NSXs have a VTEC rough spot around 1,500 RPM — hot or cold. This is not a problem.

[BSD] I have felt roughness in the engine at just off-idle speeds before. This combined with the way the clutch grabs sometimes results in less than smooth launches. However, if the roughness can be felt in the steering wheel as a primary vibration, then that is much worse than what I have felt. I mean, the steering wheel vibrates just a smidge on its own for any of the car’s vibrations, but if you actually feel it without thinking about it, something is a bit more wrong.

[KP] It’s something to do with the cams/computer/timing that, for whatever reason, Honda never quite resolved.

New owners have frequently noted this anomoly to the list only to be reassured that it is perfectly normal;. In everyday driving, it is completely transparent and you would likely never notice it. (I don’t and I’m very anal about these things!) Where you WILL sometimes notice this is on a cold start when the car will want to high-idle in this effected RPM range. In this scenario, the *idle* may appear to be rough and I would tell you that this is normal.

If, however, you have noticed a rough idle on an NSX that is warmed up and is idling roughly at an rpm of 800-1000, I’d say that this is NOT normal.

[CMI] I had a problem with my 95’s idle this summer. Took it in and they replaced an O2 sensor and adjusted the base idle. Covered under warrantee and no problems since.

[JCR – 2000/9/22] When I bought my car (’91 with 88,000 miles) it had a rough idle, so I talked to a friend who has his own auto repair business and specializes in engine diagnostics (I used to work for him a long time ago). He suggested that I remove the air cleaner and squirt carburetor cleaner directly into the air inlet body. He said that he gets in cars all the time with rough idle and it’s caused by some small amount of dirt or crud sticking to the mass air flow sensor and/or some of the other sensors that hang in the air stream. I did this, then started the car and it idled just fine. That was almost 18 months ago and it still idles smoothly, although I’ve only driven about 6000 miles in that time.