Hello all, frist time posting. First off I have a 2000 s2k which I bought used a couple months ago. It has a rebuilt engine and 168k miles. When I drive the car and prepare to stop, say, at a red light or a stop sign, the engine will go back down to idle speed but it will go a couple 100 rpm under what it is suppose to be and make a "a rum rum" sound and then go back up to the proper idle speed. Sometimes it gets so low that on the tach there are only 3 "lines" measuring the rpm. My question is what is causing the problem and if I can fix it myself, as the engine was already rebuilt 6 months/10k miles ago by the previous owner.

 

Double check hoses and the air filter. Perhaps the IAC needs a tweak?

 

I checked the air filter and its filthy. I think its a K&N filter so I'm going to clean that or if it isn't i'll just change it. Im going to check/clean the IAC later this week when I have some time and when you say double check the hoses what specific hoses are you recommend I check?

 

Mine does the same, rarely, but it does happen.

First time I saw my MAP sensor connector wasn't full secured, so I pushed it in and zip-tied it. I have still ran into this issue even after securing the harness. My PCV is clogged (which I am replacing today). I've already cleaned my idle air control valve.

I'm not sure what else to check, although like I said the problem is rare and intermittent.

 

I have a similar problem too, it happens maybe once in awhile. I always thought it was just bad gas

 

Do you have a check engine light?

 

nope check engine light has never came on since I had the car.

 

As someone else previously stated, check your IAC

 

Ok I just cleaned the air filter and the IAC. The IAC was really dirty and I cleaned it. This lessened the intensity of the bogging but it still bogs. It use to bog down by 500 or so rpm now it only bogs 100-200 rpm. Im going to clean the IAC again tomorrow and do a more thorough job as I half assed it.