Irratic Idle

nsx24 · 23 February 2004

I have a 1991 with 69k, I just started it today after 2 months and let it warm up to temp and started to drive it but everytime it goes to a idle it drops below 500rpm then bounces up to 1000rpm. It will not steady out, but just just keep dropping then bouncing back up. Checked all the fluid levels and everything seemed to be fine. Any help would be appreciated.
Thanks

nsxexotic · 23 February 2004

just a guess. Idle air control valve or perhaps air in the coolant.

Larry Bastanza · 23 February 2004

nsx24,

Are you saying (1)that if the cars is running the engine is constantly roaming, or (2)every time you come back to idle it "dips" to 500, then comes to 1000rpm??

The first symptom is typical of a vacumm leak, broken/split vacumm line.

The second symptom is the sign of a dirty throttle body.

HTH,
LarryB

NSX-Racer · 24 February 2004

For this "sawtooth" behaviour there's a special procedure that may fix it. I had this with my '98 TBW too. As your car is a non TBW the procedure is of course a bit different but you may find it in the online service manual published in Lud's FAQ. Roughly it's adjusting the base and fast idle valves with resetting the ECU afterwards (pull clock fuse).

You may have also an error code - did you check?

demigod · 24 February 2004

Mine does the same thing when I just start the car to warm up. It goes away after its warmed up and ran a bit though.

nsx24 · 15 March 2004

cleaned throttle body and pulled ECU and now everything is fine.
Thanks guys

Spencer · 15 March 2004

nsx24 said:
cleaned throttle body and pulled ECU and now everything is fine.
Thanks guys

How do you clean the throttle body? Just curious...

DannyC · 17 March 2004

I am also curious on how to clean the throttle body. Is it difficult, and what to use?

Regards,
Danny

NSX-Racer · 17 March 2004

As I can recall my techie used an ultrasound cleaner. I think cleaning gasoline may work too.

matteni · 17 March 2004

I have always used and was instructed by Barn man to get a can of carb cleaner from the auto hardware store.

Basically on my 91 - I remove the air filter - start the car - and using the tube on the can of cleaner spray a little into the throttle body (I use short bursts and do it so that I get all the junk off the sides).

With my other hand I manually manipulate the throttle so the car does not stall out with each spray. I do this for 5-10 mins.

Problem I have is I have a KN filter and a theory. I believe the oil is clogging up the throttle body and by spraying the carb cleaner I am getting rid of the oil residue in the body but over time I have fouled up my plugs to the point that they need premature replacement.

So this time I am going to replace the air filter back to stock, clean the throttle body, replace the plugs, check the valve timing and then go ahead and have the fuel injectors bench tested and rebuilt to OEM flow standards. After that I will reset the ECU through the clock fuse and hopefully will have the smooth idle I am expecting back.

Soichiro · 17 March 2004

>>I have is I have a KN filter...

Nick repeat after me:

STOCK IS BEST //// STOCK IS BEST //// STOCK IS BEST

Your idle should be fine now.

Irratic Idle

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