Just the other day for the first time i noticed that after i warmed up my car on a 30 degree morning, that once it reached normal operating temps it would occasionally drop down to 550 rpm then immediately pop back up to 750. I didn't think anything of it at first. Until it happened again yesterday and just this morning as well.

My car isn't throwing any codes and the only thing i can think of currently is maybe spark plugs? I have 67,xxx miles on the clock. I did recently have the bank 1 o2 sensor replaced about 2 months ago.

I was also contemplating taking it in for a tune up. I've owned the car 1.5 years since it had 50k on it and I don't know the previous owners care of the car?

 

I had a 2000 Si that had the same problem. I took it to the dealership several times for the issue and it was never resolved. They adjusted the idle speed but it didn't work. If I cut the A/C on the idle would drop down for a second or sometimes I would just be sitting with my foot on the clutch and the idle would drop. The car was stolen before I was able to find a solution but I can tell you that the spark plugs and tune up didn't make a difference for me. Hope you find a solution!

 

It seems to have stopped neither friday or today has it done this. i'm still bringing the car in for a tune up anyhow. I'll change the plugs too. Idk what it is but it was wierd.

 

I bet you picked up some bad gas and now that it's run thru it is OK, if there were big rain storms in your area the station you got your fuel from could have got water in the tanks.

You weren't the first this happens now and then.

As far as having your car tuned, or what they call it these days you can do it yourself and pocket quit a bit of change, if they do a complete job all they will do is put 4 plugs in and change the air and fuel filters.

Price the parts the most expensive is the fuel and I don't think these newer models have fuel filters like they used to(in line) it is just a screen type in the fuel tank, which usually will last the life of the fuel pump and or car.

 

Yeah i just purchased new plugs and cleaned out the stock airbox and filter. Probably was the fuel, I refilled the tank the other day when it had stopped and had driven for a good amount of miles.

I'm not looking to go all crazy considering i'm trading this car in, in the spring for an new SI. It's just easier to keep it looking and running mint, less chances for the dealership to go "it needs this, this and this" and give me some ridiculous trade in.

Thanks for the help.