Afternoon guys

im having an issue with my car, that i wanted to get some feedback on


Problem

on cold starts, the car will sometimes idle rough for about 2-3 seconds. it appears as if its going to stall when it does this, as the RPM's will drop to about 500-600rpm's. after 2-3 seconds, the car returns to a normal idle

Frequency

it seems to happen once in a blue moon. it occurred today and happened about a week ago.

Symptoms
Rough idle, sounds like the car is misfiring then stops. No CEL and the car otherwise drives 100% fine. i even plugged in my scanner and just to see and everything came back normal. Oil level is normal.

Modifications to the car
berk TP, magnaflow catback, megan coilovers.

-im relatively mechanically inclined, so my first guess is that its the MAP sensor. however, i just wanted tot run the issue by you guys to see if theres anything else i should go about checking.

Thanks!

 

sounds like an iacv issue to me.. you can take it off and clean it and see if that happens. roughly how cold is ambient air?

 

[QUOTE=Tech7427,Oct 25 2009, 06:16 PM] sounds like an iacv issue to me.. you can take it off and clean it and see if that happens. roughly how cold is

 

Mine does it too. Honestly it'll run rough for the first couple minutes and then settle down. I've been wondering if the temp sensors are lying to the ECU.

 

Maybe the ECT (engine coolant temperature sensor). How many miles on your car?

 

16K. I have a feeling it sat outside for an extended period though. I've been meaning to hook the scanner up to it when cold to read the sensors. Just haven't done it yet.

 

The iacv can get stuck in the am if its gunked up with carbon.

 

Not to down play your issue, but the motor is cold, it's not going to run smoothly. To top it off it's a 4cyl so you'll feel it more.

I had this happen a few times in our TL. Parked out overnight in the 30-32f it would occasionally start, rev high and be a little rough. Once warmed up it all went away. 2-5 seconds typically. My S is completed garaged but when it's really cold out it revs high and isn't as 'smooth' but then again I keep it below 3K until it's completely warmed up. You should do the same.

If this problem is there after fully warmed up, check for codes, otherwise enjoy the car man and don't worry so much.

 

None of my other hondas, my subaru or my truck does this so, I don't think it's a general rule. That's one of the advantages of fuel injection over carbs. The computer can send the correct amount of fuel very early in the whole starting process. Heated 02 sensors are normally active within 30 seconds to a minute or so of startup.

It's very noticable as a slight stumble driving down the driveway. Once I get to the road, it's all but gone (1/4 mile or so).

I do agree it may be normal, I just wouldn't assume it is.

DBW doesn't have an IACV does it? I know on the subaru's, the transition to DBW meant goodbye IACV.

 

Im thinking ECT but 16K is pretty low mileage