Engine idle bog, dip, studder, stalling, etc
 

This question gets posted a TON. The symptoms are any of the following:

Engine idle dips really low when coming to a stop, and car sort of "shudders" because rpms get down to 300-400 rpm.

When at a stop, after giving a small amount of gas, and then pushing the clutch back in, such as backing out of a parking space, etc, the engine idle dips low and almost stalls.

Any other variation of the above. I will add other specifics as they become available.


So now that this happens, here are the steps and solutions to this problem.


First, understand that our ECU is a "learning" ECU. It is taking readins from many different sensors and adjust timing and fuel mappings based on the readings it gets from these sensors. At times, the readings can conflict for one reason or another, and cause the ECU to become confused. This is THE MOST COMMON reason for this bogging idle.

When this happens, DO NOT give the car gas, as it makes it more difficult for the ECU to "relearn". This ECU confusion occurs most often when there is a big change in temp or humidity in the atmosphere.

So:

1. Give it a couple days. The idle problem will most likely go away on its own. Though keep in mind it can come back again when the same conditions occur again! This is normal for our cars!

2. If after several days, this problem is still constant, try the "map sensor whack" located here:
https://www.s2ki.com/forums/index.php?showtopic=209708
Also, securing the map with the "zip tie" method may help.

3. If this does not work, clean the IAC motor. I will provide more specifics and possibly pictures on how to do this if I can. When you clean the IAC motor, if you notice a lot of oil and very thick crud in the area, you may need to install a catch can or figure out why you're getting so much oil blow by into your TB area from the PCV.

4. If that still does not work, you may need to replace the map sensor. (this does happen!)

5. If that doesn't work, then you may need to replace the IAC motor, though generally, this causes a high and low erratic idle when it goes bad.

This is great info! Thanks!!

Good info...much appreciated. :thumbup:

BUMP

should be must read for n00bs

I have found that this complaint often comes in the spring, about when the switch from winter gas to summer gas occurs. The suggestion to wait before taking action can work as the weather and gasoline will change eliminating the condition.

On my car I have found tht cleaning the TB occasionally helps. I don't think I have a serious blow-by problem, but the cleaning after a few years still helps.

Interesting. I noticed this in my car about a month ago. It slowly went away. I thought it was almost going to stall a couple of times.

It went away and the car has been running great. 46k miles.

thanks for the info.

Great information, thanks for putting it together

I thought I read that you have to retrain the ECU when disconnecting the battery or the backup fuse by starting the car and holding the RPMs at 3K for 5 minutes. Is this true?

no when you reset the ECU disconnect the negative on battery, reconnect after 15 min or so then just turn the car on, and let the fan cycle three times.. some people like to drive it immediately after to begin the learning process but you dont have to